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Chinese Journal of Catalysis
2024, Vol. 65
Online: 18 October 2024

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Cover: Jun Xu and co-workers have successfully synthesized a visible-light-responsive SrTaO2N:Mg photocatalyst through a one-pot Mg doping strategy, utilizing the KCl molten salt-assisted thermal nitridation method. The Mg doping has an effect on crystal growth, particle size, band gap position, defect suppression, charge separation and transfer. Notably, SrTaO2N:Mg loaded with cocatalyst exhibits photocatalytic H2 evolution with 10 times that of SrTaO2N undoped with Mg. Furthermore, by coupling this photocatalyst with Au-FeCoOx modified BiVO4 as an O2-evolution photocatalyst, and employing [Fe(CN)6]3?/[Fe(CN)6]4? as the redox shuttle, an enhanced Z-scheme overall water splitting system is achieved. This accomplishment provides an important reference for the design of efficient photocatalytic overall water splitting systems. Read more about the article behind the cover on page 70–78.

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Dual-channel redox reactions for photocatalytic H2-evolution coupled with photoreforming oxidation of waste materials Huan Liu, Shaoxiong He, Jiafu Qu, Yahui Cai, Xiaogang Yang, Chang Ming Li, Jundie Hu 2024, 65:  1-39.  DOI: 10.1016/S1872-2067(24)60118-X Abstract ( 86 )   HTML ( 29 )   PDF (36945KB) ( 66 )   Dual-channel redox reaction system is advantageous for photocatalytic hydrogen (H2) production when coupled with photoreforming oxidation of waste materials, benefiting both thermodynamically and kinetically. However, existing reviews primarily focus on specific oxidation reactions, such as oxidative organic synthesis and water remediation, often neglecting recent advancements in plastic upgrading, biomass conversion, and H2O2 production, and failing to provide an in-depth discussion of catalytic mechanisms. This review addresses these gaps by offering a comprehensive overview of recent advancements in dual-channel redox reactions for photocatalytic H2-evolution and waste photoreforming. It highlights waste-to-wealth design concepts, examines the challenges, advantages and diverse applications of dual-channel photocatalytic reactions, including photoreforming of biomass, alcohol, amine, plastic waste, organic pollutants, and H2O2 production. Emphasizing improvement strategies and exploration of catalytic mechanisms, it includes advanced in-situ characterization, spin capture experiments, and DFT calculations. By identifying challenges and future directions in this field, this review provides valuable insights for designing innovative dual-channel photocatalytic systems.

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CO2-assisted oxidation dehydrogenation of light alkanes over metal-based heterogeneous catalysts Yingbin Zheng, Xinbao Zhang, Junjie Li, Jie An, Longya Xu, Xiujie Li, Xiangxue Zhu 2024, 65:  40-69.  DOI: 10.1016/S1872-2067(24)60094-X Abstract ( 564 )   HTML ( 22 )   PDF (6562KB) ( 299 )   Light olefins are important platform feedstocks in the petrochemical industry, and the ongoing global economic development has driven sustained growth in demand for these compounds. The dehydrogenation of alkanes, derived from shale gas, serves as an alternative olefins production route. Concurrently, the target of realizing carbon neutrality promotes the comprehensive utilization of greenhouse gas. The integrated process of light alkanes dehydrogenation and carbon dioxide reduction (CO2-ODH) can produce light olefins and realize resource utilization of CO2, which has gained wide popularity. With the introduction of CO2, coke deposition and metal reduction encountered in alkanes dehydrogenation reactions can be effectively suppressed. CO2-assisted alkanes dehydrogenation can also reduce the risk of potential explosion hazard associated with O2-oxidative dehydrogenation reactions. Recent investigations into various metal-based catalysts including mono- and bi-metallic alloys and oxides have displayed promising performances due to their unique properties. This paper provides the comprehensive review and critical analysis of advancements in the CO2-assisted oxidative dehydrogenation of light alkanes (C2-C4) on metal-based catalysts developed in recent years. Moreover, it offers a comparative summary of the structural properties, catalytic activities, and reaction mechanisms over various active sites, providing valuable insights for the future design of dehydrogenation catalysts.

