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Chinese Journal of Catalysis
2023, Vol. 50
Online: 18 July 2023

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Cover: Professor Liuyi Li and coworkers presented a systematic review of the research progress of covalent organic frameworks (COFs) for single-site photo- and electrocatalysis, including the COF structural features and design principles, modification strategies, characterization method, catalytic mechanisms, challenges and future perspectives, etc. Read more about the article behind the cover on page 45–82.

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Photocatalytic CO2 conversion: Beyond the earth Jingxiang Low, Chao Zhang, Ferdi Karadas, Yujie Xiong 2023, 50:  1-5.  DOI: 10.1016/S1872-2067(23)64472-9 Abstract ( 190 )   HTML ( 32 )   PDF (1233KB) ( 249 )   The issue of climate change attributed to CO2 emissions has led to increased attention towards the study and development of artificial photosynthesis through photocatalytic CO2 conversion to reconstruct the broken carbon cycle in nature. Photocatalytic CO2 conversion can simultaneously reduce the CO2 concentration in the atmosphere and produce valuable hydrocarbon fuels. With the recent discovery of abundant reserves of CO2 and water at extraterrestrial sites, it has been proposed that photocatalytic CO2 conversion can also be implemented at extraterrestrial sites to build up an artificial carbon cycle for providing propellants and life support for space missions. This comment presents our perspectives on the development of photocatalytic CO2 conversion beyond Earth, with a focus on its general principles and potential challenges that may arise at extraterrestrial sites. Finally, a brief overview of the future research directions in this field is presented.

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Recent advances in electrocatalytic ammonia synthesis Ling Ouyang, Jie Liang, Yongsong Luo, Dongdong Zheng, Shengjun Sun, Qian Liu, Mohamed S. Hamdy, Xuping Sun, Binwu Ying 2023, 50:  6-44.  DOI: 10.1016/S1872-2067(23)64464-X Abstract ( 2233 )   HTML ( 165 )   PDF (16652KB) ( 1665 )   Artificial electrocatalytic ammonia (NH3) synthesis is recently becoming a research hotspot. It can couple with clean renewable electricity, which is considered an energy-efficient and sustainable approach for regulating the recirculation of nitrogen species and meanwhile promoting the growth of a circular nitrogen economy. In this Account, we review recent advances in electrocatalytic ammonia synthesis. Firstly, we briefly introduce the research background and significance of three electrochemical NH3 synthesis routes: electrocatalytic nitrogen reduction, nitric oxide reduction, and nitrate/nitrite reduction. And then we give a detailed discussion of the latest research advances in electrocatalysts for ambient NH3 synthesis, mainly involving catalytic mechanisms, theoretical advances, and electrochemical performance. Finally, the existing challenges and future research needs for artificial electrosynthesis of NH3 are also highlighted.

Reviews

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Review of covalent organic frameworks for single-site photocatalysis and electrocatalysis Qing Niu, Linhua Mi, Wei Chen, Qiujun Li, Shenghong Zhong, Yan Yu, Liuyi Li 2023, 50:  45-82.  DOI: 10.1016/S1872-2067(23)64457-2 Abstract ( 905 )   HTML ( 58 )   PDF (26942KB) ( 712 )   Covalent organic frameworks (COFs) represent a burgeoning category of highly tunable crystalline porous materials, which have garnered significant attention as promising platforms for designing novel photo- and electrocatalysts. Single-site catalysis holds paramount importance in revealing the catalytic reaction mechanism and enhancing catalytic performance because of the maximum utilization of metal atoms and presence of a definite active center. Given the distinct advantages of single-site catalysts, such as single metal ions, single atoms, single active sites, and metal clusters, and COFs materials, there is a current surge of interest in using COFs materials as support materials to anchor highly dispersed single-sites. Consequently, the design and preparation of COF-based single-site catalysts have emerged as a prominent research topic in the fields of photo- and electrocatalysis, to address the pressing environmental and energy issues. This review provides an overview of the development of COF-based single-site photo- and electrocatalysts. Advanced applications of COF-based single-site photo- and electrocatalysts are comprehensively summarized and reviewed. Additionally, the review addresses the challenges faced by COF-based single-site photo- and electrocatalysts and discusses their future development trends. We aim to provide new insights into the application of COF-based single-site materials in photo- and electrocatalysis and further promote the development of catalytic science.

