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Chinese Journal of Catalysis
2022, Vol. 43, No. 7
Online: 18 July 2022

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Cover: Qian Sun and co-workers in their review on pages 1547–1597 systematically summarize the fabrication strategies of single atom catalysts (SACs), introduce the CO2 electroreduction (CO2RR) applications of SACs and heterogeneous molecular complexes, discuss the advanced in situ/operando and ex situ characterizations techniques to reveal the in-depth catalytic mechanism and provide the future development of single atom-based catalysts (SACs, molecular complexes) for CO2RR.

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Special column on catalytic conversion of CO₂

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Preface to special column on catalytic conversion of CO2 Yanqiang Huang, Da-Gang Yu, Guoxiong Wang 2022, 43 (7):  1545-1546.  DOI: 10.1016/S1872-2067(22)64112-3 Abstract ( 249 )   HTML ( 3001 )   PDF (791KB) ( 191 )

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Single atom-based catalysts for electrochemical CO2 reduction Qian Sun, Chen Jia, Yong Zhao, Chuan Zhao 2022, 43 (7):  1547-1597.  DOI: 10.1016/S1872-2067(21)64000-7 Abstract ( 403 )   HTML ( 3513 )   PDF (13877KB) ( 575 )   Electrochemical CO2 reduction reaction (CO2RR), powered by renewable energy, emerges as a promising approach against environmental issues and energy crisis by converting CO2 into value-added chemicals. Single atom catalysts (SACs) with isolated metal atoms dispersed on supports exhibit outstanding performance for CO2 electroreduction, because of their strong single atom-support interactions, maximum metal utilization and excellent catalytic activity. However, SACs suffer from agglomeration of particles, low metal loading, and difficulty in large-scale production. In addition, molecular catalysts as another single atom-based catalyst, consisting of ligands molecules connected to metal ions, exhibited similar metal-nitrogen (M-N) active centers as that in metal-nitrogen-carbon (M-N-C) SACs, which were highly active to CO2 reduction due to their well-defined active sites and tunability over the steric and electronic properties of the active sites. Nonetheless, molecular catalysts are challenged by generally moderate activity, selectivity and stability, poor conductivity and aggregation. Many works have been devoted to overcoming these issues of SACs and molecular catalysts for efficient CO2RR, but only limited reviews for systematic summary of their fabrication, application, and characterizations, which were highlighted in this review. Firstly, we summarize recent advanced strategies in preparing SACs for CO2RR, including wet-chemistry approaches (defect engineering, spatial confinement, and coordination design), other synthetic methods and large-scale production of SACs. Besides, electrochemical applications of SACs and molecular catalysts on CO2RR are discussed, which involved the faradaic efficiency and partial current density of the desired product as well as the catalyst stability. In addition, ex-situ and in-situ/operando characterization techniques are briefly assessed, benefiting probing the active sites and understanding the CO2RR catalytic mechanisms. Finally, future directions for the development of single atom-based catalysts (SACs, molecular catalysts) are pointed out.

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Recent advances in fixation of CO2 into organic carbamates through multicomponent reaction strategies Lu Wang, Chaorong Qi, Wenfang Xiong, Huanfeng Jiang 2022, 43 (7):  1598-1617.  DOI: 10.1016/S1872-2067(21)64029-9 Abstract ( 267 )   HTML ( 466 )   PDF (1704KB) ( 274 )   Carbon dioxide (CO2) is the main greenhouse gas and also an ideal C1 feedstock in organic synthesis because it is abundant, non-toxic, nonflammable, and renewable. The synthesis of organic carbamates using CO2 as a phosgene alternative has attracted extensive attention because of the importance of carbamates in organic synthesis and in the pharmaceutical and agrochemical industries. In recent decades, many multicomponent reaction strategies have been designed for constructing different types of organic carbamate molecules. Most of these methods rely on the in situ generation of carbamate anions from CO2 and amines, followed by reactions with other coupling partners. Synthetic strategies for acyclic carbamates include nucleophile-electrophile coupling, nucleophile-nucleophile oxidative coupling, difunctionalization of unsaturated hydrocarbons, and C-H bond functionalization. Strategies for the synthesizing cyclic carbamates include carboxylative cyclization of in situ-generated unsaturated amines and difunctionalization of unsaturated amines with CO2 and other electrophilic reagents. This review summarizes the recent advances in the synthesis of organic carbamates from CO2 using different multicomponent reaction strategies. Future perspectives and challenges in the incorporation of CO2 into carbamates are also presented.

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Tuning strategies and structure effects of electrocatalysts for carbon dioxide reduction reaction Cong Liu, Xuanhao Mei, Ce Han, Xue Gong, Ping Song, Weilin Xu 2022, 43 (7):  1618-1633.  DOI: 10.1016/S1872-2067(21)63965-7 Abstract ( 397 )   HTML ( 409 )   PDF (6779KB) ( 366 )   Carbon dioxide emissions have increased due to the consumption of fossil fuels, making the neutralization and utilization of CO2 a pressing issue. As a clean and efficient energy conversion process, electrocatalytic reduction can reduce carbon dioxide into a series of alcohols and acidic organic molecules, which can effectively realize the utilization and transformation of carbon dioxide. This review focuses on the tuning strategies and structure effects of catalysts for the electrocatalytic CO2 reduction reaction (CO2RR). The tuning strategies for the active sites of catalysts have been reviewed from intrinsic and external perspectives. The structure effects for the CO2RR catalysts have also been discussed, such as tandem catalysis, synergistic effects and confinement catalysis. We expect that this review about tuning strategies and structure effects can provide guidance for designing highly efficient CO2RR electrocatalysts.

Special column on catalytic conversion of CO ₂

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Progresses on carbon dioxide electroreduction into methane Han Zheng, Zhengwu Yang, Xiangdong Kong, Zhigang Geng, Jie Zeng 2022, 43 (7):  1634-1641.  DOI: 10.1016/S1872-2067(21)63967-0 Abstract ( 771 )   HTML ( 347 )   PDF (2415KB) ( 509 )   The conversion of CO2 into value-added chemicals and fuels via electrochemical methods paves a promising avenue to mitigate both energy and environmental crisis. Among all the carbonaceous products derived from CO2 electroreduction, CH4 is one of the most important carriers for chemical bond energy storage due to the highest value of mass heat. Herein, starting from the proposed reaction mechanisms reported previously, we summarized the recent progresses on CO2 electroreduction into CH4 from the perspective of catalyst design strategies including construction of sub-nanometer catalytic sites, modulation of interfaces, in-situ structural evolution, and engineering of tandem catalysts. On the basis of both the previously theoretical predictions and experimental results, we aimed to gain insights into the reaction mechanism for the formation of CH4, which, in turn, would provide guidelines for the design of highly efficient catalysts.

