List of Issues

Chinese Journal of Catalysis
2021, Vol. 42, No. 5
Online: 18 May 2021

Previous Issue    Next Issue

Cover: Liang and coworkers summarized the current work concerning gold catalysts supported by unreducible materials. The currently prevailing synthesis and modification strategies have been reviewed, and the corresponding influences on micro-structure and synergy between compositions have been discussed. Read more about the article behind the cover on pages 670–693.

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Highlight

Select

A new heterojunction in photocatalysis: S-scheme heterojunction S. Wageh, Ahmed A. Al-Ghamdi, Rashida Jafer, Xin Li, Peng Zhang 2021, 42 (5):  667-669.  DOI: 10.1016/S1872-2067(20)63705-6 Abstract ( 5745 )   HTML ( 319 )   PDF (912KB) ( 2407 )

Reviews

Select

Development of gold catalysts supported by unreducible materials: Design and promotions Jingjie Luo, Yanan Dong, Corinne Petit, Changhai Liang 2021, 42 (5):  670-693.  DOI: 10.1016/S1872-2067(20)63743-3 Abstract ( 284 )   HTML ( 22 )   PDF (13677KB) ( 669 )   Gold catalysis had been considered a highly efficient candidate for heterogeneous catalysis. It is well established that reducible-material-supported Au NPs are more reactive than the unreducible materials, unless specific modifications are carried out. However, unreducible materials such as carbon materials, silica, and alumina have particular advantages, including the easily controlled surface property, adjustable microscopic structure, earth-abundant reserves, and facile industrial manufacture. New strategies, influences, and mechanisms of modification to enhance the catalytic performance and thermal stability of unreducible-material-supported gold catalysts are among the most attractive research topics in gold catalysis. However, to the best of our knowledge, reports and reviews focused on unreducible-material-supported gold catalysts are lacking. Herein, the above concept will be thoroughly discussed regarding several typical unreducible supports, including the commonly used silica, alumina, carbon materials, and hydroxyapatite. The currently prevailing modification strategies will be summarized in detail from the aspects of theoretical conceptualization and practical methodology, including the ingenious synthesis method for catalyst with a specific structure, the currently prosperous electrostatic adsorption, colloid immobilization, and the applicative thermal gaseous treatment. The influences of physical and chemical modifications on the surface chemistry, electronic structure, interaction/synergy between Au-support/promoter, catalyst morphology and water precipitation will be also summarized. It is assumed that the review will shed light on significant studies on unreducible support in gold catalysis with the purpose of catalytic promotion and the promotion of the potential industrial demands in advance. Furthermore, the review will provide new insights into unreducible supports that can be potentially applied in gold catalysis.

Select

Stabilization of heterogeneous hydrogenation catalysts for the aqueous-phase reactions of renewable feedstocks Xiaoyan Liu, Guojun Lan, Zhenqing Li, Lihua Qian, Jian Liu, Ying Li 2021, 42 (5):  694-709.  DOI: 10.1016/S1872-2067(20)63699-3 Abstract ( 175 )   HTML ( 14 )   PDF (4138KB) ( 424 )   The conversion of biomass-derived products to fine chemicals and fuels is extremely important for the utilization of renewable energy sources. Water is not only a by-product formed during the hydrogenation of biomass-derived oxygenated chemicals, but also an inexpensive and nontoxic solvent. The instability of solid catalysts for aqueous-phase reactions caused by metal leaching and the collapse of a catalyst support represents a significant challenge. In this work, various catalyst stabilization strategies including the nanospace and interfacial confinements that prevent sintering and leaching of metal nanoparticles as well as modification methods for increasing the support stability are summarized and systemically discussed. In addition, feasible approaches to designing stable and efficient heterogeneous catalysts for aqueous-phase reactions are proposed.

