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Chinese Journal of Catalysis
2023, Vol. 52
Online: 18 September 2023

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Cover: Professor Aiwen Lei and coworkers develop an electrochemically enabled regioselective ortho-(4 + 2)/ipso-(3 + 2) cyclization of alkyl/alkenyl radicals with aryl groups, which provided a series of tetrahydronaphthalene and spirocarbocycle derivatives. Importantly, this strategy is regarded as an important supplement of Baldwin’s rules for radical cyclization. Read more about the article behind the cover on page 144–153.

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Single-atom catalysts: In search of the holy grails in catalysis Sikai Wang, Xiang-Ting Min, Botao Qiao, Ning Yan, Tao Zhang 2023, 52:  1-13.  DOI: 10.1016/S1872-2067(23)64505-X Abstract ( 778 )   HTML ( 78 )   PDF (6922KB) ( 779 )   This perspective assesses the recent progress using single-atom catalysts for five “holy grail” reactions, including partial methane oxidation to methanol, non-oxidative methane conversion, photocatalytic CO2 reduction, photocatalytic water splitting, and nitrogen activation. Using selected case studies, we discuss promising efforts in these domains and at the same time identify the remaining challenges in using SACs for selective and efficient chemical transformations across thermal, electrical, and light-driven catalysis. Looking forward, we highlight the significant potential of SAC research in areas like mechanistic studies, high-throughput screening, and novel catalytic system design.

Reviews

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Strategies for efficient CO2 electroreduction in acidic conditions Xinyi Zou, Jun Gu 2023, 52:  14-31.  DOI: 10.1016/S1872-2067(23)64511-5 Abstract ( 807 )   HTML ( 80 )   PDF (10676KB) ( 805 )   CO2 electroreduction is a promising technique to convert renewable electricity and CO2 to high-value fuels and chemicals. Selectivity, energy efficiency, carbon efficiency and sustainability are the criteria for CO2 electroreduction techniques suitable for industrial application. With alkaline and neutral electrolytes, carbonate formation from CO2 leads to low carbon efficiency. High energy consumption to regenerate alkaline electrolyte and high resistance of neutral electrolyte cause low energy efficiency. Recently, CO2 reduction with acidic electrolyte becomes a hot topic due to its potential to increase carbon efficiency and energy efficiency. Improving the selectivity towards CO2 reduction is challenging in acidic condition. Diverse approaches were proposed to suppress H+ reduction and promote CO2 reduction. However, fundamental issues about cation effect and local pH effect on CO2 reduction in acidic condition are still under debate. Moreover, bicarbonate precipitation in gas diffusion electrode limits the sustainability with acidic electrolyte. This review tries to rationalize the reported strategies to improve the selectivity towards CO2 reduction in acidic condition from mass transport and electrode reactions. Different approaches, including adding alkali cations, surface decoration, nanostructuring, and electronic structure modulation, are designed based on these two aspects. This review also introduces the recent progress in CO2 electroreduction with metal cation-free acidic electrolyte. This strategy is deemed to improve the sustainability.

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A review on ZnO-based S-scheme heterojunction photocatalysts Zicong Jiang, Bei Cheng, Liuyang Zhang, Zhenyi Zhang, Chuanbiao Bie 2023, 52:  32-49.  DOI: 10.1016/S1872-2067(23)64502-4 Abstract ( 288 )   HTML ( 34 )   PDF (22274KB) ( 488 )   ZnO, a typical photocatalyst, has aroused great attention due to its nontoxicity, biocompatibility, and earth abundance. However, its performance is hindered by insufficient light absorption capacity, limited reduction ability, and fast recombination of photogenerated carriers (PC). To overcome these challenges, the construction of ZnO-based S-scheme heterojunctions has emerged as an effective solution, enabling the simultaneous realization of spatially separated PC and enhanced redox abilities. Given the notable progress in ZnO-based S-scheme heterojunctions, it is crucial to review the current achievements and provide guidance for future development. This paper presents the development and representative characterization methods of S-scheme heterojunctions, outlines the design principles of ZnO-based S-scheme heterojunctions, and exemplifies the applications of ZnO-based S-scheme heterojunctions in environmental remediation, hydrogen evolution, H2O2 production, and CO2 reduction. Finally, the significant challenges and potential improvements for ZnO-based S-scheme heterojunction photocatalysts are proposed.