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Core/yolk-shell nanoreactors for tandem catalysis Meng Zhao, Jing Xu, Shuyan Song, Hongjie Zhang 2023, 50:  83-108.  DOI: 10.1016/S1872-2067(23)64463-8 Abstract ( 247 )   HTML ( 17 )   PDF (17742KB) ( 388 )   Tandem catalysis is of great significance in industrial production. Among various catalysts, the core/yolk-shell nanoreactors have been regarded as one of the most promising ones. Their special hierarchical structure is an excellent platform for the deposition of various active sites, thus bringing strong interaction reactions. More importantly, their well-controlled shell structures can prudentially select the filterable components onto the inner cores, which facilitates the operation of tandem reaction steps. In this review, we systematically summarize the state-of-art encouraging progress of the core/yolk-shell tandem nanoreactors. Apart from their unique characteristics and attractive advantages, we also explored the innovative synthetic approaches as well as the potential application fields. Meanwhile, the specific tandem catalytic mechanism was discussed in-depth. Finally, we outlined the challenges and opportunities of this field to propose some promising development directions.

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Electrocatalytic water splitting over perovskite oxide catalysts Yuannan Wang, Lina Wang, Kexin Zhang, Jingyao Xu, Qiannan Wu, Zhoubing Xie, Wei An, Xiao Liang, Xiaoxin Zou 2023, 50:  109-125.  DOI: 10.1016/S1872-2067(23)64452-3 Abstract ( 424 )   HTML ( 28 )   PDF (5404KB) ( 428 )   The urgent need for decarbonized hydrogen production to achieve carbon-neutral targets has highlighted the critical role of water electrolysis technology in advancing sustainability in various fields. However, the gap in economic efficiency between green hydrogen, generated by renewable electricity-driven water electrolysis, and gray hydrogen, generated by the consumption of fossil fuels, remains a challenge. Therefore, the exploration of cost-effective, active, and stable electrocatalysts toward water-splitting reactions is essential. Owing to their high-tolerance crystal structures, flexible elemental compositions, and adjustable electronic properties, perovskite oxides provide a vast material library for customizing next-generation electrocatalysts. Additionally, perovskite oxides are increasingly being developed into ideal model catalysts for unraveling scientific laws and theories, emphasizing the significance of investigating their important characteristics (e.g., structure-performance relationship, electronic property regulation, catalytic mechanism, and dynamic structural evolution). This review summarizes recent advances in perovskite oxides for water-splitting electrocatalysis, including their developmental history, compositional and structural diversities, structure-performance correlations, activity descriptors, catalytic mechanisms, and structural evolutions. We emphasize the importance of in situ characterization techniques for monitoring dynamic structural information and identifying important active species. Finally, we outline the opportunities and challenges of perovskite oxides for practical applications in water electrolysis, with the aim of providing further directions for exploring next-generation electrocatalysts.

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Metal-organic-framework-based materials as green catalysts for alcohol oxidation Guoqing An, Xiaowei Zhang, Canyang Zhang, Hongyi Gao, Siqi Liu, Geng Qin, Hui Qi, Jitti Kasemchainan, Jianwei Zhang, Ge Wang 2023, 50:  126-174.  DOI: 10.1016/S1872-2067(23)64451-1 Abstract ( 305 )   HTML ( 14 )   PDF (20125KB) ( 354 )   The selective oxidation of alcohols is widely regarded as one of the most important reactions in organic synthesis. Although efficient and environmentally friendly catalysts for alcohol oxidation are highly desirable, their development remains an enormous challenge. Metal-organic framework (MOF)-based catalysts have demonstrated great potential in the catalytic oxidation of alcohols and have remarkably progressed in the past few decades owing to their advantages of large surface area, tunable porous structure, abundant accessible active sites, and ease of reuse and recycling. In this review, recent representative results of the catalytic oxidation of alcohols by MOF-based materials are summarized and classified according to the type of material and reaction, such as pristine MOFs, MOF composites, and MOF derivatives for traditional thermal catalysis, photo-assisted catalysis, and electro-assisted catalysis. Each catalytic system is described in detail from multiple aspects, including the materials synthesis process, catalytic performance, alcohol oxidation mechanisms, and material stability. Thus, the aims of this review are to identify potentially efficient, green, and reusable MOF-based catalytic systems and to provide new insights for the further development of catalytic alcohol oxidation to obtain the target organics.

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Recent advances in photoredox catalytic transformations by using continuous-flow technology Xin Yuan, Hai-Bin Fan, Jie Liu, Long-Zhou Qin, Jian Wang, Xiu Duan, Jiang-Kai Qiu, Kai Guo 2023, 50:  175-194.  DOI: 10.1016/S1872-2067(23)64447-X Abstract ( 319 )   HTML ( 12 )   PDF (2352KB) ( 195 )   Photoredox catalysis is regarded as an economically appealing method for highly efficient and sustainable chemical syntheses. Nevertheless, numerous recent studies have revealed several unresolved disadvantages; for example, based on the Bouguer-Lambert-Beer law, the short propagation distance of photons in traditional batch reactors hampers the scalability of photocatalytic reactions. The introduction of continuous-flow technology for photochemical synthesis has resolved several of these problems. The use of photochemistry in microreactors has resulted in various transformations. Superior mixing ability, more effective heat transfer, and the easier magnification of continuous-flow chemical reactions are key to its success. Continuous-flow technology has allowed the optimization of several different types of conversion. Photoredox catalysts are effective under various reaction conditions because of their single-electron transfer properties. Common photocatalysts include transition metal complexes containing ruthenium, iridium, copper, iron, or manganese; organic photocatalysts; and heterogeneous photocatalysts. This review covers the types of photocatalysts that have recently been used in continuous-flow photochemistry.