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Mg-doped SrTaO2N as a visible-light-driven H2-evolution photocatalyst for accelerated Z-scheme overall water splitting Jun Xu, Ying Luo, Qiaoqi Guo, Wenzheng Sun, Shanshan Chen, Zheng Wang, Hong He 2024, 65:  70-78.  DOI: 10.1016/S1872-2067(24)60082-3 Abstract ( 97 )   HTML ( 13 )   PDF (3430KB) ( 65 )   Supporting Information Perovskite SrTaO2N is one of the most promising narrow-bandgap photocatalysts for Z-scheme overall water splitting. However, the formation of defect states during thermal nitridation severely hinders the separation of charges, resulting in poor photocatalytic activity. In the present study, we successfully synthesize SrTaO2N photocatalyst with low density of defect states, uniform morphology and particle size by flux-assisted one-pot nitridation combined with Mg doping. Some important parameters, such as the size of unit cell, the content of nitrogen, and microstructure, prove the successful doping of Mg. The defect-related carrier recombination has been significantly reduced by Mg doping, which effectively promotes the charge separation. Moreover, Mg doping induces a change of the band edge, which makes proton reduction have a stronger driving force. After modifying with the core/shell-structured Pt/Cr2O3 cocatalyst, the H2 evolution activity of the optimized SrTaO2N:Mg is 10 times that of the undoped SrTaO2N, with an impressive apparent quantum yield of 1.51% at 420 nm. By coupling with Au-FeCoOx modified BiVO4 as an O2-evolution photocatalyst and [Fe(CN)6]3−/[Fe(CN)6]4− as the redox couple, a redox-based Z-scheme overall water splitting system is successfully constructed with an apparent quantum yield of 1.36% at 420 nm. This work provides an alternative way to prepare oxynitride semiconductors with reduced defects to promote the conversion of solar energy.

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Understanding the roles of Brønsted/Lewis acid sites on manganese oxide-zeolite hybrid catalysts for low-temperature NH3-SCR Hyun Sub Kim, Hwangho Lee, Hongbeom Park, Inhak Song, Do Heui Kim 2024, 65:  79-88.  DOI: 10.1016/S1872-2067(24)60112-9 Abstract ( 59 )   HTML ( 9 )   PDF (16606KB) ( 36 )   Supporting Information Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NOx removal reactions through the inter-particle diffusion of intermediate species, their subsequent reaction mechanism on acid sites is still unclear and requires investigation. In this study, the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions, which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species. Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NOx with NH3 (NH3-SCR) reaction demonstrate that the Lewis acid sites over MnOx are more active for NO reduction but have lower selectivity to N2 than Brønsted acids sites. Brønsted acid sites primarily produce N2, whereas Lewis acid sites primarily produce N2O, contributing to unfavorable N2 selectivity. The Brønsted acid sites present in Y zeolite, which are stronger than those on MnOx, accelerate the NH3-SCR reaction in which the nitrite/nitrate species diffused from the MnOx particles rapidly convert into the N2. Therefore, it is important to design the catalyst so that the activated NO species formed in MnOx diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnOx particle. For the physically mixed H-MnOx+H-Y sample, the abundant Brønsted/Lewis acid sites in H-MnOx give rise to significant consumption of activated NO species before their inter-particle diffusion, thereby hindering the enhancement of the synergistic effects. Furthermore, we found that the intercalated K+ in K-MnOx has an unexpected favorable role in the NO reduction rate, probably owing to faster diffusion of the activated NO species on K-MnOx than H-MnOx. This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.