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Recent progress in advanced catalysts for electrochemical nitrogen reduction reaction to ammonia Yan Hong, Qi Wang, Ziwang Kan, Yushuo Zhang, Jing Guo, Siqi Li, Song Liu, Bin Li 2023, 52:  50-78.  DOI: 10.1016/S1872-2067(23)64504-8 Abstract ( 484 )   HTML ( 30 )   PDF (28323KB) ( 383 )   Due to its use of renewable energy and environmental friendliness, the electrochemical nitrogen reduction process (eNRR) has become a promising substitute for the manufacturing of ammonia. Despite extensive exploration of eNRR catalysts, an optimal catalyst has not been reported to date. Therefore, it is imperative to develop rational catalysts to enhance NH3 synthesis efficiency. In order to offer suggestions for catalyst design, recent developments in electrocatalysts for eNRR are summarized in this paper. Firstly, the eNRR mechanism is briefly introduced. Secondly, the design strategies of eNRR catalysts were summarized in terms of morphology, structure, vacancies, doping, synergistic effect, heterojunction and single atom. Subsequently, the application of in situ mass spectrometry, in situ infrared, in situ XAS and in situ Raman to the NRR reaction is discussed. The importance of the density-functional theory (DFT) method for the study of reaction energy barriers and catalyst electron-orbital distributions during eNRR catalysis is discussed. Finally, this review presents the potential challenges and future perspectives of eNRR.

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Single-atom catalysts for the photocatalytic and electrocatalytic synthesis of hydrogen peroxide Xiaolong Tang, Feng Li, Fang Li, Yanbin Jiang, Changlin Yu 2023, 52:  79-98.  DOI: 10.1016/S1872-2067(23)64498-5 Abstract ( 640 )   HTML ( 42 )   PDF (11360KB) ( 554 )   Hydrogen peroxide (H2O2) is widely used as an environmentally friendly oxidant and plays an important role in a range of applications, including chemical synthesis, wastewater treatment, medical disinfection, and papermaking. Compared to the conventional anthraquinone process for the preparation of H2O2, the photocatalytic and electrocatalytic production of H2O2 has the advantages of simple and controllable operating conditions and non-polluting reaction products, which is one of the most essential ideal means for H2O2 production. Among them, single-atom catalysts (SACs) with maximal atom utilization and special unsaturated coordination environments have attracted considerable attention because of their excellent catalytic performance in the photocatalytic and electrocatalytic production of H2O2. Subsequently, recent progress in H2O2 production based on photocatalytic and electrocatalytic activity is presented in this review. First, the working mechanisms and advantages of SACs for the photocatalytic and electrocatalytic production of H2O2 were presented. Second, we combined density functional theory calculations and advanced characterization techniques to introduce SAC systems for H2O2 production. Finally, the future directions of SACs for photocatalytic and electrocatalytic H2O2 production are discussed.

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Recent advances in fermentative production of C4 diols and their chemo-catalytic upgrading to high-value chemicals Abhishek R. Varma, Bhushan S. Shrirame, Sunil K. Maity, Deepti Agrawal, Naglis Malys, Leonardo Rios-Solis, Gopalakrishnan Kumar, Vinod Kumar 2023, 52:  99-126.  DOI: 10.1016/S1872-2067(23)64512-7 Abstract ( 201 )   HTML ( 16 )   PDF (4091KB) ( 183 )   The current era is witnessing the transition from a fossil-dominated economy towards sustainable and low-carbon green manufacturing technologies at economical prices with reduced energy usage. The biological production of chemical building blocks from biomass using cell factories is a potential alternative to fossil-based synthesis. However, microbes have their own limitations in generating the whole spectrum of petrochemical products. Therefore, there is a growing interest in an integrated/hybrid approach where products containing active functional groups obtained by biological upgrading of biomass are converted via chemo-catalytic routes. The present review focuses on the biological production of three important structural isomers of C4 diols, 2,3-, 1,3-, and 1,4-butanediol, which are currently manufactured by petrochemical route to meet the soaring global market demand. The review starts with justifications for the integrated approach and summarizes the current status of the biological production of these diols, including the substrates, microorganisms, fermentation technology and metabolic/pathway engineering. This is followed by a comprehensive review of recent advances in catalytic upgrading of C4 diols to generate a range of products. The roles of various active sites in the catalyst on catalytic activity, product selectivity, and catalyst stability are discussed. The review also covers examples of integrated approaches, addresses challenges associated with developing end-to-end processes for bio-based production of C4 diols, and underlines existing limitations for their upgrading via direct catalytic conversion. Finally, the concluding remarks and prospects emphasise the need for an integrated biocatalytic and chemo-catalytic approach to broaden the spectrum of products from biomass.