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Efficient hydrocarboxylation of alkynes based on carbodiimide-regulated in situ CO generation from HCOOH: An alternative indirect utilization of CO2 Shu-Mei Xia, Zhi-Wen Yang, Kai-Hong Chen, Ning Wang, Liang-Nian He 2022, 43 (7):  1642-1651.  DOI: 10.1016/S1872-2067(21)63848-2 Abstract ( 158 )   HTML ( 365 )   PDF (1310KB) ( 215 )   Supporting Information The role of carbodiimide as dehydrant in the chemo-, regio- and stereoselective Pd (II/0)-catalyzed hydrocarboxylation of various alkynes with HCOOH releasing CO in situ is reported for the first time to obtain α,β-unsaturated carboxylic acids. Both symmetrical and unsymmetrical monoalkynes show good reactivity. Importantly, 2,2’-(1,4-phenylene)diacrylic acid can also be synthesized in high yield through the dihydrocarboxylation of 1,4-diethynylbenzene. Besides, an excellent result in gram scale experiment and TON up to 900 can be obtained, displaying the efficiency of this protocol. Notably, regulating the types and concentrations of dehydrant can control the CO generation, avoiding directly operating toxic CO and circumventing sensitivity issue to the CO amount. On the basis of the attractive features of formic acid including easy preparation through CO2 hydrogenation and efficient liberation of CO, this protocol using formic acid as bridging reagent between CO2 and CO can be perceived as an indirect utilization of CO2, offering an alternative method for preparing acrylic acid analogues.

Special column on catalytic conversion of CO₂

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Photo-catalyzed sequential dearomatization/carboxylation of benzyl o-halogenated aryl ether with CO2 leading to spirocyclic carboxylic acids Yaping Yi, Chanjuan Xi 2022, 43 (7):  1652-1656.  DOI: 10.1016/S1872-2067(21)63956-6 Abstract ( 184 )   HTML ( 344 )   PDF (1066KB) ( 504 )   Photo-catalyzed tandem dearomatization/carboxylation of benzyl o-halogenated aryl ether with CO2 was achieved, which affords spirocyclic carboxylic acids under mild conditions. The reaction has good functional group tolerance with high yields. Mechanism studies indicate that the transformation was realized via intramolecular radical addition and nucleophilic addition.

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S-Scheme 2D/2D Bi2MoO6/BiOI van der Waals heterojunction for CO2 photoreduction Zhongliao Wang, Bei Cheng, Liuyang Zhang, Jiaguo Yu, Youji Li, S. Wageh, Ahmed A. Al-Ghamdi 2022, 43 (7):  1657-1666.  DOI: 10.1016/S1872-2067(21)64010-X Abstract ( 221 )   HTML ( 282 )   PDF (6861KB) ( 265 )   Supporting Information Reducing CO2 to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO2 emissions and addressing resource depletion. Nevertheless, severe charge recombination and the high energy barrier for CO2 photoreduction on the surface of photocatalysts compromise the catalytic performance. Herein, a 2D/2D Bi2MoO6/BiOI composite was fabricated to achieve improved CO2 photoreduction efficiency. Charge transfer in the composite was facilitated by the van der Waals heterojunction with a large-area interface. Work function calculation demonstrated that S-scheme charge transfer is operative in the composite, and effective charge separation and strong redox capability were revealed by time-resolved photoluminescence and electron paramagnetic resonance spectroscopy. Moreover, the intermediates of CO2 photoreduction were identified based on the in situ diffuse reflectance infrared Fourier-transform spectra. Density functional theory calculations showed that CO2 hydrogenation is the rate-determining step for yielding CH4 and CO. Introducing Bi2MoO6 into the composite further decreased the energy barrier for CO2 photoreduction on BiOI by 0.35 eV. This study verifies the synergistic effect of the S-scheme heterojunction and van der Waals heterojunction in the 2D/2D composite.

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Visible-light photoredox-catalyzed carboxylation of benzyl halides with CO2: Mild and transition-metal-free Ke Jing, Ming-Kai Wei, Si-Shun Yan, Li-Li Liao, Ya-Nan Niu, Shu-Ping Luo, Bo Yu, Da-Gang Yu 2022, 43 (7):  1667-1673.  DOI: 10.1016/S1872-2067(21)63859-7 Abstract ( 1209 )   HTML ( 290 )   PDF (1351KB) ( 876 )   Supporting Information The visible-light photoredox-catalyzed carboxylation of benzyl chlorides and bromides with CO2 has been reported. With inexpensive organic dyes as photocatalysts and amines as electron donors, this carboxylation proceeds well in the absence of sensitive organometallic reagents, transition metal catalysts, or metallic reductants. A wide range of commercially available and inexpensive benzyl halides undergo such carboxylation to give valuable aryl acetic acids, including several pharmaceutical molecules and drug precursors, in moderate to high yields. Moreover, this reaction features mild reaction conditions (one atmospheric pressure of CO2 and room temperature), broad substrate scope, good functional group tolerance, easy scalability, and low catalyst loading, thus providing an efficient approach for the assembly of aryl acetic acids.

Special column on catalytic conversion of CO ₂

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Regulating surface In-O in In@InOx core-shell nanoparticles for boosting electrocatalytic CO2 reduction to formate Yan Yang, Jia-ju Fu, Tang Tang, Shuai Niu, Li-Bing Zhang, Jia-nan Zhang, Jin-Song Hu 2022, 43 (7):  1674-1679.  DOI: 10.1016/S1872-2067(21)63943-8 Abstract ( 262 )   HTML ( 219 )   PDF (2998KB) ( 181 )   Supporting Information To solve the excessive emission of CO2 caused by the excessive use of fossil fuels and the corresponding environmental problems, such as the greenhouse effect and climate warming, electrocatalytic CO2 reduction to liquid fuel with high selectivity is of huge significance for energy conversion and storge. Indium has been considered as a promising and attractive metal for the reduction of CO2 to formate. However, the current issues, such as low selectivity and current activity, largely limit the industrial application for electrocatalytic CO2 reduction, the design optimization of the catalyst structure and composition is extremely important. Herein, we develop a facile strategy to regulate surface In-O of In@InOx core-shell nanoparticles and explore the structure-performance relationship for efficient CO2-to-formate conversion though air calcination and subsequent in situ electrochemical reconstruction, discovering that the surface In-O is beneficial to stabilize the CO2 intermediate and generate formate. The optimized AC-In@InOx-CNT catalyst exhibits a C1 selectivity up to 98% and a formate selectivity of 94% as well as a high partial formate current density of 32.6 mA cm-2. Furthermore, the catalyst presents an excellent stability for over 25 h with a limited activity decay, outperforming the previously reported In-based catalysts. These insights may open up opportunities for exploiting new efficient catalysts by manipulating their surface.

