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Chinese Journal of Catalysis
2022, Vol. 43, No. 12
Online: 18 December 2022

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Cover: Prof. Jintao Zhang and coworkers in their article on pages 3107–3115 reported the facile preparation of nitrogen and phosphorus co-doped three-dimensional porous carbon embedded with cobalt phosphide via the interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and the subsequent pyrolysis. The obtained electrocatalyst exhibited efficient electrocatalytic activities toward ORR, OER and HER.

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Editorial

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Preface to the special issue on electrocatalysis and electrosynthesis Yanguang Li, Yujie Sun 2022, 43 (12):  2937-2937.  DOI: 10.1016/S1872-2067(22)64182-2 Abstract ( 105 )   HTML ( 21 )   PDF (691KB) ( 104 )

Perspective

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Overcoming coke formation in high-temperature CO2 electrolysis Tongbao Wang, Guangtai Han, Ziyun Wang, Yuhang Wang 2022, 43 (12):  2938-2945.  DOI: 10.1016/S1872-2067(22)64120-2 Abstract ( 460 )   HTML ( 21 )   PDF (1346KB) ( 449 )   High-temperature CO2 reduction reaction (HT-CO2RR) in solid oxide electrochemical cells (SOECs) features near-unity selectivity, high energy efficiency, and industrial relevant current density for the production of CO, a widely-utilized “building block” in today’s chemical industry. Thus, it offers an intriguing and promising means to radically change the way of chemical manufacturing and achieve carbon neutrality using renewable energy sources, CO2, and water. Albeit with the great potential of HT-CO2RR, this carbon utilization approach, unfortunately, has been suffering coke formation that is seriously detrimental to its energy efficiency and operating lifetime. In recent years, much effort has been added to understanding the mechanism of coke formation, managing reaction conditions to mitigate coke formation, and devising coke-formation-free electrode materials. These investigations have substantially advanced the HT-CO2RR toward a practical industrial technology, but the resulting coke formation prevention strategies compromise activity and energy efficiency. Future research may target exploiting the control over both catalyst design and system design to gain selectivity, energy efficiency, and stability synchronously. Therefore, this perspective overviews the progress of research on coke formation in HT-CO2RR, and elaborates on possible future directions that may accelerate its practical implementation at a large scale.

Reviews

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Recent progress in electronic modulation of electrocatalysts for high-efficient polysulfide conversion of Li-S batteries Pan Zeng, Cheng Yuan, Genlin Liu, Jiechang Gao, Yanguang Li, Liang Zhang 2022, 43 (12):  2946-2965.  DOI: 10.1016/S1872-2067(21)63984-0 Abstract ( 262 )   HTML ( 13 )   PDF (13301KB) ( 273 )   With the merits of high energy density, environmental friendliness, and cost effectiveness, lithium-sulfur (Li-S) batteries are considered as one of the most promising next-generation electrochemical storage systems. However, the notorious polysulfide shuttle effect, which results in low active material utilization and serious capacity fading, severely impedes the practical application of Li-S batteries. Utilizing various electrocatalysts to improve the polysulfide redox kinetics has recently emerged as a promising strategy to address the shuttle effect. Specially, the electronic structure of the electrocatalysts plays a decisive role in determining the catalytic activity to facilitate the polysulfide conversion. Therefore, reasonably modulating the electronic structure of electrocatalysts is of paramount significance for improving the electrochemical performance of Li-S batteries. Herein, a comprehensive overview of the fascinating strategies to tailor the electronic structure of electrocatalysts for Li-S batteries is presented, including but not limited to vacancy engineering, heteroatom doping, single atom doping, band regulation, alloying, and heterostructure engineering. The future perspectives and challenges are also proposed for designing high-efficient electrocatalysts to construct high-energy-density and long-lifetime Li-S batteries.

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Recent advances in glycerol valorization via electrooxidation: Catalyst, mechanism and device Jianxiang Wu, Xuejing Yang, Ming Gong 2022, 43 (12):  2966-2986.  DOI: 10.1016/S1872-2067(22)64121-4 Abstract ( 1186 )   HTML ( 72 )   PDF (4713KB) ( 647 )   Glycerol is one of the most important biomass-based platform molecules, massively produced as a by-product in the biodiesel industry. Its high purification cost from the crude glycerol raw material limits its application and demands new strategies for valorization. Compared to the conventional thermocatalytic strategies, the electrocatalytic strategies can not only enable the selective conversion at mild conditions but also pair up the cathodic reactions for the co-production with higher efficiencies. In this review, we summarize the recent advances of catalyst designs and mechanistic understandings for the electrocatalytic glycerol oxidation (GOR), and aim to provide an overview of the GOR process and the intrinsic structural-activity correlation for inspiring future work in this field. The review is dissected into three sections. We will first introduce the recent efforts of designing more efficient and selective catalysts for GOR, especially toward the production of value-added products. Then, we will summarize the current understandings about the reaction network based on the ex-situ and in-situ spectroscopic studies as well as the theoretical works. Lastly, we will select some representative examples of creating real electrochemical devices for the valorization of glycerol. By summarizing these previous efforts, we will provide our vision of future directions in the field of GOR toward real applications.