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High-crystalline g-C3N4 photocatalysts: Synthesis, structure modulation, and H2-evolution application Binbin Zhao, Wei Zhong, Feng Chen, Ping Wang, Chuanbiao Bie, Huogen Yu 2023, 52:  127-143.  DOI: 10.1016/S1872-2067(23)64491-2 Abstract ( 914 )   HTML ( 36 )   PDF (8804KB) ( 520 )   Graphitic carbon nitride (g-C3N4) has received extensive attention in the photocatalytic field because of its low cost, nontoxicity, suitable bandgap structure, and high physicochemical stability among diverse photocatalysts. However, traditional g-C3N4 materials prepared by the high-temperature calcination of various organic precursors generally exhibit poor crystallinity and possess numerous internal and surface defects, leading to the rapid recombination of photo-excited charges. Constructing a highly crystalline g-C3N4 photocatalyst, as opposed to the traditional poorly crystalline g-C3N4, effectively reduces internal and surface defects, facilitating efficient separation and rapid transfer of photoexcited charges. As a result, the photocatalytic performance is significantly enhanced. In this review, recent progress in highly crystalline g-C3N4 photocatalysts is summarized. The microstructural characteristics of highly crystalline g-C3N4 photocatalysts are discussed in detail. Synthetic methods for highly crystalline g-C3N4, such as the salt-assisted (multicomponent salt and single-component salt), template, two-step calcination method, microwave-assisted method, and others, are meticulously presented. Additionally, various modification strategies for highly crystalline g-C3N4, encompassing bandgap engineering, heterojunction construction, and co-catalyst modification, are presented. Subsequently, a detailed description of the photocatalytic H2-evolution applications of highly crystalline g-C3N4 materials is given. Lastly, the paper concludes with a discussion on the outlook for highly crystalline g-C3N4 photocatalysts, aiming to offer novel insights into the design of highly efficient crystalline g-C3N4 photocatalysts.

Articles

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Regioselective electrochemical oxidative radical ortho-(4 + 2)/ipso-(3 + 2) cyclization Zhipeng Guan, Dongfeng Yang, Zhao Liu, Shuxiang Zhu, Xingxing Zhong, Huamin Wang, Xiangwei Li, Xiaotian Qi, Hong Yi, Aiwen Lei 2023, 52:  144-153.  DOI: 10.1016/S1872-2067(23)64510-3 Abstract ( 177 )   HTML ( 15 )   PDF (1256KB) ( 170 )   Supporting Information Achieving regioselectivity in radical cyclization reactions is of central importance, yet extremely challenging. Although Baldwin’s rules provided guidance on the addition of radical species with alkenes/alkynes, the ortho-/ipso-selectivity of the cyclic reaction between radical species (especially alkyl and alkenyl radical) and aryl groups is still ambiguous. Herein, we develop an electrochemically enabled regioselective ortho-(4 + 2)/ipso-(3 + 2) cyclization of alkyl/alkenyl radicals with aryl groups, which provides a series of tetrahydronaphthalene and spirocarbocycle derivatives, exhibiting a broad substrate scope and functional group tolerance. Alkyl/alkenyl radicals are generated by Cp2Fe-mediated electrochemical oxidative radical addition of benzylic malonates with alkenes and alkynes. The method avoids the use of chemical oxidant/base/noble metal, the pre-functionalization of substrates, and the over-oxidation of compounds. Theoretical studies reveal that the dominant factor promoting the alkene-preferred ortho-addition is the favorable interaction energy; the alkyne-preferred ipso-addition regioselectivity is controlled by the distortion energy. Notably, this strategy is regarded as an important supplement to Baldwin’s rules for radical cyclization.