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Regulating Pd-catalysis for electrocatalytic CO2 reduction to formate via intermetallic PdBi nanosheets Linfeng Xie, Xuan Liu, Fanyang Huang, Jiashun Liang, Jianyun Liu, Tanyuan Wang, Liming Yang, Ruiguo Cao, Qing Li 2022, 43 (7):  1680-1686.  DOI: 10.1016/S1872-2067(21)63999-2 Abstract ( 234 )   HTML ( 201 )   PDF (5113KB) ( 249 )   Supporting Information Electrocatalytic CO2 reduction plays an important role in the reduction of the CO2 concentration in atmosphere and consequently the mitigation of greenhouse effects. Pd has been extensively investigated as an electrocatalyst for the CO2 reduction to formate, which is an important raw material in the production of organic chemicals. However, the low selectivity and competitive reaction (hydrogen evolution reaction (HER)) have hindered the performance of monometallic Pd catalysts. In this paper, intermetallic PdBi nanosheets (NSs) are prepared for efficient CO2 reduction to formate. The highest Faradaic efficiency (FE) of formate on fully ordered PdBi NSs reaches 91.9% at -1.0 V vs. RHE, which outperforms that of the disordered PdBi and pure Pd catalysts. Density functional theory calculations suggest that compared to disordered PdBi NSs, the ordered structure can decrease the free energy barrier of *OCHO (a key intermediate of formate formation) and inhibit H2 evolution as well, thereby enhancing the activity and selectivity for formate production.

Special column on catalytic conversion of CO₂

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Metal organic framework-ionic liquid hybrid catalysts for the selective electrochemical reduction of CO2 to CH4 Ernest Pahuyo Delmo, Yian Wang, Jing Wang, Shangqian Zhu, Tiehuai Li, Xueping Qin, Yibo Tian, Qinglan Zhao, Juhee Jang, Yinuo Wang, Meng Gu, Lili Zhang, Minhua Shao 2022, 43 (7):  1687-1696.  DOI: 10.1016/S1872-2067(21)63970-0 Abstract ( 279 )   HTML ( 203 )   PDF (2299KB) ( 319 )   Supporting Information The electrochemical reduction of CO2 towards hydrocarbons is a promising technology that can utilize CO2 and prevent its atmospheric accumulation while simultaneously storing renewable energy. However, current CO2 electrolyzers remain impractical on a large scale due to the low current densities and faradaic efficiencies (FE) on various electrocatalysts. In this study, hybrid HKUST-1 metal-organic framework‒fluorinated imidazolium-based room temperature ionic liquid (RTIL) electrocatalysts are designed to selectively reduce CO2 to CH4. An impressive FE of 65.5% towards CH4 at -1.13 V is achieved for the HKUST-1/[BMIM][PF6] hybrid, with a stable FE greater than 50% maintained for at least 9 h in an H-cell. The observed improvements are attributed to the increased local CO2 concentration and the improved CO2-to-CH4 thermodynamics in the presence of the RTIL molecules adsorbed on the HKUST-1-derived Cu clusters. These findings offer a novel approach of immobilizing RTIL co-catalysts within porous frameworks for CO2 electroreduction applications.

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Synergetic effect of nitrogen-doped carbon catalysts for high-efficiency electrochemical CO2 reduction Chuhao Liu, Yue Wu, Jinjie Fang, Ke Yu, Hui Li, Wenjun He, Weng-Chon Cheong, Shoujie Liu, Zheng Chen, Jing Dong, Chen Chen 2022, 43 (7):  1697-1702.  DOI: 10.1016/S1872-2067(21)64006-8 Abstract ( 303 )   HTML ( 229 )   PDF (2977KB) ( 184 )   Supporting Information The use of carbon-based materials is an appealing strategy to solve the issue of excessive CO2 emissions. In particular, metal-free nitrogen-doped carbon materials (mf-NCs) have the advantages of convenient synthesis, cost-effectiveness, and high conductivity and are ideal electrocatalysts for the CO2 reduction reaction (CO2RR). However, the unclear identification of the active N sites and the low intrinsic activity of mf-NCs hinder the further development of high-performance CO2RR electrocatalysts. Achieving precise control over the synthesis of mf-NC catalysts with well-defined active N-species sites is still challenging. To this end, we adopted a facile synthesis method to construct a set of mf-NCs as robust catalysts for CO2RR. The resulting best-performing catalyst obtained a Faradaic efficiency of CO of approximately 90% at -0.55 V (vs. reversible hydrogen electrode) and good stability. The electrocatalytic performance and in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy measurements collectively revealed that graphitic and pyridinic N can synergistically adsorb CO2 and H2O and thus promote CO2 activation and protonation.

Special column on catalytic conversion of CO ₂

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Electroreduction of air-level CO2 with high conversion efficiency Yangshen Chen, Miao Kan, Shuai Yan, Junbo Zhang, Kunhao Liu, Yaqin Yan, Anxiang Guan, Ximeng Lv, Linping Qian, Gengfeng Zheng 2022, 43 (7):  1703-1709.  DOI: 10.1016/S1872-2067(21)63988-8 Abstract ( 362 )   HTML ( 265 )   PDF (2218KB) ( 300 )   Supporting Information The electrochemical conversion of carbon dioxide (CO2) has been attracting increasingly research interest in the past decade, with the ultimate goal of utilizing electricity from renewable energy to realize carbon neutrality, as well as economic and energy benefits. Nonetheless, the capture and concentrating of CO2 cost a substantial portion of energy, while almost all the reported researches showed CO2 electroreduction under high concentrations of (typically pure) CO2 reactants, and only very few recent studies have investigated the capability of applying low CO2 concentrations (such as ~10% in flue gases). In this work, we first demonstrated the electroreduction of 0.03% CO2 (in helium) in a homemade gas-phase electrochemical electrolyzer, using a low-cost copper (Cu) or nanoscale copper (nano-Cu) catalyst. Mixed with steam, the gas-phase CO2 was directly delivered onto the gas-solid interface with the Cu catalyst and reduced to CO, without the need/constraint of being adsorbed by aqueous solution or alkaline electrolytes. By tuning the catalyst and experimental parameters, the conversion efficiency of CO2 reached as high as ~95%. Furthermore, we demonstrated the direct electroreduction of 0.04% CO2 from real air sample with an optimized conversion efficiency of ~79%, suggesting a promising perspective of the electroreduction approach toward direct CO2 conversion.