Select

Advances in designing heterojunction photocatalytic materials Zongpeng Wang, Zhiping Lin, Shijie Shen, Wenwu Zhong, Shaowen Cao 2021, 42 (5):  710-730.  DOI: 10.1016/S1872-2067(20)63698-1 Abstract ( 3022 )   HTML ( 192 )   PDF (5939KB) ( 2072 )   Under the background of increasing energy crisis and global warming, semiconductor-based photocatalysis has received tremendous attention due to its potential application in green energy production, CO2 reduction and pollutant degradation. The photocatalytic activity of semiconductors, however, remains low due to issues like fast recombination of photo-generated electron-hole pairs, limited electron mobility, restricted optical absorption or insufficient active sites. Designing appropriate heterojunctions is proved to be a promising method to address most of these issues and thus to improve the photocatalytic performance. In this review, the working mechanism of various heterojunctions is presented systematically. The most recent advances of strategies in designing and preparing efficient heterojunction photocatalysts are further summarized and some perspectives on the future directions in this field are provided.

Select

N-Radical enabled cyclization of 1,n-enynes Wen-Ting Wei, Qiang Li, Ming-Zhong Zhang, Wei-Min He 2021, 42 (5):  731-742.  DOI: 10.1016/S1872-2067(20)63702-0 Abstract ( 214 )   HTML ( 13 )   PDF (1122KB) ( 433 )   Compared to the widely used carbon-centered radicals, N-radicals have been relatively unexplored owing to the lack of practical and convenient production methods. Over the past few years, benefitting from the resurgence of reliable and controllable radical chemistry, N-radicals have been produced via thermal decomposition, oxidants, metal salts, or electrocatalysis. Therefore, numerous N-radical enabled cyclization of 1,n-enynes methods have been developed, providing a versatile and concise synthetic platform for the preparation of complex cyclic systems and natural products containing elaborate ring frameworks. In this review, we will summarize recent advances in the promising field of radical chemistry focusing on the production methods of N-radicals and their cyclization patterns, associated mechanisms, unmet challenges, and future opportunities.

Articles

Select

Enhanced photocatalytic H2 production performance of CdS hollow spheres using C and Pt as bi-cocatalysts Shipeng Tang, Yang Xia, Jiajie Fan, Bei Cheng, Jiaguo Yu, Wingkei Ho 2021, 42 (5):  743-752.  DOI: 10.1016/S1872-2067(20)63695-6 Abstract ( 310 )   HTML ( 10 )   PDF (5270KB) ( 529 )   Photocatalytic H2 production from water splitting is an effective method to solve energy crisis and environmental pollution simultaneously. Herein, carbon@CdS composite hollow spheres (C@CdS-HS) are fabricated via a facile hydrothermal method using porous carbon hollow spheres (C-HS) as the template. The C@CdS-HS shows an excellent photocatalytic H2-generation rate of 20.9 mmol h-1 g-1 (apparent quantum efficiency of 15.3% at 420 nm), with 1.0 wt% Pt as a cocatalyst under simulated sunlight irradiation; this rate is 69.7, 13.9, and 3.9 times higher than that obtained with pure CdS hollow spheres (CdS-HS), C@CdS-HS, and CdS-HS/Pt, respectively. The enhanced photocatalytic H2-evolution activity of C@CdS-HS/Pt is due to the synergistic effect of C and Pt as the bi-cocatalyst. The C-HS serves not only as an active site provider but also as an electron transporter and reservoir. Moreover, C-HS has a strong photothermal effect that is induced by near infrared light, which kinetically accelerates the H2-production reaction. Additionally, the underlying charge transfer pathway and process from CdS to C-HS is revealed. This work highlights the potential application of C-HS-based nanocomposites in solar-to-chemical energy conversion.