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Theory-guided electrocatalyst engineering: From mechanism analysis to structural design Mingcheng Zhang, Kexin Zhang, Xuan Ai, Xiao Liang, Qi Zhang, Hui Chen, Xiaoxin Zou 2022, 43 (12):  2987-3018.  DOI: 10.1016/S1872-2067(22)64103-2 Abstract ( 1244 )   HTML ( 68 )   PDF (20984KB) ( 954 )   The exploitation of competent electrocatalysts is a key issue of the broad application of many promising electrochemical processes, including the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR), the CO2 reduction reaction (CO2RR) and the nitrogen reduction reaction (NRR). The traditional searches for good electrocatalysts rely on the trial-and-error approaches, which are typically tedious and inefficient. In the past decades, some fundamental principles, activity descriptors and catalytic mechanisms have been established to accelerate the discovery of advanced electrocatalysts. Hence, it is time to summarize these theory-related research advances that unravel the structure-performance relationships and enables predictive ability in electrocatalysis studies. In this review, we summarize some basic aspects of catalytic theories that are commonly used in the design of electrocatalysts (e.g., Sabatier principle, d-band theory, adsorption-energy scaling relation, activity descriptors) and their relevance. Then, we briefly introduced the fundamental mechanisms and central challenges of HER, OER, ORR, CO2RR and NRR electrocatalysts, and highlight the theory-based efforts used to address the challenges facing these electrocatalysis processes. Finally, we propose the key challenges and opportunities of theory-driven electrocatalysis on their future.

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Rational development of molecular earth-abundant metal complexes for electrocatalytic hydrogen production John Daniel McCool, Shiyuan Zhang, Inen Cheng, Xuan Zhao 2022, 43 (12):  3019-3045.  DOI: 10.1016/S1872-2067(22)64150-0 Abstract ( 73 )   HTML ( 6 )   PDF (1784KB) ( 87 )   For public health and environmental protection reasons, there is an urgent need to replace traditional fossil fuels with clean and renewable sources. Electrochemical splitting of water has the potential to produce clean hydrogen as a possible solution to global energy problems. This review article introduces the rational design of molecular metal complexes based on earth-abundant metals for electrocatalytic hydrogen production in water or water-organic media. Emphasis is placed on providing insight into structure-function relationships in catalytic properties for future ligand and catalyst design.

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Toward green syntheses of carboxylates: Considerations of mechanisms and reactions at the electrodes for electrocarboxylation of organohalides and alkenes Teera Chantarojsiri, Tassaneewan Soisuwan, Pornwimon Kongkiatkrai 2022, 43 (12):  3046-3061.  DOI: 10.1016/S1872-2067(22)64180-9 Abstract ( 74 )   HTML ( 3 )   PDF (2703KB) ( 112 )   Abstract: Electrosynthesis and carbon dioxide (CO2) utilization both have gained interest in recent years due to the efforts to alleviate the climate crisis. Significant progress in the field of electrochemical carboxylation using CO2 or electrocarboxylation of organic substrates, particularly organohalides and alkenes, has been made in the past decade. Different components of electrocarboxylation experimental setup as well as the understandings of the mechanism play an important role in the success of the carboxylate syntheses. In this review, overview of the proposed mechanisms and the electrochemical setup are described. The significance of electrochemical components, such as the effect of different cathodes, sacrificial anode materials, and other additives, are explained. The examples of electrocarboxylation for both organohalides and olefins are provided. Lastly, the current trends in the field and future directions are discussed.