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Highly dispersed nickel species on iron-based perovskite for CO2 electrolysis in solid oxide electrolysis cell Yingjie Zhou, Tianfu Liu, Yuefeng Song, Houfu Lv, Qingxue Liu, Na Ta, Xiaomin Zhang, Guoxiong Wang 2022, 43 (7):  1710-1718.  DOI: 10.1016/S1872-2067(21)63960-8 Abstract ( 272 )   HTML ( 282 )   PDF (3776KB) ( 234 )   Supporting Information Feasible construction of cathode materials with highly dispersed active sites can extend the triple-phase boundaries, and therefore leading to enhanced electrode kinetics for CO2 electrolysis in solid oxide electrolysis cell (SOEC). Herein, highly dispersed nickel species with low loading (1.0 wt%) were trapped within the La0.8Sr0.2FeO3-δ-Ce0.8Sm0.2O2-δ via a facial mechanical milling approach, which demonstrated excellent CO2 electrolysis performance. The highly dispersed nickel species can significantly alter the electronic structures of the LSF-SDC without affecting its porous network and facilitate oxygen vacancy formation, thus greatly promote the CO2 electrolysis performance. The highest current density of 1.53 A·cm-2 could be achieved when operated under 800 °C at 1.6 V, which is about 91% higher than the LSF-SDC counterpart.

Reviews

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Environmentally-friendly carbon nanomaterials for photocatalytic hydrogen production Sheng Xiong, Rongdi Tang, Daoxin Gong, Yaocheng Deng, Jiangfu Zheng, Ling Li, Zhanpeng Zhou, Lihua Yang, Long Su 2022, 43 (7):  1719-1748.  DOI: 10.1016/S1872-2067(21)63994-3 Abstract ( 312 )   HTML ( 305 )   PDF (27278KB) ( 354 )   Currently, the energy crisis is the crucial problem faced by the world, and photocatalytic hydrogen (H2) production is recognized with a chance to be a standout amongst those guaranteeing results to this issue. For a long time, photocatalytic H2 production has mainly relied on the noble metal catalysts. However, the limitations of noble metals themselves, such as scarcity and high cost, have severely restricted their large-scale application. Therefore, it is urgent to seek a cheaper, more efficient, and stable catalyst for photocatalytic H2 production. Fortunately, the emergence of carbon nanostructured materials (CNMs) has brought dawn. Its excellent structure and semiconductor performance can effectively participate in photocatalytic H2 production. CNMs have developed rapidly since they appeared in the field of photocatalytic water splitting. Therefore, it is necessary to summarize the latest progress of CNMs promptly for further development. This review introduced the CNMs, including carbon dots, fullerenes, carbon nanotubes, graphene, and graphdiyne, which is a powerful assistant in photocatalytic H2 production. CNMs can provide abundant adsorption and active sites, charge separation and transport channels, photocatalysts, co-catalysts and photosensitizers. Then, this review has introduced the strategy for enhancing CNMs in photocatalytic H2 production based on recent research. Finally, the challenge faced by CNMs in photocatalytic H2 production has prospected.

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Toward modular construction of cell-free multienzyme systems Yinchen Zhang, Ning Nie, Yifei Zhang 2022, 43 (7):  1749-1760.  DOI: 10.1016/S1872-2067(21)64002-0 Abstract ( 365 )   HTML ( 300 )   PDF (2615KB) ( 276 )   The implementation of multiple enzymes for chemical production in a cell-free scenario is an emerging field in biomanufacturing. It enables the redesign and reconstitution of new enzymatic routes for producing chemicals that may be hard to obtain from natural pathways. Although the construction of a cell-free multienzyme system is highly flexible and adaptable, it is challenging to make all enzymatic reactions act in concert. Recently, modular construction has been conceptualized as an effective way to harmonize diverse enzymatic reactions. In this review, we introduce the concept of a multienzyme module and exemplify representative modules found in Nature. We then categorize recent developments of synthetic multienzyme modules into main-reaction modules and auxiliary modules according to their roles in reaction routes. We highlight four main-reaction modules that can perform carbon metabolism, carbon assimilation, protein glycosylation and nonribosomal peptide synthesis, and exemplify auxiliary modules used for energy supply, protection and reinforcement for main reactions. The reactor-level modularization of multienzyme catalysis is also discussed.

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Photoelectrochemical nitrogen reduction: A step toward achieving sustainable ammonia synthesis Liqun Wang, Xiao Yan, Wenping Si, Daolan Liu, Xinggang Hou, Dejun Li, Feng Hou, Shi Xue Dou, Ji Liang 2022, 43 (7):  1761-1773.  DOI: 10.1016/S1872-2067(21)64001-9 Abstract ( 474 )   HTML ( 311 )   PDF (3888KB) ( 334 )   Industrial NH3 production mainly employs the well-known Haber-Bosch (H-B) process, which is associated with significant energy consumption and carbon emissions. Photoelectrochemical nitrogen reduction reaction (PEC-NRR) under ambient conditions is considered a promising alternative to the H-B process and has been attracting increasing attention owing to its associated energy efficiency and environmentally friendly characteristics. The performance of a PEC-NRR system, such as the NH3 yield, selectivity, and stability, is essentially determined by its key component, the photocathode. In this review, the latest progress in the development of photocathode materials employed in PEC-NRR is evaluated. The fundamental mechanisms and essential features required for the PEC-NRR are introduced, followed by a discussion of various types of photocathode materials, such as oxides, sulfides, selenides, black silicon, and black phosphorus. In particular, the PEC-NRR reaction mechanisms associated with these photocathode materials are reviewed in detail. Finally, the present challenges and future opportunities related to the further development of PEC-NRR are also discussed. This review aims to improve the understanding of PEC-NRR photocathode materials while also shedding light on the new concepts and significant innovations in this field.