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Non-noble metal single atom catalysts for electrochemical energy conversion reactions Sang Eon Jun, Sungkyun Choi, Jaehyun Kim, Ki Chang Kwon, Sun Hwa Park, Ho Won Jang 2023, 50:  195-214.  DOI: 10.1016/S1872-2067(23)64456-0 Abstract ( 231 )   HTML ( 16 )   PDF (14458KB) ( 555 )   Non-noble metal single atom catalysts (NNMSACs) are being pursued as economical alternatives to noble-metal SACs while retaining the high catalytic activity derived from the unique electronic structure of the single atomic sites. NNMSACs can serve crucial roles in various electrocatalytic reactions with high atomic utilization efficiency and selectivity comparable to noble metal SACs via adequate metal-support interactions. To this end, this review summarizes the characteristics of NNMSACs with regard to tuning reaction selectivity, metal-support interaction, and catalytic active center. Subsequently, an extensive summary of representative NNMSACs (Co, Ni, Fe, Cu, and dual metal SACs) is introduced for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). Finally, we present a brief conclusion and the remaining challenges for further advances of NNMSACs in geometric, electronic, and electrochemical properties.

Communications

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Photoredox deoxygenative allylation of carboxylic acids via selective 1,6-addition of acyl radicals to electron-deficient 1,3-dienes Lili Zhang, Yuhang Li, Zhenyu Guo, Yantao Li, Nian Li, Weipeng Li, Chengjian Zhu, Jin Xie 2023, 50:  215-221.  DOI: 10.1016/S1872-2067(23)64461-4 Abstract ( 316 )   HTML ( 15 )   PDF (982KB) ( 387 )   Supporting Information We report the 1,6-addition of acyl radicals to the electron-deficient 1,3-dienes under visible-light photoredox catalysis. The deoxygenative allylation of the carboxylic acid is achieved under mild conditions, generating the valuable 1,6-dicarbonyl compounds in moderate to good yields (up to 96%). A range of functionalized carboxylic acids are competent coupling partners. This deoxygenative allylation protocol has a high level of regio- and stereo-selectivity as well as good functional group comparability.

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Photocatalytic 1,3-dicarboxylation of unactivated alkenes with CO2 Han-Zhi Xiao, Bo Yu, Si-Shun Yan, Wei Zhang, Xi-Xi Li, Ying Bao, Shu-Ping Luo, Jian-Heng Ye, Da-Gang Yu 2023, 50:  222-228.  DOI: 10.1016/S1872-2067(23)64468-7 Abstract ( 254 )   HTML ( 12 )   PDF (1215KB) ( 328 )   Photocatalytic carboxylation with CO2 is a powerful strategy for the synthesis of functionalized carboxylic acids and their derivatives under mild conditions. However, the dicarboxylation of alkenes with CO2 is still underdeveloped and confined to the formation of only two C-C bonds. Herein, we report the 1,3-dicarboxylation of unactivated alkenes with CO2 via 1,2-aryl migration, which involves the cleavage of one C-C bond and the formation of three C-C bonds. This visible-light photocatalytic protocol is also distinguished by good functional group tolerance, broad substrate scope, and facile derivations of products to heterocyclic scaffolds. Mechanistic studies indicate that the in situ generated formate could act as the radical precursor of CO2˙ˉ, and the following radical addition, 1,2-aryl migration, single electron reduction, and nucleophilic attack at the second CO2 would afford the dicarboxylic acids.

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Deep learning guided enzyme engineering of Thermobifida fusca cutinase for increased PET depolymerization Shuaiqi Meng, Zhongyu Li, Peng Zhang, Francisca Contreras, Yu Ji, Ulrich Schwaneberg 2023, 50:  229-238.  DOI: 10.1016/S1872-2067(23)64470-5 Abstract ( 233 )   HTML ( 17 )   PDF (14996KB) ( 296 )   Supporting Information A responsible and sustainable circular economy of polymers requires efficient recycling processes with a low CO2 footprint. Enzymatic depolymerization of polyethylene terephthalate (PET) is a first step to make PET polymers a part of a circular economy of polymers. In this study, a structure-based deep learning model was utilized to identify residues in TfCut2 that are responsible for improved hydrolytic activity and enhanced stability. Machine learning guided design identified novel beneficial positions (L32E, S35E, H77Y, R110L, S113E, T237Q, R245Q, and E253H), which were evaluated and stepwise recombined yielding finally the beneficial variant L32E/S113E/T237Q. The latter TfCut2 variant exhibited improved PET depolymerization when compared with TfCut2 WT (amorphous PET film, 2.9-fold improvement // crystalline PET powder (crystallinity > 40%), 5.3-fold improvement). In terms of thermal resistance the variant L32E/S113E/T237Q showed a 5.7 °C increased half-inactivation temperature (T5060). The PET-hydrolysis process was monitored via a quartz crystal microbalance with dissipation monitoring (QCM-D) in real-time to determine depolymerization kinetics of PET coated onto the gold sensor. Finally, conformational dynamics analysis revealed that the substitutions induced a conformational change in the variant L32E/S113E/T237Q, in which the dominant conformation enabled a closer contact between the catalytic site and PET resulting in increased PET-hydrolysis. Overall, this study demonstrates the potential of deep learning models in protein engineering for identifying and designing efficient PET depolymerization enzymes.