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The nature of local oxygen radical boosts electrocatalytic ethanol to selectively generate CO2 Shuanglong Zhou, Liang Zhao, Zheng Lv, Yu Dai, Qi Zhang, Jianping Lai, Lei Wang 2023, 52:  154-163.  DOI: 10.1016/S1872-2067(23)64503-6 Abstract ( 169 )   HTML ( 11 )   PDF (1613KB) ( 123 )   Supporting Information Developing a high-activity and antitoxic electrocatalyst is still a demanding task. Enhancing the enrichment of oxygen species on catalysts is beneficial for thorough oxidation of ethanol to generate CO2, but the role of oxygen radicals in the process of ethanol oxidation is still ambiguous. Herein, an artificial oxidase that can catalyze oxygen to generate reactive oxygen species (ROS) in-situ has been applied in EOR for the first time and the roles of •OH, •O2-, and 1O2 in complete oxidation of ethanol were investigated. The mass activity of EOR is 18.2 A mgPt-1 in 1 mol L-1 KOH and the CO2 selectivity is 98.7%. The research showed that Sn element could optimize coordination mode on catalyst surface, which enhanced oxidase activity of the catalyst. Explored the intermediates of the reaction and evaluated the performance of the catalyst using in-situ infrared testing technology. Theoretical calculations indicate that C-C bond breakage of *CH3CO to generate *CH3 and *CO is potential determination steps in the C1 pathway. When singlet oxygen is present on the PtSn IM/C surface, the dissociation energy of C-C bond is -0.51 eV, which is lower than the 1.07 eV of hydroxyl radicals and -0.47 eV of superoxide anions.

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Hollow dodecahedron K3PW12O40/CdS core-shell S-scheme heterojunction for photocatalytic synergistic H2 evolution and benzyl alcohol oxidation Lijuan Sun, Xiaohui Yu, Liyong Tang, Weikang Wang, Qinqin Liu 2023, 52:  164-175.  DOI: 10.1016/S1872-2067(23)64507-3 Abstract ( 184 )   HTML ( 8 )   PDF (3756KB) ( 276 )   Supporting Information Simultaneous generation of clean energy, H2, and organic products holds immense potential in the realm of photocatalysis. The S-scheme heterojunction stands out for these dual-function applications due to its robust redox capacity, facilitating both the water reduction reaction and organic oxidation reactions. In this study, a Keggin-type polymetallic oxide, H3PW12O40 hollow dodecahedron (KPW), was synthesized using a hydrothermal approach. Subsequently, cadmium sulfide (CdS) nanoparticles averaging 15 nm in size were integrated in situ onto the KPW shell, resulting in the creation of a core-shell KPW@CdS S-scheme heterojunction. This optimized composite showcased a hydrogen evolution rate of 18.7 mmol g-1 h-1, alongside a value-added product, benzaldehyde, with a yield of 17.5 mmol g-1 h-1 substantially surpassing the performance of standalone CdS. This S-scheme junction, featuring a pronounced internal electronic field, emerges between the KPW and CdS. It significantly enhances the segregation of photogenerated carriers while preserving formidable redox capability. Furthermore, the hollow structure augments light absorption and utility, and the core-shell architecture delivers dual reduction and oxidation sites. As a result, the interplay between the hollow core-shell configuration and the S-scheme mode intensifies the photocatalytic activity. This research provides an innovative approach to crafting hollow S-scheme heterojunctions, aiming to optimize photocatalytic redox reactions for effective solar energy utilization.