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Photodeposition of earth-abundant cocatalysts in photocatalytic water splitting: Methods, functions, and mechanisms Hui Zhao, Qinyi Mao, Liang Jian, Yuming Dong, Yongfa Zhu 2022, 43 (7):  1774-1804.  DOI: 10.1016/S1872-2067(22)64105-6 Abstract ( 409 )   HTML ( 286 )   PDF (14117KB) ( 580 )   Photocatalytic water splitting based on semiconductor photocatalysts is a promising approach for producing carbon-neutral, sustainable, and clean H2 fuel. Cocatalyst loading, which is an appealing strategy, has been extensively employed to improve the photocatalytic efficiency semiconductors. In view of the high cost and rare preservation of noble metal cocatalysts that significantly hinder their utilization for large-scale energy production, various cocatalysts comprising earth-abundant elements have been developed as noble-metal-free candidates using different methods to boost photocatalytic water splitting. Among these preparation strategies, photodeposition has attracted tremendous attention in the deposition of earth-abundant cocatalysts owing to its simplicity and moderate availability, improved interfacial charge separation and transfer, and abundant active sites on the surface. In this review, we first summarize the deposition principles, deposition advantages, categories of cocatalysts, roles of cocatalysts, influencing factors, modification strategies, and design considerations in the photodeposition of earth-abundant cocatalysts. The photodeposited earth-abundant cocatalysts for the photocatalytic H2 evolution half reaction, photocatalytic O2 evolution half reaction, and overall photocatalytic water splitting are discussed. Finally, some perspectives on the challenges and possible future directions for the photodeposition of earth-abundant cocatalysts in photocatalytic water splitting are presented.

Communications

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Aromatic bromination with hydrogen production on organic-inorganic hybrid perovskite-based photocatalysts under visible light irradiation Yanfei Zhang, Hong Wang, Yan Liu, Can Li 2022, 43 (7):  1805-1811.  DOI: 10.1016/S1872-2067(22)64101-9 Abstract ( 230 )   HTML ( 266 )   PDF (1105KB) ( 241 )   Supporting Information Aromatic bromides are important chemicals in nature and chemical industries. However, their traditional synthesis routes suffer from low atomic economy and pollutant formation. Herein, we show that organic-inorganic hybrid perovskite methylammonium lead bromide (MAPbBr3) nanocrystals stabilized in aqueous HBr solution can achieve simultaneous aromatic bromination and hydrogen evolution using HBr as the bromine source under visible light irradiation. By hybridizing MAPbBr3 with Pt/Ta2O5 and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as electron- and hole-transporting motifs, aromatic bromides were achieved from aromatic compounds with high yield (up to 99%) and selectivity (up to 99%) with the addition of N,N-dimethylformamide or its analogs. The mechanistic studies revealed that the bromination proceeds via an electrophilic attack pathway and that HOBr may be the key intermediate in the bromination reaction.

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The synthesis of tetracyclic coumarins via decarboxylative asymmetric [4+2] cycloadditions enabled by Pd(0)/Cu(I) synergistic catalysis Kai Wang, Xiangfeng Lin, Qian Li, Yan Liu, Can Li 2022, 43 (7):  1812-1817.  DOI: 10.1016/S1872-2067(21)64051-2 Abstract ( 156 )   HTML ( 257 )   PDF (1036KB) ( 206 )   Supporting Information Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacological activities. However, a direct stereoselective method from simple and readily-made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles. Herein, we develop a decarboxylative asymmetric [4+2] cycloaddition of 3-cyanocoumarins with vinyl benzoxazinones, affording the coumarin-derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities (>20/1 d.r.) and enantioselectivities (up to 99% ee). This direct enantioselective reaction was achieved by a Pd(0)/Cu(I) bimetallic catalytic system. The mechanism studies indicated that the synergistic activation effect, in which chiral Cu(I) as an available Lewis acid catalyst activates 3-cyanocoumarin and chiral Pd(0) complex activates benzoxazinone by the formation of π-allyl-palladium intermediate, plays an important role on the stereoselective control. The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetallic catalytic system.

Articles

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Energy funneling and charge separation in CdS modified with dual cocatalysts for enhanced H2 generation Meiyu Zhang, Chaochao Qin, Wanjun Sun, Congzhao Dong, Jun Zhong, Kaifeng Wu, Yong Ding 2022, 43 (7):  1818-1829.  DOI: 10.1016/S1872-2067(21)64009-3 Abstract ( 150 )   HTML ( 286 )   PDF (8447KB) ( 140 )   Supporting Information Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis. However, the effect of molecular cocatalysts on energy funneling (i.e., directional energy transfer) inside semiconductor photocatalysts has not been demonstrated yet. Here we prepared CdS nanorods with both thin and thick rods and anchored the conjugated molecules 2-mercaptobenzimidazole (MBI) and cobalt molecular catalysts (MCoA) sequentially onto the surface of nanorods. Transient absorption measurements revealed that MBI molecules facilitated energy funneling from thin to thick rods by the electronic coupling between thin and thick nanorods, which is essentially a light-harvesting antenna approach to enhance the charge generation efficiency in the reaction center (here the thick rods). Moreover, MBI and MCoA molecules selectively extracted photogenerated holes and electrons of CdS nanorods rapidly, leading to efficient charge separation. Consequently, CdS/MBI/MCoA displayed 15 times enhanced photocatalytic H2 evolution (1.65 mL) than pure CdS (0.11 mL) over 3 h of illumination. The amount of H2 evolution reached 60 mL over 48 h of illumination with a high turnover number of 26294 and an apparent quantum efficiency of 71% at 420 nm. This study demonstrates a novel design principle for next-generation photocatalysts.

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Non-noble metal single-atom catalyst with MXene support: Fe1/Ti2CO2 for CO oxidation Chun Zhu, Jin-Xia Liang, Yang-Gang Wang, Jun Li 2022, 43 (7):  1830-1841.  DOI: 10.1016/S1872-2067(21)64027-5 Abstract ( 304 )   HTML ( 227 )   PDF (6843KB) ( 295 )   Supporting Information MXenes have attracted considerable attention owing to their versatile and excellent physicochemical properties. Especially, they have potential applications as robust support for single atom catalysts. Here, quantum chemical studies with density functional theory are carried out to systematically investigate the geometries, stability, electronic properties of oxygen functionalized Ti2C (Ti2CO2) supported single-atom catalysts M1/Ti2CO2 (M = Fe, Co, Ni, Cu Ru, Rh, Pd, Ag Os, Ir, Pt, Au). A new non-noble metal SAC Fe1/Ti2CO2 has been found to show excellent catalytic performance for low-temperature CO oxidation after screening the group 8-11 transition metals. We find that O2 and CO adsorption on Fe1 atom of Fe1/Ti2CO2 is favorable. Accordingly, five possible mechanisms for CO oxidation on this catalyst are evaluated, including Eley-Rideal, Langmuir-Hinshelwood, Mars-van Krevelen, Termolecular Eley-Rideal, and Termolecular Langmuir-Hinshelwood (TLH) mechanisms. Based on the calculated reaction energies for different pathways, Fe1/Ti2CO2 shows excellent kinetics for CO oxidation via TLH mechanism, with distinct low-energy barrier (0.20 eV) for the rate-determining step. These results demonstrate that Fe1/Ti2CO2 MXene is highly promising 2D materials for building robust non-noble metal catalysts.