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1D S-scheme heterojunction of urchin-like SiC-W18O49 for enhancing photocatalytic CO2 reduction Min Lin, Meilan Luo, Yongzhi Liu, Jinni Shen, Jinlin Long, Zizhong Zhang 2023, 50:  239-248.  DOI: 10.1016/S1872-2067(23)64477-8 Abstract ( 148 )   HTML ( 7 )   PDF (2759KB) ( 247 )   Supporting Information Constructing heterojunction is an important method to improve the performance of photocatalyst for CO2 reduction. In this work, W18O49 nanosheets (NSs) were grown on the surface of SiC nanocages (NCs) to form the sea urchin ball morphology by solvothermal method. The SiC-W18O49 composite photocatalyst processes 1D S-scheme heterojunction electron transport pathway. The special urchin morphology provides a large surface area for the contact between photocatalyst and CO2 reactants. Meantime, the S-scheme internal electric field at the heterogeneous interface of SiC-W18O49 composite photocatalyst can effectively promote the separation and migration of photogenerated carrier pairs owing to 1D heterojunction structure. The photocatalytic CO2 reduction products (CO + CH4 + CH3OH) can be produced up to 21.87 μmol g-1 h-1 by SiC-W18O49 composite photocatalyst, which was 3.38 and 3.71 times of the total reduction activity of the parent SiC and W18O49, respectively. This work will provide a new idea for the design of heterojunction morphology and structure for boosting photocatalytic CO2 reduction.

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A computational study of electrochemical CO2 reduction to formic acid on metal-doped SnO2 Zhaochun Liu, Xue Zong, Dionisios G. Vlachos, Ivo A. W. Filot, Emiel J. M. Hensen 2023, 50:  249-259.  DOI: 10.1016/S1872-2067(23)64476-6 Abstract ( 235 )   HTML ( 14 )   PDF (2745KB) ( 270 )   Supporting Information Electrochemical reduction of CO2 to formic acid (HCOOH) can contribute to the renewable energy transition as a liquid carrier of renewably hydrogen. Here, we investigated the catalytic requirements of SnO2 electrodes for efficient CO2 reduction to HCOOH using density functional theory and microkinetics simulations. Hydroxylation of the surface is a prerequisite to achieve a high activity with predicted current densities in agreement with experiment. The resulting surface is selective to HCOOH production with a negligible contribution of the hydrogen evolution reaction. Mechanistically, it is found that the reaction proceeds via hydrogenation of adsorbed CO2 to carboxylate (COOH), which is then further hydrogenated to the desired product. Doping of the surface by commonly used elements (Bi, Pd, Ni and Cu) identifies Bi as the preferred promoter to substantially improve the current density. Brønsted-Evans-Polanyi relations are established for the two key steps in the mechanism. Overall, carboxylate formation is the rate-controlling step. The CO2 reduction activity is analyzed in terms of two descriptors, namely the free energies for the two protonation steps, showing that Bi presents the highest activity.

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Acid-durable intermetallic CaNi2Si2 catalyst with electron-rich Ni sites for aqueous phase hydrogenation of unsaturated organic anhydrides/acids Shiyao Liu, Yutong Gong, Xiao Yang, Nannan Zhang, Huibin Liu, Changhai Liang, Xiao Chen 2023, 50:  260-272.  DOI: 10.1016/S1872-2067(23)64473-0 Abstract ( 201 )   HTML ( 7 )   PDF (9273KB) ( 186 )   Supporting Information The study of the aqueous-phase selective hydrogenation of maleic anhydride to succinic acid is important for expanding the coal chemical industry chain and promoting biomass conversion. The key lies in the development of highly efficient and stable non-noble metal catalysts. Herein, we report a novel intermetallic CaNi2Si2 catalyst with high activity and stability for the aqueous-phase selective hydrogenation of maleic anhydride. The results from the experiments and theoretical calculations demonstrated that the high catalytic performance was due to the synergy of the electron-rich Ni active sites, enhanced adsorption of C=C bonds, and favorable activation of H2. The yield of succinic acid can be 100% over the CaNi2Si2 catalyst at the contact time of 5.4 gcat/(mmolreactant·min-1) under 3 MPa and 120 °C in the continuous flow reactor. Furthermore, the special coordination environment and electronic structure of Ni in CaNi2Si2 inhibit the formation of carboxylates, thus enhancing the acid resistance in the reaction environment. The fine design and regulation of the structure of intermetallic silicides will be important references for the controllable optimization of maleic anhydride hydrogenation catalysts and provide new insights into the development of efficient and stable selective hydrogenation catalysts in harsh reaction environments.