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Bidirectional host-guest interactions promote selective photocatalytic CO2 reduction coupled with alcohol oxidation in aqueous solution Wen Zhang, Cai-Cai Song, Jia-Wei Wang, Shu-Ting Cai, Meng-Yu Gao, You-Xiang Feng, Tong-Bu Lu 2023, 52:  176-186.  DOI: 10.1016/S1872-2067(23)64509-7 Abstract ( 226 )   HTML ( 14 )   PDF (3809KB) ( 260 )   Supporting Information Existing artificial photosynthesis systems often underperform due to challenges in water oxidation and extensive photogenerated carrier transfer. Herein, we demonstrate that β-cyclodextrin-decorated CdS nanocrystals (CdS-CD) can simultaneously anchor cobalt tetraphenyl porphyrin (CoTPP) catalysts and alcohol reductants onto CdS surfaces through bidirectional host-guest interactions between β-CD and CoTPP/alcohol. This configuration ensures swift electron transfer from CdS to β-CD bonded CoTPP, facilitating CO2 reduction to HCOOH. Results showcase a remarkable yield of 1610 μmol g-1 h-1 and a 96.5% selectivity. Meanwhile, photogenerated holes in CdS are efficiently neutralized by β-CD bonded furfuryl alcohol, achieving a furfural yield of 1567 μmol g-1 h-1 and > 99% selectivity. In contrast, the discrete CoTPP-CdS system achieved a HCOOH yield of only 306 μmol g-1 h-1 and a poor HCOOH selectivity of 46.4%. It was also observed that the CoTPP@CdS-CD system maintained high CO2-to-HCOOH conversion rates when using other alcohols as reductants.

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Steering electrochemical carbon dioxide reduction to alcohol production on Cu step sites Hui Gao, Gong Zhang, Dongfang Cheng, Yongtao Wang, Jing Zhao, Xiaozhi Li, Xiaowei Du, Zhi-Jian Zhao, Tuo Wang, Peng Zhang, Jinlong Gong 2023, 52:  187-195.  DOI: 10.1016/S1872-2067(23)64508-5 Abstract ( 256 )   HTML ( 11 )   PDF (2633KB) ( 292 )   Supporting Information Electrochemical CO2 reduction is a sustainable method for producing multicarbon alcohols. However, the selectivity of alcohols is limited owing to the favorable side reaction to convert the key intermediate of *CH2CHO into ethylene. This study describes the design of a Cu electrocatalyst with abundant step sites to suppress the deoxygenation of *CH2CHO to ethylene, thereby promoting alcohol production. A Faradic efficiency of 40.5% and partial current density of 56.3 mA/cm2 for alcohols are achieved. Moreover, the alcohols/C2H4 ratio in the products reaches approximately 2.2. In-situ infrared spectrum characterizations and theoretical calculations reveal that the step sites facilitate C-C coupling and direct the reaction pathway to promote the formation of alcohols by inhibiting the cleavage of the C-O bond in *CH2CHO. Therefore, the proposed strategy is efficient for designing active sites to steer reaction pathways in CO2 electroreductions and produce alcohols.

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In situ constructed dynamic Cu/Ce(OH)x interface for nitrate reduction to ammonia with high activity, selectivity and stability Yong Liu, Xiaoli Zhao, Chang Long, Xiaoyan Wang, Bangwei Deng, Kanglu Li, Yanjuan Sun, Fan Dong 2023, 52:  196-206.  DOI: 10.1016/S1872-2067(23)64506-1 Abstract ( 325 )   HTML ( 13 )   PDF (5286KB) ( 195 )   Supporting Information Electrocatalytic nitrate reduction (NO3‒RR) offers a promising technique for the removal and utilization of nitrate in water. However, the performance of current catalysts is still limited mainly due to the unfavorable interface that largely determines the reaction efficiency and selectivity. Here we present an in situ dynamic reconstruction strategy to enhance the NO3‒RR by constructing Cu/Ce(OH)x catalyst with abundant interfacial active sites. The Cu/Ce(OH)x catalyst was in situ formed through dynamic reconstruction of Cu2Cl(OH)3/Ce(OH)x heterostructure during electrochemical NO3‒RR process. The catalyst exhibits high performance with NO3‒ conversion of 100.0%, NH3 selectivity of 97.8%, NH3 Faradaic efficiency of 99.2% and long stability, which is among the state-of-the-art catalysts in neutral media. Both experimental and theoretical results demonstrate that the Cu and Ce sites at the interface can operate cooperatively to promote the adsorption and activation of NO3‒, and lower the formation energy of key intermediate *HNO. Meanwhile, the hydrogen evolution reaction is also greatly suppressed due to the high H* binding strength at the interface. The strategy can be extended to other catalytic systems and opens a new avenue for the design of efficient electrocatalysts.