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Ultrathin 3D radial tandem-junction photocathode with a high onset potential of 1.15 V for solar hydrogen production Shaobo Zhang, Huiting Huang, Zhijie Zhang, Jianyong Feng, Zongguang Liu, Junzhuan Wang, Jun Xu, Zhaosheng Li, Linwei Yu, Kunji Chen, Zhigang Zou 2022, 43 (7):  1842-1850.  DOI: 10.1016/S1872-2067(21)64046-9 Abstract ( 163 )   HTML ( 233 )   PDF (9769KB) ( 145 )   Supporting Information Combining a progressive tandem junction design with a unique Si nanowire (SiNW) framework paves the way for the development of high-onset-potential photocathodes and enhancement of solar hydrogen production. Herein, a radial tandem junction (RTJ) thin film water-splitting photocathode has been demonstrated experimentally for the first time. The photocathode is directly fabricated on vapor-liquid-solid-grown SiNWs and consists of two radially stacked p-i-n junctions, featuring hydrogenated amorphous silicon (a-Si:H) as the outer absorber layer, which absorbs short wavelengths, and hydrogenated amorphous silicon germanium (a-SiGe:H) as the inner layer, which absorbs long wavelengths. The randomly distributed SiNW framework enables highly efficient light-trapping, which facilitates the use of very thin absorber layers of a-Si:H (~50 nm) and a-SiGe:H (~40 nm). In a neutral electrolyte (pH = 7), the three-dimensional (3D) RTJ photocathode delivers a high photocurrent onset of 1.15 V vs. the reversible hydrogen electrode (RHE), accompanied by a photocurrent of 2.98 mA/cm2 at 0 V vs. RHE, and an overall applied-bias photon-to-current efficiency of 1.72%. These results emphasize the promising role of 3D radial tandem technology in developing a new generation of durable, low-cost, high-onset-potential photocathodes capable of large-scale implementation.

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Photocatalytic selective oxidation of aromatic alcohols coupled with hydrogen evolution over CdS/WO3 composites Yu-Lan Wu, Ming-Yu Qi, Chang-Long Tan, Zi-Rong Tang, Yi-Jun Xu 2022, 43 (7):  1851-1859.  DOI: 10.1016/S1872-2067(21)63989-X Abstract ( 172 )   HTML ( 246 )   PDF (7382KB) ( 522 )   Supporting Information Simultaneously utilizing photogenerated electrons and holes to convert renewable biomass and its derivatives into corresponding value-added products and hydrogen (H2) is a promising strategy to deal with the energy and environmental crisis. Herein, we report a facile hydrothermal method to construct a direct Z-scheme CdS/WO3 binary composite for photocatalytic coupling redox reaction, simultaneously producing H2 and selectively converting aromatic alcohols into aromatic aldehydes in one pot. Compared with bare CdS and WO3, the CdS/WO3 binary composite exhibits significantly enhanced performance for this photocatalytic coupled redox reaction, which is ascribed to the extended light harvesting range, efficient charge carrier separation rate and optimized redox capability of CdS/WO3 composite. Furthermore, the feasibility of converting various aromatic alcohols to corresponding aldehydes coupled with H2 evolution on the CdS/WO3 photocatalyst is proved and a reasonable reaction mechanism is proposed. It is hoped that this work can provide a new insight into the construction of direct Z-scheme photocatalysts to effectively utilize the photogenerated electrons and holes for photocatalytic coupled redox reaction.

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Computational screening of O-functional MXenes for electrocatalytic ammonia synthesis Yijing Gao, Shijie Zhang, Xiang Sun, Wei Zhao, Han Zhuo, Guilin Zhuang, Shibin Wang, Zihao Yao, Shengwei Deng, Xing Zhong, Zhongzhe Wei, Jian-guo Wang 2022, 43 (7):  1860-1869.  DOI: 10.1016/S1872-2067(21)64011-1 Abstract ( 171 )   HTML ( 200 )   PDF (4001KB) ( 268 )   Supporting Information The nitrogen reduction reaction (NRR) using new and efficient electrocatalysts is a promising alternative to the traditional Haber-Bosch process. Nevertheless, it remains a challenge to design efficient catalysts with improved catalytic performance. Herein, various O-functional MXenes were investigated as NRR catalysts by a combination of density functional theory calculations and least absolute shrinkage and selection operator (LASSO) regression. Nb3C2OX has been regarded as a promising catalyst for the NRR because of its stability, activity, and selectivity. The potential-determining step is *NH2 hydrogenation to *NH3 with a limiting potential of -0.45 V. Furthermore, via LASSO regression, the descriptors and equations fitting the relationship between the properties of O-functional MXenes and NRR activity have been proposed. This work not only provides a rational design strategy for catalysts but also provides machine learning data for further investigation.

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Synergy of staggered stacking confinement and microporous defect fixation for high-density atomic FeII-N4 oxygen reduction active sites Menghui Chen, Yongting Chen, Zhili Yang, Jin Luo, Jialin Cai, Joey Chung-Yen Jung, Jiujun Zhang, Shengli Chen, Shiming Zhang 2022, 43 (7):  1870-1878.  DOI: 10.1016/S1872-2067(21)63992-X Abstract ( 118 )   HTML ( 238 )   PDF (2930KB) ( 154 )   Supporting Information The development of high-performance nonprecious metal catalysts (NPMCs) to supersede Pt-based catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells is highly desirable but remains challenging. In this paper, we present a pyrolysis strategy for spatial confinement and active-site fixation using iron phthalocyanine (FePc), phthalocyanine (Pc) and Zn salts as precursors. In the obtained carbon-based NPMC with a hierarchically porous nanostructure of thin-layered carbon nanosheets, nearly 100% of the total Fe species are FeII-N4 active sites. In contrast, pyrolyzing FePc alone forms Fe-based nanoparticles embedded in amorphous carbon with only 5.9% FeII-N4 active sites. Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggered π-π stacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe-based nanoparticles via aggregation. Furthermore, Zn-induced microporous defects allow the fixation of FeII-N4 active sites. The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic FeII-N4 active sites that can enhance the ORR. The optimal FeII-N4-C electrocatalyst outperforms a commercial Pt/C catalyst in terms of half-wave potential, methanol tolerance, and long-term stability in alkaline media. This modulation strategy can greatly advance efforts to develop high-performance NPMCs.