Select

Fabricating high-loading Fe-N4 single-atom catalysts for oxygen reduction reaction by carbon-assisted pyrolysis of metal complexes Jun-Sheng Jiang, He-Lei Wei, Ai-Dong Tan, Rui Si, Wei-De Zhang, Yu-Xiang Yu 2021, 42 (5):  753-761.  DOI: 10.1016/S1872-2067(20)63689-0 Abstract ( 436 )   HTML ( 18 )   PDF (2612KB) ( 594 )   Supporting Information Iron-based single-atom catalysts with nitrogen-doped carbon as support (Fe-SA/NPC) are considered effective alternatives to replace Pt-group metals for scalable application in fuel cells. However, synthesizing high-loading Fe-SA catalysts by a simple procedure remains challenging. Herein, we report a high-loading (7.5 wt%) Fe-SA/NPC catalyst prepared by carbon-assisted pyrolysis of metal complexes. Both the nitrogen-doped porous carbon (NPC) support with high specific surface area and ο-phenylenediamine (o-PD) play key roles role in the preparation of high-loading Fe-SA/NPC catalysts. The results of X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption fine structure spectroscopy experiments show that the Fe atoms are anchored on the carbon carriers in a single-atom site configuration and coordinated with four of the doped nitrogen atoms of the carbon substrates (Fe-N4). The activities of the Fe-SA/NPC catalysts in the oxygen reduction reaction increased with increasing iron loading. The optimized 250Fe-SA/NPC-800 catalyst exhibited an onset potential 0.97 V of and a half-wave potential of 0.85 V. Our study provides a simple approach for the large-scale synthesis of high-loading single-atom catalysts.

Select

An effective CdS/Ti-Fe2O3 heterojunction photoanode: Analyzing Z-scheme charge-transfer mechanism for enhanced photoelectrochemical water-oxidation activity Yinyin Li, Qiannan Wu, Qijing Bu, Kai Zhang, Yanhong Lin, Dejun Wang, Xiaoxin Zou, Tengfeng Xie 2021, 42 (5):  762-771.  DOI: 10.1016/S1872-2067(20)63700-7 Abstract ( 389 )   HTML ( 16 )   PDF (2400KB) ( 505 )   Supporting Information Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical (PEC) water splitting. Among the many obstacles facing a Z-scheme photocatalytic system, the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge. Hence, in this study, CdS/Ti-Fe2O3 heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting. In this study, photophysical measurements, including the Kelvin probe measurement, surface photovoltage spectroscopy (SPV), and transient photovoltage spectroscopy (TPV), are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe2O3 Z-scheme heterojunction photoanodes. The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe2O3 interfacial driving force favors the rapid transfer of photoexcited electrons to CdS. The double-beam strategy based on TPV indicates that more electrons of Ti-Fe2O3 are combined with the holes of CdS owing to the intensive interface electric field. The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe2O3 photoanodes. Benefiting from the desirable charge transfer at the interface electric field, CdS/Ti-Fe2O3 photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe2O3. The photocurrent density of the 25CdS/Ti-Fe2O3 photoanode reaches 1.94 mA/cm2 at 1.23 V versus reversible hydrogen electrode without excess cocatalyst, and it is two times higher than that of pure Ti-Fe2O3 photoanode. Therefore, an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.

Select

High-quality and deeply excavated PtPdNi nanocubes as efficient catalysts toward oxygen reduction reaction Yanjie Li, Rifeng Wu, Yang Liu, Ying Wen, Pei Kang Shen 2021, 42 (5):  772-780.  DOI: 10.1016/S1872-2067(20)63703-2 Abstract ( 178 )   HTML ( 6 )   PDF (2233KB) ( 397 )   Supporting Information The oxygen reduction reaction (ORR) on the cathode of a polymer electrolyte fuel cell requires the use of a catalyst based on Pt, one of the most expensive metals on the earth. A number of strategies, including optimization of a different metal into the core, have been investigated to enhance the activity of a Pt-based catalyst and thus reduce the loading of Pt. By dedicating to compounding high catalytic activity Pt2.7Pd0.3Ni concave cubic with high index crystal face, the paper shows that concave structures can offer more active site and high level of catalytic activity and if mixed with other metal, decrease the proportion of Pt and improve its mass activity. The paper also makes an exploration into the theory and conditions behind the formation of Pt2.7Pd0.3Ni concave cubic structure, and investigates the difference it demonstrates by modifying the reactive conditions. The results of the oxygen reduction performance of the electrochemical test are as follows: the concave cube-shaped Pt-Pd-Ni catalyst has a mass activity of 1.28 A mgPt-1 at 0.9 V, its highest mass activity is 8.20 times that of commercial Pt/C, and its specific activity is 8.68 times of that commercial Pt/C. And the Pt-Pd-Ni ternary nanocage has excellent structural invariance. After the stability test, there is no obvious structural change and performance degradation in the nanostructure.