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Construction of modularized catalytic system for transfer hydrogenation: Promotion effect of hydrogen bonds Xin Liu, Maodi Wang, Yiqi Ren, Jiali Liu, Huicong Dai, Qihua Yang 2023, 52:  207-216.  DOI: 10.1016/S1872-2067(23)64499-7 Abstract ( 203 )   HTML ( 11 )   PDF (3768KB) ( 231 )   Supporting Information The construction of enzyme-mimicking catalysts is a crucial route for achieving green chemical transformations; however, integrating multiple sites into one catalyst is challenging. Herein, a facile method is reported to combine different active sites by constructing a modularized catalytic system. A modularized catalytic system composed of covalent organic frameworks (COFs) and Cu2Cr2O5 exhibits remarkable efficiency in the transfer hydrogenation of cinnamaldehyde, with a selectivity of over 99% towards cinnamyl alcohol, surpassing the reaction rate of Cu2Cr2O5 by more than fourfold. The results of the mechanistic study and density functional theory calculations suggest that the enhanced activity of the modularized catalytic system is derived from the hydrogen bonds between the COFs and isopropyl alcohol, which promote isopropyl alcohol dehydrogenation and hydride transfer. In addition, the modularized catalytic system is efficient for various saturated and unsaturated aldehydes and could be replaced by different submodules. This study demonstrates the efficiency of a modularized catalytic system for mimicking the functions of enzymes in catalysis.

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Role of oxygen transfer and surface reaction in catalytic performance of VOx-Ce1‒xZrxO2 for propane dehydrogenation Jiachen Sun, Sai Chen, Donglong Fu, Wei Wang, Xianhui Wang, Guodong Sun, Chunlei Pei, Zhi-Jian Zhao, Jinlong Gong 2023, 52:  217-227.  DOI: 10.1016/S1872-2067(23)64494-8 Abstract ( 239 )   HTML ( 20 )   PDF (2252KB) ( 207 )   Supporting Information The bulk oxygen transfer and surface reaction as important parts of the chemical looping-related process are crucial for the rational design of new redox catalysts. This paper describes an experimental study on the effect of bulk oxygen transfer and surface reaction in Ce1‒xZrxO2 supported VOx redox catalysts for the chemical looping oxidative propane dehydrogenation reaction. It was found that the introduction of Zr dictates the reaction performance of the redox catalyst by modulating the bulk oxygen transfer and surface reaction. The kinetic study reveals that the instantaneous reduction rate of the redox catalysts is determined by the H-abstraction step in the surface reaction. The introduction of Zr can reduce the activation energy of the H-abstraction step, which leads to the enhancement of the instantaneous reduction rate. Meanwhile, the oxygen supply capacity of the cerium oxide is increased by Zr, allowing the surface reaction to proceed over longer durations. Furthermore, the reaction model derived from the kinetics study is validated using a number of (quasi) in situ techniques. This study provides fundamental insights into the role of bulk oxygen transfer and surface reaction in chemical looping or related process.