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Dual co-catalysts Ag/Ti3C2/TiO2 hierarchical flower-like microspheres with enhanced photocatalytic H2-production activity Defa Liu, Bin Sun, Shuojie Bai, Tingting Gao, Guowei Zhou 2023, 50:  273-283.  DOI: 10.1016/S1872-2067(23)64462-6 Abstract ( 299 )   HTML ( 25 )   PDF (11933KB) ( 422 )   Supporting Information Solar-powered semiconductor photocatalysis is considered a powerful strategy for addressing environmental pollution and energy crisis. Nevertheless, the separation and transfer abilities of photogenerated photocatalysts remain unsatisfactory. Herein, dual Ti3C2 nanosheets/Ag co-catalysts synergistically decorated hierarchical flower-like TiO2 microspheres for boosting photocatalytic H2 production were fabricated by electrostatic self-assembly and subsequent photoreduction procedures. The optimal Ag/Ti3C2/TiO2 composite demonstrated an excellent photocatalytic H2-production rate of 1024.72 μmol g-1 h-1 under simulated solar irradiation, achieving nearly 40, 2.3, and 1.8 folds with respect to that obtained on pristine TiO2, optimized Ti3C2/TiO2 composite, and Ag/TiO2 composite, respectively. The considerably improved photocatalytic H2-production activity is associated with the synergistic effect of the hierarchical flower-like structure of TiO2, excellent electrical conductivity of Ti3C2, and surface plasmon resonance effect of Ag, which enhances the light absorption capacity and promotes the separation and transfer of photogenerated carriers. This study provides insight into the design of high-efficiency photocatalysts with dual co-catalysts for solar H2 production.

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Fine-structure sensitive deep learning framework for predicting catalytic properties with high precision Yuzhuo Chen, Hao Wang, Bing Lu, Ni Yi, Liang Cao, Yong Wang, Shanjun Mao 2023, 50:  284-296.  DOI: 10.1016/S1872-2067(23)64467-5 Abstract ( 248 )   HTML ( 13 )   PDF (3684KB) ( 266 )   Supporting Information The fine structure of a surface considerably affects its catalytic performance in structurally sensitive reactions. High-throughput (HT) screening and machine learning (ML) are considered efficient for exploring the hidden rules of impacts. However, no protocol for constructing an interpretable ML framework sensitive to fine structures has been reported thus far. Herein, we developed a data augmented convolutional neural network (CNN)-based ML framework called "global + local" convolutional neural network (GLCNN), which combines "global + local" features. This framework captures original fine structures without the use of complicated encoding methods by transforming the catalytic surfaces and adsorption sites into two-dimensional grids and one-dimensional descriptors, respectively. The GLCNN framework accurately predicted and distinguished the adsorption energies of OH on a set of analogous carbon-based transition-metal single-atom catalysts with a mean absolute error of less than 0.1 eV. Moreover, this model yields the best results among popular models trained on large datasets so far. Unlike conventional CNN and descriptor-based models with one-sided feature extraction, this fine-structure-sensitive ML framework can extract key factors that affect the catalytic performance from both geometric and chemical/electronic features, such as symmetry and coordination elements, through unbiased interpretable analysis. This framework provides a feasible solution for the high-precision HT screening of heterogeneous catalysts with a broad physical and chemical space.

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Highly dispersed Pt boosts active FexN formation in ammonia decomposition Keshia Saradima Indriadi, Peijie Han, Shipeng Ding, Bingqing Yao, Shinya Furukawa, Qian He, Ning Yan 2023, 50:  297-305.  DOI: 10.1016/S1872-2067(23)64465-1 Abstract ( 188 )   HTML ( 9 )   PDF (5235KB) ( 280 )   Supporting Information Ammonia decomposition plays an important role in hydrogen production, especially in the context of a hydrogen economy. Fe-based catalysts are a popular choice due to their affordability and moderate activity, making them attractive for large-scale applications. However, the transformation of Fe-based catalysts into more active FexN species can be slow, resulting in a prolonged induction period. To address this issue, we investigated the effects of Pt addition on FexN formation in ammonia decomposition. Our results show that even a slight Pt addition significantly enhances the FexN formation rate, increasing it over threefold. Pt aids in H2 desorption via reverse spillover, which, in turn, exposes more Fe surface sites where nitridation occurs, leading to the formation of iron nitride. Characterization via High-angle annular dark-field imaging scanning transmission electron microscopy, X-ray diffraction, and in situ X-ray absorption spectroscopy (XAS) revealed the formation of Fe2N as active species, whereas temperature-programmed hydrogen desorption, temperature-programmed reduction by hydrogen, and in situ XAS supported the existence of H reverse spillover and spillover effects. Overall, our study provides an improved understanding of the active species formation mechanism of Fe catalysts in ammonia decomposition and offers a simple strategy for improving their catalytic performance.