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Promoting role of Ru species on Ir-Fe/BN catalyst in 1,2-diols hydrogenolysis to secondary alcohols Ben Liu, Yoshinao Nakagawa, Mizuho Yabushita, Keiichi Tomishige 2024, 65:  89-102.  DOI: 10.1016/S1872-2067(24)60110-5 Abstract ( 94 )   HTML ( 6 )   PDF (4471KB) ( 44 )   Supporting Information Noble metal-based-bimetallic catalysts have been highly investigated and applied in wide applications including biomass transformation via regioselective C−O hydrogenolysis while further modification especially with noble metal is highly promising yet still under investigation. Herein, Ru was found as an effective modifier among the screened noble metals (Ru, Pt, Rh, Pd, Au, and Ag) for Ir-Fe/BN (Ir = 5 wt%, Fe/Ir = 0.25) catalyst in terminal C−O hydrogenolysis of 1,2-butanediol (1,2-BuD) to 2-butanol (2-BuOH). Only trace amount of Ru (up to 0.5 wt%) was effective in terms of high 2-BuOH selectivity (> 60%) and activity (about twice). Larger amount of Ru species (3 wt%) highly enhanced the activity but gave low selectivity to 2-BuOH with by-products of terminal C−C bond scission. Optimized catalyst (Ru(0.5)-Ir-Fe/BN) was reusable at least 4 times and gave moderate 2-BuOH yield (47%) in hydrogenolysis of 1,2-BuD. The promoting effect of Ru addition (0.5 wt%) to Ir-Fe/BN on hydrogenolysis of various alcohols was also confirmed. Combining catalytic tests with various characterizations, the promotion mechanism of Ru species in trimetallic catalysts was clarified. The Ru species in Ru(0.5)-Ir-Fe/BN form alloy with Ir and are enriched at the interface with BN surface, and direct interaction between Ru and Fe was not necessary in Ru-Ir-Fe alloy. The interface of Ir and Fe on the surface of Ir-Fe alloy may work as active sites for 1,2-diols to secondary alcohols via direct C−O hydrogenolysis, in which Ru-modified Ir activates H2 to form hydride-like species. The activity of Ru species in C−C bond cleavage was highly suppressed due to the direct interaction with Ir species and less exposed to substrate. Larger loading amount of Ru species (3 wt%) led to the formation Ru-rich trimetallic alloy, which further works as active sites for C−C bond scission.

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Dipole polarization modulating of vinylene-linked covalent organic frameworks for efficient photocatalytic hydrogen evolution Ming Wang, Yaling Li, Dengxin Yan, Hui Hu, Yujie Song, Xiaofang Su, Jiamin Sun, Songtao Xiao, Yanan Gao 2024, 65:  103-112.  DOI: 10.1016/S1872-2067(24)60113-0 Abstract ( 143 )   HTML ( 10 )   PDF (4498KB) ( 57 )   Supporting Information Photocatalytic hydrogen (H2) evolution using covalent organic frameworks (COFs) is an attractive and promising avenue for exploration, but one of its big challenges is low photo-induced charge separation. In this study, we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency, achieved through atomic modulation (O, S, and Se) of the COF monomer. Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment, thereby affecting charge separation efficiency and photostability, which in turn affects the rates of photocatalytic H2 evolution. As a result, the newly developed TMT-BO-COF, which contains highly electronegative O atoms, exhibits the lowest exciton binding energy, the highest efficiency in charge separation and transportation, and the longest lifetime of the active charges. This leads to an impressive average H2 production rate of 23.7 mmol g-1 h-1, which is 2.5 and 24.5 times higher than that of TMT-BS-COF (containing S atoms) and TMT-BSe-COF (containing Se atoms), respectively. A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations. Our findings provide new insights into the design of highly photoactive organic framework materials for H2 evolution and beyond.

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Atomic orbitals modulated dual functional bimetallic phosphides derived from MOF on MOF structure for boosting high efficient overall water splitting Bohan An, Weilong Liu, Jipeng Dong, Ning Li, Yangqin Gao, Lei Ge 2024, 65:  113-125.  DOI: 10.1016/S1872-2067(24)60124-5 Abstract ( 86 )   HTML ( 6 )   PDF (6384KB) ( 49 )   Supporting Information The electronic modulation characteristics of efficient metal phosphide electrocatalysts can be utilized to tune the performance of oxygen evolution reaction (OER). However, improving the overall water splitting performance remains a challenging task. By building metal organic framework (MOF) on MOF heterostructures, an efficient strategy for controlling the electrical structure of MOFs was presented in this study. ZIF-67 was in-situ synthesized on MIL-88 (Fe) using a two-step self-assembly method, followed by low-temperature phosphorization to ultimately synthesize FeP-CoP3 bimetallic phosphides. By combining atomic orbital theory and theoretical calculations (density functional theory), the results reveal the successful modulation of electronic orbitals in FeP-CoP3 bimetallic phosphides, which are synthesized from MOF on MOF structure. The synergistic impact of the metal center Co species and the phase conjugation of both kinds of MOFs are responsible for this regulatory phenomenon. Therefore, the catalyst demonstrates excellent properties, demonstrating HER 81 mV (η10) in a 1.0 mol L-1 KOH solution and OER 239 mV (η50) low overpotentials. The FeP-CoP3 linked dual electrode alkaline batteries, which are bifunctional electrocatalysts, have a good electrocatalytic ability and may last for 50 h. They require just 1.49 V (η50) for total water breakdown. Through this technique, the electrical structure of electrocatalysts may be altered to increase catalytic activity.