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An integrated approach to the key parameters in methanol-to-olefins reaction catalyzed by MFI/MEL zeolite materials Chuncheng Liu, Evgeny A. Uslamin, Sophie H. van Vreeswijk, Irina Yarulina, Swapna Ganapathy, Bert M. Weckhuysen, Freek Kapteijn, Evgeny A. Pidko 2022, 43 (7):  1879-1893.  DOI: 10.1016/S1872-2067(21)63990-6 Abstract ( 258 )   HTML ( 237 )   PDF (4970KB) ( 242 )   Identification of the catalyst characteristics correlating with the key performance parameters including selectivity and stability is key to the rational catalyst design. Herein we focused on the identification of property-performance relationships in the methanol-to-olefin (MTO) process by studying in detail the catalytic behaviour of MFI, MEL and their respective intergrowth zeolites. The detailed material characterization reveals that both the high production of propylene and butylenes and the large MeOH conversion capacity correlate with the enrichment of lattice Al sites in the channels of the pentasil structure as identified by 27Al MAS NMR and 3-methylpentane cracking results. The lack of correlation between MTO performance and other catalyst characteristics, such as crystal size, presence of external Brønsted acid sites and Al pairing suggests their less pronounced role in defining the propylene selectivity. Our analysis reveals that catalyst deactivation is rather complex and is strongly affected by the enrichment of lattice Al in the intersections, the overall Al-content, and crystal size. The intergrowth of MFI and MEL phases accelerates the catalyst deactivation rate.

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Unveiling the highly disordered NbO6 units as electron-transfer sites in Nb2O5 photocatalysis with N-hydroxyphthalimide under visible light irradiation Kaiyi Su, Chaofeng Zhang, Yehong Wang, Jian Zhang, Qiang Guo, Zhuyan Gao, Feng Wang 2022, 43 (7):  1894-1905.  DOI: 10.1016/S1872-2067(21)64026-3 Abstract ( 416 )   HTML ( 218 )   PDF (2656KB) ( 219 )   Supporting Information Although different NbOx units are present in Nb2O5-based catalysts, the correlations between these structures and activity remain unclear, which considerably hinders the further development of Nb2O5 photocatalysis. Herein, we utilized N-hydroxyphthalimide (NHPI) as the probe molecule to distinguish the role of different NbOx units in the activation of C-H bond under visible light irradiation. With the addition of NHPI, Nb2O5 catalysts with highly disordered NbO6 units exhibited higher activities than that with slightly disordered NbO6 units (419‒495 vs. 82 μmol·g-1·h-1) in photocatalytic selective oxidation of ethylbenzene. Revealed by Raman spectra, electron paramagnetic resonance spectra, and transmission-electron-microscopy images, highly disordered NbO6 units were confirmed to act as the active sites for the transfer of photogenerated electrons from NHPI, promoting the generation of phthalimide-N-oxyl (PINO) radicals for the enhanced conversion of ethylbenzene under visible light irradiation. This study provides guidance on the role of local NbOx units in Nb2O5 photocatalysis.

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Charge transfer and orbital reconstruction of non-noble transition metal single-atoms anchored on Ti2CTx-MXenes for highly selective CO2 electrochemical reduction Neng Li, Jiahe Peng, Zuhao Shi, Peng Zhang, Xin Li 2022, 43 (7):  1906-1917.  DOI: 10.1016/S1872-2067(21)64018-4 Abstract ( 193 )   HTML ( 260 )   PDF (6103KB) ( 390 )   Supporting Information Inspired by MXene nanosheets and their regulation of surface functional groups, a series of Ti2C-based single-atom electrocatalysts (TM@Ti2CTx, TM = V, Cr, Mn, Fe, Co, and Ni) with two different functional groups (T = -O and -S) was designed. The CO2RR catalytic performance was studied using well-defined ab initio calculations. Our results show that the CO2 molecule can be more readily activated on TM @Ti2CO2 than the TM@Ti2CS2 surface. Bader charge analysis reveals that the Ti2CO2 substrate is involved in the adsorption reaction, and enough electrons are injected into the 2π*u orbital of CO2, leading to a V-shaped CO2 molecular configuration and partial negative charge distribution. The V-shaped CO2 further reduces the difficulty of the first hydrogenation reaction step. The calculated ΔG of the first hydrogenation reaction on TM@Ti2CO2 was significantly lower than that of the TM@Ti2CS2 counterpart. However, the subsequent CO2 reduction pathways show that the UL of the potential determining step on TM@Ti2CS2 is smaller than that of TM@Ti2CO2. Combining the advantages of both TM@Ti2CS2 and TM@Ti2CO2, we designed a mixed functional group surface with -O and -S to anchor TM atoms. The results show that Cr atoms anchored on the surface of mixed functional groups exhibit high catalytic activity for the selective production of CH4. This study opens an exciting new avenue for the rational design of highly selective MXene-based single-atom CO2RR electrocatalysts.

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Revealing the concentration of hydrogen peroxide in fuel cell catalyst layers by an in-operando approach Chun-Yu Qiu, Li-yang Wan, Yu-Cheng Wang, Muhammad Rauf, Yu-Hao Hong, Jia-yin Yuan, Zhi-You Zhou, Shi-Gang Sun 2022, 43 (7):  1918-1926.  DOI: 10.1016/S1872-2067(21)63993-1 Abstract ( 253 )   HTML ( 302 )   PDF (3603KB) ( 123 )   Supporting Information To evaluate the H2O2-tolerance of non-Pt oxygen reduction reaction (ORR) catalysts as well as investigate the H2O2-induced decay mechanism, the selection of an appropriate H2O2 concentration is a prerequisite. However, the concentration criterion is still unclear because of the lack of in-operando methods to determine the actual concentration of H2O2 in fuel cell catalyst layers. In this work, an electrochemical probe method was successfully established to in-operando monitor the H2O2 in non-Pt catalyst layers for the first time. The local concentration of H2O2 was revealed to reach 17 mmol/L, which is one order of magnitude higher than that under aqueous electrodes test conditions. Powered by the new knowledge, a concentration criterion of at least 17 mmol/L is suggested. This work fills in the large gap between aqueous electrode tests and the real fuel cell working conditions, and highlights the importance of in-operando monitoring methods.