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Bimetallic single-cluster catalysts anchored on graphdiyne for alkaline hydrogen evolution reaction Bin Chen, Ya-Fei Jiang, Hai Xiao, Jun Li 2023, 50:  306-313.  DOI: 10.1016/S1872-2067(23)64459-6 Abstract ( 479 )   HTML ( 29 )   PDF (2177KB) ( 353 )   Supporting Information Pt-based electrocatalysts suffer from high water dissociation barriers that limit their overall hydrogen evolution reaction (HER) activities in alkaline media. Here we predict the bimetallic four-atom single-cluster catalysts (SCCs) M1A3 (M as later transition metal and A as early transition metal) with pyramidal structure supported on graphdiyne (GDY) for alkaline HER. Theoretical calculations show that the stable Pt1Ti3/GDY SCC delivers high alkaline HER activity via the Volmer-Heyrovsky mechanism. The excellent catalytic performance of Pt1Ti3/GDY SCC is attributed to both the low-valent Pt site that renders an optimal hydrogen adsorption free energy (ΔG*H), and the synergic effect of adjacent Ti sites that leads to a low water dissociation barrier. By screening alternative M1 in M1Ti3/GDY for optimal ΔG*H and facile water dissociation, we further identify the Ir1Ti3/GDY SCC to be a potentially high-performing alkaline HER electrocatalyst at low *OH coverage. Our work provides new insights and guidelines for the rational design of alkaline HER electrocatalysts.

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Interface engineering of a GaN/In2O3 heterostructure for highly efficient electrocatalytic CO2 reduction to formate Xuan Li, Xingxing Jiang, Yan Kong, Jianju Sun, Qi Hu, Xiaoyan Chai, Hengpan Yang, Chuanxin He 2023, 50:  314-323.  DOI: 10.1016/S1872-2067(23)64455-9 Abstract ( 240 )   HTML ( 13 )   PDF (4832KB) ( 230 )   Supporting Information Electrocatalytic CO2 reduction reaction (eCO2RR) to obtain formate is a promising method to consume CO2 and alleviate the energy crisis. Indium-based electrocatalysts have demonstrated considerable potential to produce formate. However, their unsatisfactory long-term stability and selectivity restrict their widespread application. In this study, a heterostructure of GaN- and In2O3-encapsulated porous carbon nanofibers was constructed via electrospinning and the phase transition of eutectic gallium-indium during calcination. The GaN and In2O3 nanoparticle-encapsulated porous carbon nanofibers, when used as electrocatalysts for eCO2RR, displayed high formate selectivity with a faradaic efficiency of 87% and maximum partial current density of 29.7 mA cm-2 in a 0.5 mol L-1 KHCO3 aqueous solution. The existence of the interface can cause a positive shift in the In 3d binding energy, leading to electronic redistribution. Moreover, the GaN component induced a higher proportion of O-vacancy sites in the In2O3 phase, resulting in improved selectivity for CO2-to-formate. In-situ Raman experiments and density functional theory calculations revealed that the interface between GaN and In2O3 could lower the adsorption energy of the key intermediates for formate production, thus providing superior eCO2RR performance. In addition, the framework of the porous carbon nanofibers exhibited a large electrochemically active surface area, which enabled the full exposure of the active sites. This study highlights the cooperation between GaN and In2O3 components and provides new insights into the rational design of catalysts with high CO2-to-formate conversion efficiencies.