Select

MgO and Au nanoparticle Co-modified g-C3N4 photocatalysts for enhanced photoreduction of CO2 with H2O Naixu Li, Meiyou Huang, Jiancheng Zhou, Maochang Liu, Dengwei Jing 2021, 42 (5):  781-794.  DOI: 10.1016/S1872-2067(20)63690-7 Abstract ( 243 )   HTML ( 16 )   PDF (2381KB) ( 601 )   Supporting Information The photoreduction of CO2 to achieve high-value-added hydrocarbons under simulated sunlight irradiation is advantageous, but challenging. In this study, a series of MgO and Au nanoparticle-co-modified g-C3N4 photocatalysts were synthesized and subsequently applied for the photocatalytic reduction of CO2 with H2O under simulated solar irradiation. The best photocatalytic performance was demonstrated by the Au and 3% MgO-co-modified g-C3N4 photocatalysts with CO, CH4, CH3OH, and CH3CHO yields of 423.9, 83.2, 47.2, and 130.4 μmol/g, respectively, in a 3-h reaction. We investigated the effects of MgO and Au as cocatalysts on photocatalytic behaviors, respectively. The characterizations and experimental results showed that the enhanced photocatalytic activity was due to the synergistic effect among the components of the ternary photocatalyst. The cocatalyst MgO can activate CO2 (adsorbed at the interface between the MgO and Au particles), and the Mg-N bonds formed in the MgO-CN nanosheets played an important role in the charge transfer. Meanwhile, the Au particles that were modified into MgO/g-C3N4 can increase the absorption of visible light via the surface plasmon resonance effect and further reduce the activation energies of the photoreduction of CO2 using H2O. This study provided an effective method for the modification of traditional primary photocatalysts with promising performance for photocatalytic CO2 reduction.

Select

Promoting NOx reduction via in situ activation of perovskite supported Pd catalysts under alternating lean-burn/fuel-rich operating atmospheres Dongyue Zhao, Yuexi Yang, Zhongnan Gao, Mengxin Yin, Ye Tian, Jing Zhang, Zheng Jiang, Xiaobo Yu, Xingang Li 2021, 42 (5):  795-807.  DOI: 10.1016/S1872-2067(20)63694-4 Abstract ( 157 )   HTML ( 6 )   PDF (1219KB) ( 454 )   Supporting Information Herein, we report the excellent De-NOx performance of La0.7Sr0.3MnO3 (LSM) perovskite-supported Pd catalysts (Pd-LSM) in alternating lean-burn/fuel-rich atmospheres using C3H6 as reductant and describe the in situ activation of the Pd catalysts via metal-support interaction (MSI) tuning. The NOx reduction conversion of the Pd-LSM catalyst increased significantly from 56.1% to 90.1% and the production of N2O was suppressed. Our results demonstrated that this behavior was mainly attributed to the in situ transformation of Pd2+ into Pd0 during the reaction. The generated Pd0 species could readily activate the C3H6 reductant and achieve an eight-fold higher turnover frequency than Pd2+ for the reduction of NOx. Moreover, excessive MSIs inhibited the in situ generation of Pd0, and thereby, lowered the De-NOx activity of the catalyst even at high Pd dispersion. In addition, the Pd-LSM catalysts exhibited much higher S tolerance than conventional Al2O3-supported catalysts. Our study provides a new approach for analyzing and designing highly active metal catalysts operated under dynamic alternating oxidizing/reducing atmospheric conditions.