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Ultrafast carbothermal shock strategy enabled highly graphitic porous carbon supports for fuel cells Mingjia Lu, Lecheng Liang, Binbin Feng, Yiwen Chang, Zhihong Huang, Huiyu Song, Li Du, Shijun Liao, Zhiming Cui 2023, 52:  228-238.  DOI: 10.1016/S1872-2067(23)64495-X Abstract ( 416 )   HTML ( 28 )   PDF (2899KB) ( 335 )   Supporting Information The electronic conductivity and durability of porous carbon supports can be improved by increasing the degree of graphitization in the material; however, the preparation of highly graphitic porous carbon using conventional furnaces remains a significant challenge. Herein, we demonstrate a universal and highly efficient carbothermal shock strategy that significantly improves the degree of graphitization of porous carbon supports, including bowl-like carbon, hollow carbon spheres, ZIF8-derived carbon, BP2000, and Ketjen EC 300J. Taking bowl-like carbon as an example, we illustrate the synthesis of a graphitized bowl-like carbon (G-BC-S) support and evaluate the performance of PtCo/G-BC-S in the oxygen reduction reaction (ORR) in rotating disk electrodes (RDE) and H2/air PEM single cells. PtCo/G-BC-S exhibits faster ORR kinetics than PtCo/BC and Pt/C, with little loss of activity (25%) and only 13 mV of E1/2 decay after 20000 cycles accelerated stress testing under 1.0-1.5 V vs. a reversible hydrogen electrode (RHE). The significantly enhanced performance of the PtCo/G-BC-S catalyst arises from the high activity and chemical/structural stability of the PtCo intermetallic nanoparticles and from the high degree of graphitization and well-defined porous structure of the bowl-like carbon support, which confers excellent electrical conductivity and oxygen transport properties. This study provides a reliable and universal strategy for the development of high-performance porous carbon supports for practical applications in fuel cells.

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Floatable S-scheme Bi2WO6/C3N4/carbon fiber cloth composite photocatalyst for efficient water decontamination Mingjie Cai, Yanping Liu, Kexin Dong, Xiaobo Chen, Shijie Li 2023, 52:  239-251.  DOI: 10.1016/S1872-2067(23)64496-1 Abstract ( 377 )   HTML ( 26 )   PDF (5196KB) ( 455 )   Supporting Information The development of easily recyclable and advanced photosystems is a promising strategy for achieving sustainable water decontamination in industrial applications. In this study, a flexible, floatable, and easily recyclable S-scheme photosystem of oxygen vacancy (OV)-rich Bi2WO6/C3N4/carbon fiber cloth (BWOV/CN/CF) was fabricated via sequential in situ growth of C3N4 and Bi2WO6 with oxygen vacancies on CF cloth. The integrated BWOV/CN/CF photosystem exhibited outstanding photocatalytic decontamination rates for TC (0.0353 min‒1) and Cr(VI) (0.0187 min−1), significantly exceeding CN/CF by 0.5 and 30.2 folds, respectively. This appreciable improvement is derived from the unique hierarchical S-scheme heterostructure with OV, which enables the enhanced capability of BWOV/CN/CF in light use and powerful photocarrier detachment, as well as offering abundant active centers. Significantly, the BWOV/CN/CF cloth shows intriguing industrial application prospects owing to its high anti-interference properties, broad pH applicability, good durability, easy recycling and operation, and extensive adaptability for diverse contaminant purification. Furthermore, the photocatalytic TC decomposition process, by-product biotoxicity, and photocatalysis mechanism were systematically evaluated. The ingenious design of floatable cloth-shaped photosystems offers an effective strategy for environmental purification.

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Theoretical screening of single-atom electrocatalysts of MXene-supported 3d-metals for efficient nitrogen reduction Jin-Nian Hu, Ling-Chan Tian, Haiyan Wang, Yang Meng, Jin-Xia Liang, Chun Zhu, Jun Li 2023, 52:  252-262.  DOI: 10.1016/S1872-2067(23)64501-2 Abstract ( 435 )   HTML ( 17 )   PDF (2558KB) ( 217 )   Supporting Information Single-atom catalysts (SACs) with metal atoms embedded in MXenes are potentially low-cost, highly efficient, and environment-friendly electrocatalysts for ammonia production due to their high stability, unique electronic structure, and the highest atom utilization. Here, density functional theory calculations are carried out to systematically investigate the geometries, stability, electronic properties of SACs with the 3d-transition metal M (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) atoms embedded in the Ti defect sites of Ti2CO2 (denoted as M1@Ti2CO2). A highly stable V1@Ti2CO2 catalyst has been found to show excellent catalytic performance for N2 reduction reaction to produce NH3 after screening the 3d transition metals. The results show that V1@Ti2CO2 can not only strongly adsorb N2, but also exhibits an excellent Nitrogen reduction reaction (NRR) catalytic activity with a limiting potential of only −0.20 V and a high ability to suppress the competing hydrogen evolution reaction. The excellent NRR catalytic activity of V1@Ti2CO2 is attributed to the strong covalent metal-support interaction that leads to superb N2 adsorption ability of V atom. Furthermore, the embedded V single atoms facilitate electron transfer, thus improving the catalytic performance for NRR. These results demonstrate that V1@Ti2CO2 is a potentially promising 2D material for building robust electrocatalyst for NRR.