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Defect-rich Cu@CuTCNQ composites for enhanced electrocatalytic nitrate reduction to ammonia Na Zhou, Jiazhi Wang, Ning Zhang, Zhi Wang, Hengguo Wang, Gang Huang, Di Bao, Haixia Zhong, Xinbo Zhang 2023, 50:  324-333.  DOI: 10.1016/S1872-2067(23)64454-7 Abstract ( 398 )   HTML ( 21 )   PDF (5898KB) ( 401 )   Supporting Information Electrochemical conversion of nitrate (NO3‒) pollutants into chemical feedstock and fuel ammonia (NH3) can contribute to sustainable mitigation of the current severe energy and environmental crises. However, the electrocatalytic NO3‒ reduction to NH3 (NRA) involves a sluggish multielectron and proton transfer process that competes with the hydrogen evolution reaction (HER) in aqueous media, imposing great challenges in developing highly selective catalysts for NRA. In this study, we developed a copper and copper-tetracyanoquinodimethane composite catalyst (Cu@CuTCNQ), which possesses a high density of copper vacancy defects. This catalyst has been proven to be efficient for NRA through an in situ electrochemical reconstruction method. The structural evolution of CuTCNQ during NRA was investigated by in situ Raman spectroscopy, which indicated an accelerated charge transfer from the CuTCNQ substrate to the derived Cu, which facilitated the adsorption activation of NO3‒. The obtained Cu@CuTCNQ exhibited an excellent catalytic performance for NRA, with a Faradaic efficiency of 96.4% and productivity of 144.8 μmol h-1 cm-2 at -0.6 V vs. a reversible hydrogen electrode, superior to Cu nanoparticle counterparts and most Cu-based catalysts. Cu vacancy defects and sufficient interfacial charge transfer synergistically optimize the charge distribution of Cu active sites, reduce the energy barrier for NO3‒ adsorption, and promote deoxidation and hydrogenation processes, thus enhancing NRA and selectivity.

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Revealing the electrocatalytic mechanism of layered crystalline CoMoO4 for water splitting: A theoretical study from facet selecting to active site engineering Shipeng Geng, Liming Chen, Haixin Chen, Yi Wang, Zhao-Bin Ding, Dandan Cai, Shuqin Song 2023, 50:  334-342.  DOI: 10.1016/S1872-2067(23)64458-4 Abstract ( 335 )   HTML ( 21 )   PDF (3667KB) ( 314 )   Supporting Information Deciphering the atomic-level properties and mechanism of electrocatalysts for water splitting is vital for the development of highly active non-noble-metal catalysts. Herein, we conduct a detailed study of layered crystalline CoMoO4 using density functional theory (DFT) calculations. The layered arrangement of CoMoO4 along the [110] lattice direction is observed, and the two thermodynamically stable and most exposed (110)A and (001)A crystal facets are selected among all low-index facets by surface energy calculations and Wulff construction to study the electrocatalytic activity for alkaline water splitting and corresponding mechanism. CoMoO4 with an exposed (110)A facet (i.e., CMO (110)A) exhibited a high hydrogen evolution reaction (HER) activity, with a ΔGH* of 0.22 eV, which is similar to that of Pt because the adsorbed H is allowed to interact with two oxygen atoms (O3 and Oadj). The (110)A facet also possesses better H2O adsorption and dissociation abilities than the (001)A facet, benefiting the HER performance in alkaline solutions. Moreover, the overpotential of the (110)A facet for the electrocatalytic oxygen evolution reaction (OER) is only 0.74 V according to the Gibbs free-energy calculation, this overpotential is lower than that of the (001)A facet (0.84 V) owing to the stronger binding and more stable adsorption states between Co and O for the intermediate *O. By allowing us to identify highly active facets and sites, this approach guided the selective synthesis of CoMoO4 and its isostructural substances, such as Mn(Ni, Fe)MoO4 nanocatalysts, for alkaline water splitting.

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Highly selective photoreduction of CO2 catalyzed by the encapsulated heterometallic-substituted polyoxometalate into a photo-responsive metal-organic framework Huijie Li, Manzhou Chi, Xing Xin, Ruijie Wang, Tianfu Liu, Hongjin Lv, Guo-Yu Yang 2023, 50:  343-351.  DOI: 10.1016/S1872-2067(23)64453-5 Abstract ( 247 )   HTML ( 10 )   PDF (9577KB) ( 362 )   Supporting Information The highly selective photoreduction of CO2 into valuable chemical fuels such as CO has been considered as an effective strategy to address modern energy and environmental issues. In this work, we have adopted the well-established impregnation approach to construct a P2W15Ni3{Re(CO)3}3 @NU-1000 composite by incorporating heterometallic-substituted P2W15Ni3{Re(CO)3}3 polyoxometalate (POM) into the pores of metal-organic framework (NU-1000) host. Upon light irradiation, the resulting P2W15Ni3{Re(CO)3}3@NU-1000 composite can effectively photocatalyze CO2 reduction, obtaining a CO production of 28982 μmol g-1 with 93.5% selectivity during 10-h photocatalysis. The catalytic system exhibits great long-term recyclability and stability for at least four successive recycles. The proposed photocatalytic mechanism was confirmed by a series of photochemical and spectroscopic analyses.