Select

Time-resolved infrared spectroscopic investigation of Ga2O3 photocatalysts loaded with Cr2O3-Rh cocatalysts for photocatalytic water splitting Qian Ding, Tao Chen, Zheng Li, Zhaochi Feng, Xiuli Wang 2021, 42 (5):  808-816.  DOI: 10.1016/S1872-2067(20)63688-9 Abstract ( 154 )   HTML ( 13 )   PDF (1316KB) ( 526 )   Supporting Information Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts. In this work, the dynamics of photogenerated electrons in Ga2O3 loaded with Cr2O3-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy. The structure of these Cr2O3-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy, as Rh particles partly covered with Cr2O3. The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction. The loaded Cr2O3 promotes electron transfer from Ga2O3 to Rh, which accelerates the electron-consuming reaction for H2 evolution. Based on these observations, a photocatalytic water-splitting mechanism for Cr2O3-Rh/Ga2O3 photocatalysts has been proposed. The elucidation of the roles of the Cr2O3-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.

Select

Reveal the nature of particle size effect for CO2 reduction over Pd and Au Piaoping Yang, Lulu Li, Zhi-Jian Zhao, Jinlong Gong 2021, 42 (5):  817-823.  DOI: 10.1016/S1872-2067(20)63692-0 Abstract ( 169 )   HTML ( 7 )   PDF (1984KB) ( 451 )   Supporting Information Small cluster and periodic surface models with low coverages of intermediates are frequently employed to investigate reaction mechanisms and identify active sites on nanoparticles (NPs) in density functional theory (DFT) studies. However, diverse active sites on NPs cannot be sufficiently represented by these simple models, hampering the in-depth insights into the catalytic behavior of NPs. This paper describes the crucial roles of both model and coverage effect on understanding the nature of active sites for CO2 reduction over Au and Pd NPs using DFT calculations. Terrace sites exhibit higher selectivity for CO than edge sites on Au NPs, which is opposite to the results on Au periodic surfaces. This contradiction reveals the computational model effect on clarifying active site properties. For Pd catalysts, the coverage effect is more significant. On bare Pd NPs and periodic surfaces, the selectivity for CO at edge sites is nearly identical to that at terrace sites, whereas edge sites display higher selectivity for CO than terrace sites in the case of high CO coverages. Through considering the more realistic models and the coverage effect, we successfully describe the size effect of Au and Pd NPs on CO selectivity. More importantly, this work reminds us of the necessity of reasonable models in DFT calculations.