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Mild polarization electric field in ultra-thin BN-Fe-graphene sandwich structure for efficient nitrogen reduction Ziyuan Xiu, Wei Mu, Xin Zhou, Xiaojun Han 2024, 65:  126-137.  DOI: 10.1016/S1872-2067(24)60114-2 Abstract ( 70 )   HTML ( 5 )   PDF (6592KB) ( 30 )   Supporting Information The electrocatalytic N2 reduction reaction (NRR) is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions. The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst, correct electron transfer direction, and electron tunneling distance between bare electrode and active sites. By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method, an ultrathin sandwich catalyst, i.e., Fe atoms (polarized electric field layer) sandwiched between ultrathin (within electron tunneling distance) BN (catalyst layer) and graphene film (conducting layer), is fabricated for electrocatalytic NRR. The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure. The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9 μg h-1 cm-2 and Faradaic Efficiency of 21.7%. The N2 adsorption, activation, and polarization electric field changes of three sandwich catalysts (BN-Fe-G, BN-Fe-BN, and G-Fe-G) during the electrocatalytic NRR are investigated by experiments and density functional theory simulations. Driven by applied voltage, the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.

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Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO2 and methanol over ceria catalysts Lei Dong, Shengjie Zhu, Yangyang Yuan, Xiaomin Zhang, Xiaowei Zhao, Yanping Chen, Lei Xu 2024, 65:  138-152.  DOI: 10.1016/S1872-2067(24)60091-4 Abstract ( 138 )   HTML ( 8 )   PDF (29301KB) ( 88 )   Supporting Information The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes. Herein, a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO2 and methanol, and the structure-performance relationship was investigated in detail. Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies indicated that the adsorption rate of methanol is slower than that of CO2 and the methanol activation state largely influences the formation of key intermediate. Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO2, the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation. Moreover, with the use of 2-cyanopyridine as a dehydration reagent, the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

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Efficient electrocatalytic urea synthesis from CO2 and nitrate over the scale-up produced FeNi alloy-decorated nanoporous carbon Zuo-Shu Sun, Xue-Yan Xiang, Qiu-Ping Zhao, Zhao Tang, Shi-Yi Jiang, Tong-Bu Lu, Zhi-Ming Zhang, Baifan Wang, Hua-Qing Yin 2024, 65:  153-162.  DOI: 10.1016/S1872-2067(24)60111-7 Abstract ( 74 )   HTML ( 5 )   PDF (2501KB) ( 31 )   Supporting Information Electrocatalytic urea synthesis provides a favorable strategy for conventional energy-consuming urea synthesis, but achieving large-scale catalyst synthesis with high catalytic efficiency remains challenging. Herein, we developed a simple method for the preparation of a series of FeNi-alloy-based catalysts, named FeNi@nC-T (n represents the content of nanoporous carbon as 1, 3, 5, 7 or 9 g and T = 900, 950, 1000 or 1100 °C), for highly performed urea synthesis via NO3- and CO2 co-reduction. The FeNi@7C-1000 achieved a high urea yield of 1041.33 mmol h-1 gFeNi-1 with a Faradaic efficiency of 15.56% at -1.2 V vs. RHE. Moreover, the scale-up synthesized FeNi@7C-950-S (over 140 g per batch) was achieved with its high catalytic performance and high stability maintained. Mechanism investigation illuminated that the Ni and Fe sites catalyze and stabilize the key *CO and *N intermediates and minimize the C-N coupling reaction barriers for highly efficient urea synthesis.