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Reshaping the coordination and electronic structure of single atom sites on the right branch of ORR volcano plot Liyuan Gong, Ying Wang, Jie Liu, Xian Wang, Yang Li, Shuai Hou, Zhijian Wu, Zhao Jin, Changpeng Liu, Wei Xing, Junjie Ge 2023, 50:  352-360.  DOI: 10.1016/S1872-2067(23)64460-2 Abstract ( 199 )   HTML ( 3 )   PDF (3391KB) ( 195 )   Supporting Information The coordination environment of atomic metal sites in single atom catalysts is of vital significance in tailoring the d-orbital states and thus the catalytic behavior towards oxygen reduction reaction (ORR), thereby offering great promise to boost activity via regulating the local chelation structure. Herein we designed a carbon coordination environment for the atomic M sites reside on the right leg of the volcano plot, to effectively counter balance the low adsorption energy of the metal center to oxygen species. Combining time-of-flight secondary ion mass spectrometry and density functional theory calculations, we unveiled the M-C coordination structure and the thus induced changes in electronic structure and ORR catalytic behavior. The reshape in coordination structure, i.e., the replacement of typical nitrogen coordination by low electronegativity carbon coordination, gives rise to exceptional intrinsic activity towards ORR. This work brings a new perspective to boost the activity of single atom catalysts on the weak bonding leg, with exceptional ORR activity being further expected through advancing the chelation structure.

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Infiltration of C-ring into crystalline carbon nitride S-scheme homojunction for photocatalytic hydrogen evolution Zhihan Yu, Chen Guan, Xiaoyang Yue, Quanjun Xiang 2023, 50:  361-371.  DOI: 10.1016/S1872-2067(23)64448-1 Abstract ( 238 )   HTML ( 7 )   PDF (3219KB) ( 237 )   Supporting Information Enhancing the carrier separation in graphitized carbon nitride (g-C3N4) is advantageous for improving its photocatalytic activity. Herein, we propose a feasible method for preparing CN-C by thermal polymerization to gradually infiltrate carbon rings (C-rings) into the surface of crystalline carbon nitride (CN), enabling photogenerated electrons to be transferred rapidly between the CN inner layers and the CN/C outer layer. Successful penetration and distribution of carbon rings into carbon nitride were confirmed by secondary ion mass spectroscopy using ratio analysis of C and N elements at various depths of the prepared photocatalyst. Theoretical calculations indicated that CN and CN/C in the molecule generated different Fermi levels to form an S-scheme homojunction, establishing appropriate built-in electric fields and thus enabling interlayer charge migration. Moreover, the overlap of the conjugate plane of C-rings with carbon nitride led to the formation of photogenerated in-plane charge transfer tunnels. The two-electron transfer tunnels greatly improved the dissociation efficiency of photogenerated electrons. The prepared sample loaded with 3 wt% Pt as a co-catalyst for hydrogen production under visible light irradiation, and the prepared optimal sample CN-C showed a maximum quantum efficiency of 15.56% for photocatalytic H2 evolution at 385 nm. This research introduces a new idea for constructing a directional transfer path for charge carriers in-plane and intralayer.

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Enhanced dehydrogenation kinetics for ascorbic acid electrooxidation with ultra-low cell voltage and large current density Bo Zhou, Jianqiao Shi, Yimin Jiang, Lei Xiao, Yuxuan Lu, Fan Dong, Chen Chen, Tehua Wang, Shuangyin Wang, Yuqin Zou 2023, 50:  372-380.  DOI: 10.1016/S1872-2067(23)64446-8 Abstract ( 224 )   HTML ( 6 )   PDF (8059KB) ( 241 )   Supporting Information Dehydroascorbic acid (DHA) production from ascorbic acid electrochemical oxidation (AAOR) can be used to upgrade biomass derivatives and hydrogen production with low energy consumption. Carbon materials are a promising class of nonmetal AAOR electrocatalysts; however, their performance does not meet the requirements for practical applications. In this study, an oxygen-containing group (OCG)-modified carbon electrocatalyst was prepared via oxygen plasma treatment. It could drive a current density of 100 mA cm-2 at only 0.65 VRHE and realize a Faradaic efficiency of over 90% for DHA production with long-term stability of 20 h. A proton exchange membrane-type electrolyzer integrating the anodic AAOR and the cathodic hydrogen evolution reaction (HER) was assessed. It only requires a cell voltage input of 0.98 V to deliver a current density of 1000 mA cm-2, which is superior to most reported organic upgrading reactions. Moreover, it only needs 1.54 kWh to produce normal cubic H2, which is one-third of that of traditional water electrolysis. Importantly, the contribution of each type of OCG was investigated by combining electrochemical measurements and theoretical calculations. It was revealed that the OCGs, especially the carboxyl groups (-COOH) of carbon materials, could enhance the dehydrogenation kinetics of the AAOR, thereby boosting the electrocatalytic activity. This study presents a low-energy and eco-friendly strategy for electrochemical biomass upgrading and hydrogen production, provides an in-depth understanding of the role of oxygen-containing functional groups in the AAOR, and guides the design of carbon-based electrocatalysts for AAOR.