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Theoretical insights into heteronuclear dual metals on non-metal doped graphene for nitrogen reduction reaction Ji Zhang, Aimin Yu, Chenghua Sun 2023, 52:  263-270.  DOI: 10.1016/S1872-2067(23)64500-0 Abstract ( 283 )   HTML ( 8 )   PDF (2560KB) ( 238 )   Supporting Information Electrochemical nitrogen reduction reaction (eNRR) is a promising strategy for sustainable ammonia production. To achieve high yield and energy efficiency, single-atom dispersion on nitrogen-doped graphene nanosheets has been extensively explored as an electrocatalyst for eNRR. However, challenges remain owing to the high overpotentials arising from unitary active sites and unabundant ligands. In this study, heteronuclear dual-metal catalysts with different non-metals doped in a graphene frame were computationally designed. After a two-step scanning based on density functional theory calculations, five candidates, namely FeMo-S, RuMo-B, RuMo-P, RuMo-S, and RuW-S, were identified as promising catalysts with calculated onset potentials of -0.18, -0.25, -0.27, -0.29, and -0.24 V, respectively. These catalysts can also effectively suppress the competitive hydrogen evolution reaction during NRR. Such excellent catalytic performance origins from two synergetic effects: (1) the cooperation of heteronuclear metals contribute to the electron transfer from active sites to the anti-bonding orbitals of N2 molecules adsorbed on catalysts to effectively activate N≡N bonds; (2) metal-ligands (non-metals) interactions moderate the binding strength of intermediates to slab, which is one of reasons for low NRR onset potential and high NH3 selectivity. The present study provides a theoretical understanding of the NRR mechanism of dual-metal catalysts, offering useful guidance for the rational design of catalysts with high selectivity and activity for NRR.

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Electronic effects of redox-active ligands on ruthenium-catalyzed water oxidation Jing Shi, Yu-Hua Guo, Fei Xie, Ming-Tian Zhang, Hong-Tao Zhang 2023, 52:  271-279.  DOI: 10.1016/S1872-2067(23)64497-3 Abstract ( 214 )   HTML ( 14 )   PDF (1521KB) ( 154 )   Supporting Information The process of water oxidation presents a significant challenge in the development of artificial photosynthetic systems. This complexity arises from the necessity of charge accumulation, involving four electrons and four protons, and O-O bond formation. The strategy of using redox-active ligands in conjunction with metals is recognized as an effective approach for managing this charge accumulation process, attracting considerable attention. However, the detailed mechanisms by which the electronic effect of the redox-active ligands affect the reactivity of the catalytic centers remain ambiguous. In this study, the electronic effect of a series of mononuclear Ru complexes furnished with redox-active ligands ([(LRN5‒)RuIII-OH]+, R = OMe, 3a; Me, 3b; H, 3c; F, 3d; CF3, 3e) was examined on water oxidation. A correlation was observed between redox potentials and substituent constants (σpara), indicating that different successive redox pairs are influenced by electron effects of varying intensities. Particularly, the ligand-centered oxidation (E {[(LN5-)+•RuIV=O]2+/[(LN5-)RuIV=O]+}) shows a greater dependence than the metal-centered PCET oxidations, E(RuIII-OH/RuII-OH2) and E(RuIV=O/RuIII-OH). The critical intermediate, [(LN5-)+•RuIV=O]2+, formed through ligand-centered oxidation, triggers O-O bond formation via its reaction with water. The rate constants of this crucial step can be effectively modulated by the substituents of the ligand. This study provides intricate insights into the role of the redox-active ligand in regulating the water oxidation process and further substantiates the effectiveness of the synergistic interaction of redox ligands and metals in controlling the multi-electron catalytic process.