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Unraveling the roles of atomically-dispersed Au in boosting photocatalytic CO2 reduction and aryl alcohol oxidation Jian Lei, Nan Zhou, Shuaikang Sang, Sugang Meng, Jingxiang Low, Yue Li 2024, 65:  163-173.  DOI: 10.1016/S1872-2067(24)60109-9 Abstract ( 55 )   HTML ( 6 )   PDF (3317KB) ( 22 )   Supporting Information Atomically-dispersed metal-based materials represent an emerging class of photocatalysts attributed to their high catalytic activity, abundant surface active sites, and efficient charge separation. Nevertheless, the roles of different forms of atomically-dispersed metals (i.e., single-atoms and atomic clusters) in photocatalytic reactions remain ambiguous. Herein, we developed an ethylenediamine (EDA)-assisted reduction method to controllably synthesize atomically dispersed Au in the forms of Au single atoms (AuSA), Au clusters (AuC), and a mixed-phase of AuSA and AuC (AuSA+C) on CdS. In addition, we elucidate the synergistic effect of AuSA and AuC in enhancing the photocatalytic performance of CdS substrates for simultaneous CO2 reduction and aryl alcohol oxidation. Specifically, AuSA can effectively lower the energy barrier for the CO2→*COOH conversion, while AuC can enhance the adsorption of alcohols and reduce the energy barrier for dehydrogenation. As a result, the AuSA and AuC co-loaded CdS show impressive overall photocatalytic CO2 conversion performance, achieving remarkable CO and BAD production rates of 4.43 and 4.71 mmol g−1 h−1, with the selectivities of 93% and 99%, respectively. More importantly, the solar-to-chemical conversion efficiency of AuSA+C/CdS reaches 0.57%, which is over fivefold higher than the typical solar-to-biomass conversion efficiency found in nature (ca. 0.1%). This study comprehensively describes the roles of different forms of atomically-dispersed metals and their synergistic effects in photocatalytic reactions, which is anticipated to pave a new avenue in energy and environmental applications.

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Interfacial coordination bonds accelerate charge separation for unprecedented hydrogen evolution over S-scheme heterojunction Chunxue Li, Hao Lu, Guixiang Ding, Tianyi Ma, Shiyong Liu, Li Zhang, Guangfu Liao 2024, 65:  174-184.  DOI: 10.1016/S1872-2067(24)60108-7 Abstract ( 87 )   HTML ( 7 )   PDF (9227KB) ( 39 )   Supporting Information Inspired by natural photosynthesis, fabricating high-performance S-scheme heterojunction is regarded as a successful tactic to address energy and environmental issues. Herein, NH2-MIL-125(Ti)/Zn0.5Cd0.5S/NiS (NMT/ZCS/NiS) S-scheme heterojunction with interfacial coordination bonds is successfully synthesized through in-situ solvothermal strategy. Notably, the optimal NMT/ZCS/NiS S-scheme heterojunction exhibits comparable photocatalytic H2 evolution (PHE) rate of about 14876.7 μmol h-1 g-1 with apparent quantum yield of 24.2% at 420 nm, which is significantly higher than that of recently reported MOFs-based photocatalysts. The interfacial coordination bonds (Zn-N, Cd-N, and Ni-N bonds) accelerate the separation and transfer of photogenerated charges, and the NiS as cocatalyst can provide more catalytically active sites, which synergistically improve the photocatalytic performance. Moreover, theoretical calculation results display that the construction of NMT/ZCS/NiS S-scheme heterojunction also optimize the binding energy of active site-adsorbed hydrogen atoms to enable fast adsorption and desorption. Photoassisted Kelvin probe force microscopy, in-situ irradiation X-ray photoelectron spectroscopy, femtosecond transient absorption spectroscopy, and theoretical calculations provide sufficient evidence of the S-scheme charge migration mechanism. This work offers unique viewpoints for simultaneously accelerating the charge dynamics and optimizing the binding strength between the active sites and hydrogen adsorbates over S-scheme heterojunction.