Select

MIL-53 (Al) derived single-atom Rh catalyst for the selective hydrogenation of m-chloronitrobenzene into m-chloroaniline Weiyin Wang, Lu Lin, Haifeng Qi, Wenxiu Cao, Zhi Li, Shaohua Chen, Xiaoxuan Zou, Tiehong Chen, Nanfang Tang, Weiyu Song, Aiqin Wang, Wenhao Luo 2021, 42 (5):  824-834.  DOI: 10.1016/S1872-2067(20)63697-X Abstract ( 215 )   HTML ( 7 )   PDF (6808KB) ( 529 )   Supporting Information The catalytic hydrogenation of halonitroarenes to haloanilines is a green and sustainable process for the production of key nitrogen-containing intermediates in fine chemical industry. Chemoselective hydrogenation poses a significant challenge, which requires the rational design of the catalysts with proper hydrogenation ability for nitro group and simultaneously preventing dehalogenation of halogen group. Herein, a highly effective Rh@Al2O3@C single-atom catalyst (SAC) was developed for the hydrogenation of m-chloronitrobenzene (m-CNB) to m-chloroaniline (m-CAN), through an in-situ grafting of metal during the assembly of MIL-53 (Al), followed by confined pyrolysis. Extensive characterizations reveal an exquisite structure of the Rh@Al2O3@C, containing atomically dispersed Rh sites onto Al2O3 confined by the amorphous carbon. The five-coordinated aluminum (AlV) species are essential for achieving the atomic dispersion of Rh atoms, providing the unsaturated coordinative sites for metal. Compared to the benchmark Rh/γ-Al2O3 and Rh/C nanocatalysts, the Rh@Al2O3@C SAC affords an excellent turnover frequency of 2317 molm-CNB·molRh-1·h-1, the highest value to date in heterogeneous catalyst systems for the hydrogenation of m-CNB at 313 K and 20 bar H2, together with a sustained selectivity to m-CAN (~98%) during five consecutive runs. The superior catalytic performance of the Rh@Al2O3@C is attributed to a proper modulation of electronic structure of hydrogenation metal by forming SAC, together with an enhanced accessibility of acid function sites.

Select

The carboxylates formed on oxides promoting the aromatization in syngas conversion over composite catalysts Zhiyang Chen, Youming Ni, Fuli Wen, Ziqiao Zhou, Wenliang Zhu, Zhongmin Liu 2021, 42 (5):  835-843.  DOI: 10.1016/S1872-2067(20)63691-9 Abstract ( 166 )   HTML ( 7 )   PDF (953KB) ( 411 )   Supporting Information Syngas to aromatics (STA) over bifunctional catalysts has attracted much attention in recent years, but the mechanism underlying the formation of aromatics remains controversial. The critical reaction intermediates, carboxylates, were first identified and then confirmed to essentially promote aromatization in the syngas conversion over a ZnCrAlOx&H-ZSM-5 composite catalyst. This study provides evidence that the carboxylates can be formed during the reactions of formate species and olefins. In addition, it is shown that the carboxylates favor the formation of aromatics over H-ZSM-5 even in the presence of H2. A novel mechanism for the formation of aromatics via the generation and transformation of carboxylate intermediates is proposed, and the transformation of carboxylates to aromatics via methyl-2-cyclopenten-1-one (MCPO) intermediates is indeed likely. A better understanding of the formation mechanism of aromatics would help optimize the composite catalyst.

Select

Production of bio-ethanol by consecutive hydrogenolysis of corn-stalk cellulose Dawang Chu, Yingying Xin, Chen Zhao 2021, 42 (5):  844-854.  DOI: 10.1016/S1872-2067(20)63709-3 Abstract ( 485 )   HTML ( 18 )   PDF (1939KB) ( 508 )   Supporting Information Current bio-ethanol production entails the enzymatic depolymerization of cellulose, but this process shows low efficiency and poor economy. In this work, we developed a consecutive aqueous hydrogenolysis process for the conversion of corn-stalk cellulose to produce a relatively high concentration of bio-ethanol (6.1 wt%) without humin formation. A high yield of cellulose (ca. 50 wt%) is extracted from corn stalk using a green solvent (80 wt% 1,4-butanediol) without destroying the structure of the lignin. The first hydrothermal hydrogenolysis step uses a Ni-WOx/SiO2 catalyst to convert the high cumulative concentration of cellulose (30 wt%) into a polyol mixture with a 56.5 C% yield of ethylene glycol (EG). The original polyol mixture is then subjected to subsequent selective aqueous-phase hydrogenolysis of the C-O bond to produce bioethanol (75% conversion, 84 C% selectivity) over the modified hydrothermally stable Cu catalysts. The added Ni component favors the good dispersion of Cu nanoparticles, and the incorporated Au3+ helps to stabilize the active Cu0-Cu+ species. This multi-functional catalytic process provides an economically competitive route for the production of cellulosic ethanol from raw lignocellulose.