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Ultradurable fluorinated V2AlC for peroxymonosulfate activation in organic pollutant degradation processes Chao Li, Chenjie Song, Hui Li, Liqun Ye, Yixue Xu, Yingping Huang, Gongzhe Nie, Rumeng Zhang, Wei Liu, Niu Huang, Po Keung Wong, Tianyi Ma 2022, 43 (7):  1927-1936.  DOI: 10.1016/S1872-2067(21)64050-0 Abstract ( 113 )   HTML ( 237 )   PDF (6707KB) ( 146 )   Supporting Information Vanadium-based catalysts are considered the most promising materials to replace cobalt-based catalysts for the activation of peroxymonosulfate (PMS) to degrade organic pollutants. However, these traditional vanadium species easily leak out metal ions that can affect the environment, even though the of vanadium is much less than that of cobalt. Compared to other vanadium-based catalysts, e.g., V2O3, fluorinated V2AlC shows a high and constant activity and reusability regarding PMS activation. Furthermore, it features extremely low ion leakage. Active oxygen species scavenging and electron spin resonance measurements reveal that the main reactive oxygen species was 1O2, which was induced by a two-dimensional confinement effect. More importantly, for the real-life application of tetracycline (TC) degradation, the introduction of fluorine changed the adsorption mode of TC over the catalyst, thereby changing the degradation path. The intermediate products were detected by liquid-chromatography mass spectroscopy (LC-MS), and a possible degradation path was proposed. The environmental impact test of the decomposition products showed that the toxicity of the degradation intermediates was greatly reduced. Therefore, the investigated ultradurable catalyst material provides a basis for the practical application of advanced PMS oxidation technology.

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Heterostructuring 2D TiO2 nanosheets in situ grown on Ti3C2Tx MXene to improve the electrocatalytic nitrogen reduction Xiu Qian, Yanjiao Wei, Mengjie Sun, Ye Han, Xiaoli Zhang, Jian Tian, Minhua Shao 2022, 43 (7):  1937-1944.  DOI: 10.1016/S1872-2067(21)64020-2 Abstract ( 318 )   HTML ( 267 )   PDF (3775KB) ( 240 )   Supporting Information In this study, TiO2 nanosheets (NSs) grown in situ on extremely conductive Ti3C2Tx MXene to form TiO2/Ti3C2Tx MXene composites with abundant active sites are proposed to effectively achieve electrocatalytic NH3 synthesis. Electron transfer can be promoted by Ti3C2Tx MXene with high conductivity. Meanwhile, the TiO2 NSs in-situ formation can not only avoid Ti3C2Tx MXene microstacking but also enhance the surface specific area of Ti3C2Tx MXene. The TiO2/Ti3C2Tx MXene catalyst reaches a high Faradaic efficiency (FE) of 44.68% at -0.75 V vs. RHE and a large NH3 yield of 44.17 µg h-1 mg-1cat. at -0.95 V, with strong electrochemical durability. 15N isotopic labeling experiments imply that the N in the produced NH3 originated from the N2 of the electrolyte. DFT calculations were conducted to determine the possible NRR reaction pathways for TiO2/Ti3C2Tx MXene composites. MXene catalysts combined with other materials have been rationally designed for efficient ammonia production under ambient conditions.

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Synthesis of mesoporous high-silica zeolite Y and their catalytic cracking performance Wenhao Cui, Dali Zhu, Juan Tan, Nan Chen, Dong Fan, Juan Wang, Jingfeng Han, Linying Wang, Peng Tian, Zhongmin Liu 2022, 43 (7):  1945-1954.  DOI: 10.1016/S1872-2067(21)64043-3 Abstract ( 238 )   HTML ( 265 )   PDF (3160KB) ( 215 )   Supporting Information Mesoporous high-silica zeolite Y with advantages of improved accessibility of acid sites and mass transport properties is highly desired catalytic materials for oil refinery, fine chemistry and emerging biorefinery. Here, we report the direct synthesis of mesoporous high-silica zeolite Y (named MSY, SiO2/Al2O3 ≥ 9.8) and their excellent catalytic cracking performance. The obtained MSY materials are mesoporous single crystals with octahedral morphology, abundant mesoporosity and excellent (hydro)thermal stability. Both the acid concentration and acid strength of H-form MSY are obviously higher than those of commercial ultra-stable Y (USY), which should be attributed to the uniform Al distribution of MSY zeolite. The H-MSY displays an obviously reduced deactivation rate and improved catalytic activity in the cracking reaction of bulky 1,3,5-triisopropylbenzene (TIPB), as compared with its mesoporogen-free counterpart and USY. In addition, H-MSY was investigated as catalyst for the cracking of industrial heavy oil. The MSY-based catalyst (after aging at 800 oC in 100% steam for 17 h) exhibits superior conversion (7.64% increase) and gasoline yield (16.37% increase) than industrial fluid catalytic cracking (FCC) catalyst under the investigated conditions.

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Ammonium cobalt phosphate with asymmetric coordination sites for enhanced electrocatalytic water oxidation Jing Qi, Mingxing Chen, Wei Zhang, Rui Cao 2022, 43 (7):  1955-1962.  DOI: 10.1016/S1872-2067(21)64035-4 Abstract ( 229 )   HTML ( 690 )   PDF (2337KB) ( 169 )   Supporting Information Cobalt-based materials have been considered as promising candidates to electrocatalyze water oxidation. However, the structure-performance correlation remains largely elusive, due to the complex material structures and diverse performance-influencing factors in those Co-based catalysts. In this work, we designed two cobalt phosphates with distinct Co symmetry to explore the effect of coordination symmetry on electrocatalytic water oxidation. The two analogues have similar morphology, Co valence and 6-coordinated Co octahedron, but with different coordination symmetry. In contrast to symmetric Co3(PO4)2·8H2O, asymmetric NH4CoPO4·H2O exhibited enhanced electrocatalytic water oxidation activity in a neutral aqueous solution. It is proven that, by experimental and theoretical studies, the asymmetric Co coordination sites can facilitate the surface reconstruction under anodic polarization to boost the electrocatalysis. Based on this contrastive platform with distinct symmetry differences, the preferred configuration in cobalt-oxygen octahedrons for water oxidation has been straightforwardly assigned.