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Activating d10 electronic configuration to regulate p-band centers as efficient active sites for solar energy conversion into H2 by surface atomic arrangement Shanshan Lai, Jiakun Su, Shujuan Jiang, Jianjun Zhang, Shaoqing Song 2024, 65:  185-194.  DOI: 10.1016/S1872-2067(24)60119-1 Abstract ( 62 )   HTML ( 2 )   PDF (3264KB) ( 31 )   Supporting Information Relationship between the activity for photocatalytic H2O overall splitting (HOS) and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram, and specially the d10 electronic configuration in valley bottom exhibits inert activity, which seriously fetters the development of catalytic materials with great potentials. Herein, In d10 electronic configuration of In2O3 was activated by phosphorus atoms replacing its lattice oxygen to regulate the collocation of the ascended In 5p-band (In ε5p) and descended O 2p-band (O ε2p) centers as efficient active sites for chemisorption to *OH and *H during forward HOS, respectively, along with a declined In 4d-band center (In ε4d) to inhibit its backward reaction. A stable STH efficiency of 2.23% under AM 1.5 G irradiation at 65 °C has been obtained over the activated d10 electronic configuration with a lowered activation energy for H2 evolution, verified by femtosecond transient absorption spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations of dynamics. These findings devote to activating d10 electronic configuration for resolving the reaction energy barrier and dynamical bottleneck of forward HOS, which expands the exploration of high-efficiency catalytic materials.

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Ab initio molecular dynamics simulation reveals the influence of entropy effect on Co@BEA zeolite-catalyzed dehydrogenation of ethane Yumeng Fo, Shaojia Song, Kun Yang, Xiangyang Ji, Luyuan Yang, Liusai Huang, Xinyu Chen, Xueqiu Wu, Jian Liu, Zhen Zhao, Weiyu Song 2024, 65:  195-205.  DOI: 10.1016/S1872-2067(24)60116-6 Abstract ( 77 )   HTML ( 3 )   PDF (3876KB) ( 25 )   Supporting Information The C-H bond activation in alkane dehydrogenation reactions is a key step in determining the reaction rate. To understand the impact of entropy, we performed ab initio static and molecular dynamics free energy simulations of ethane dehydrogenation over Co@BEA zeolite at different temperatures. AIMD simulations showed that a sharp decrease in free energy barrier as temperature increased. Our analysis of the temperature dependence of activation free energies uncovered an unusual entropic effect accompanying the reaction. The unique spatial structures around the Co active site at different temperatures influenced both the extent of charge transfer in the transition state and the arrangement of 3d orbital energy levels. We provided explanations consistent with the principles of thermodynamics and statistical physics. The insights gained at the atomic level have offered a fresh interpretation of the intricate long-range interplay between local chemical reactions and extensive chemical environments.

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Highly selective electrosynthesis of imines via electroreduction coupling of nitroarenes with aryl aldehydes on Co9S8 with positively charged sulfur vacancies Dianke Xie, Tianyi Yang, Chongyang Ma, Chung-Li Dong, Shuangyin Wang, Yuqin Zou 2024, 65:  206-216.  DOI: 10.1016/S1872-2067(24)60115-4 Abstract ( 85 )   HTML ( 8 )   PDF (6242KB) ( 38 )   Supporting Information The electrocatalytic synthesis of imines through the reductive imination of nitroarenes with aldehydes is a facile, environmentally friendly, and valuable process. In this study, high selectivity electrosynthesis of imines was realized through the electrocatalytic C-N coupling reaction between nitroarenes and aryl aldehydes on Co9S8 nanoflowers with rich sulfur vacancies (Co9S8-Vs). Comparative experiments revealed that positively charged sulfur vacancies play a pivotal role in boosting catalytic selectivity towards imines. Electron-deficient sulfur vacancies intensified the adsorption of negatively charged Ph-NO2, thereby enhancing the conversion rate of the electrochemical nitrobenzene-reduction reaction (eNB-RR). Simultaneously, sulfur vacancies augmented the adsorption capability of negatively charged Ph-CHO, enriching Ph-CHO species at the electrode interface and expediting the Schiff base condensation reaction rate. The experimental results show that the reaction conditions can satisfy the different nitroarenes and aryl aldehydes in the electrocatalytic aqueous-phase system under mild conditions to obtain the corresponding imine products in high selectivity. This study provides a facile and environmentally friendly pathway for future electrocatalytic synthesis of imine.