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Rational design of bismuth-based catalysts for electrochemical CO2 reduction Bo Zhang, Yunzhen Wu, Panlong Zhai, Chen Wang, Licheng Sun, Jungang Hou 2022, 43 (12):  3062-3088.  DOI: 10.1016/S1872-2067(22)64132-9 Abstract ( 321 )   HTML ( 14 )   PDF (18202KB) ( 340 )   Sustainable conversion of carbon dioxide (CO2) to high value-added chemicals and fuels is a promising solution to solve the problem of excessive CO2 emissions and alleviate the shortage of fossil fuels, maintaining the balance of the carbon cycle in nature. The development of catalytic system is of great significance to improve the efficiency and selectivity for electrochemical CO2 conversion. In particular, bismuth (Bi) based catalysts are the most promising candidates, while confronting challenges. This review aims to elucidate the fundamental issues of efficient and stable Bi-based catalysts, constructing a bridge between the category, synthesis approach and electrochemical performance. In this review, the categories of Bi-based catalysts are firstly introduced, such as metals, alloys, single atoms, compounds and composites. Followed by the statement of the reliable and versatile synthetic approaches, the representative optimization strategies, such as morphology manipulation, defect engineering, component and heterostructure regulation, have been highlighted in the discussion, paving in-depth insight upon the design principles, reaction activity, selectivity and stability. Afterward, in situ characterization techniques will be discussed to illustrate the mechanisms of electrochemical CO2 conversion. In the end, the challenges and perspectives are also provided, promoting a systematic understanding in terms of the bottleneck and opportunities in the field of electrochemical CO2 conversion.

Communications

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Iron porphyrin with appended guanidyl group for significantly improved electrocatalytic carbon dioxide reduction activity and selectivity in aqueous solutions Hongbo Guo, Zuozhong Liang, Kai Guo, Haitao Lei, Yabo Wang, Wei Zhang, Rui Cao 2022, 43 (12):  3089-3094.  DOI: 10.1016/S1872-2067(21)63957-8 Abstract ( 105 )   HTML ( 3 )   PDF (1662KB) ( 72 )   Supporting Information Iron porphyrins have high activity and selectivity for electrocatalytic CO2 reduction reaction (CO2RR) in nonaqueous solutions, but they usually display poor or moderate selectivity for CO2RR in aqueous solutions because of the competitive hydrogen evolution reaction. Using water as the electrocatalytic reaction solvent is more favored because not only it is cheap, green and abundant but also it can sufficiently provide protons required for CO2RR. Therefore, developing Fe porphyrins as electrocatalysts for efficient and selective CO2RR in aqueous solutions is of both fundamental and practical significance. Herein, we report the design and synthesis of Fe porphyrin 1 with an appended guanidyl group and its electrocatalytic features for CO2RR in both nonaqueous and aqueous solutions. In acetonitrile, Fe porphyrin 1 and its guanidyl-free analogue, tetrakis(3,4,5-trimethoxyphenyl)porphyrin 2, are both efficient for electrocatalytic CO2-to-CO conversion, but the turnover frequency with 1 (3.9 × 105 s-1) is one order of magnitude larger than that with 2 (1.7 × 104 s-1), showing the critical role of the appended guanidyl group in improving electrocatalytic CO2RR activity. More importantly, in 0.1 mol L-1 KHCO3 aqueous solutions, 1 showed very high selectivity for electrocatalytic CO2-to-CO conversion with a Faradaic efficiency of 96%, while 2 displayed a Faradaic efficiency of 65% for the CO2-to-CO conversion. This work is of significance to show the effect of appended guanidyl group on improving both activity and selectivity of Fe porphyrins for CO2RR electrocatalysis.

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Unveiling subsurface hydrogen inhibition for promoting electrochemical transfer semihydrogenation of alkynes with water Qi Hao, Yongmeng Wu, Cuibo Liu, Yanmei Shi, Bin Zhang 2022, 43 (12):  3095-3100.  DOI: 10.1016/S1872-2067(22)64145-7 Abstract ( 94 )   HTML ( 7 )   PDF (2004KB) ( 95 )   Supporting Information Highly selective electrocatalytic semihydrogenation of alkynes to alkenes with water as the hydrogen source over palladium-based electrocatalysts is significant but remains a great challenge because of the excessive hydrogenation capacity of palladium. Here, we propose that an ideal palladium catalyst should possess weak alkene adsorption and inhibit subsurface hydrogen formation to stimulate the high selectivity of alkyne semihydrogenation. Therefore, sulfur-modified Pd nanowires (Pd-S NWs) are designedly prepared by a solid-solution interface sulfuration method with KSCN as the sulfur source. The introduction of S weakens the alkene adsorption and prevents the diffusion of active hydrogen (H*) into the Pd lattice to form unfavorable subsurface H*. As a result, electrocatalytic alkyne semihydrogenation is achieved over a Pd-S NWs cathode with wide substrate scopes, potential-independent up to 99% alkene selectivity, good fragile groups compatibility, and easily synthesized deuterated alkenes. An adsorbed hydrogen addition mechanism of this semihydrogenation reaction is proposed. Importantly, an easy modification of commercial Pd/C by in situ addition of SCN- enabling the gram-scale synthesis of an alkene with 99% selectivity and 95% conversion highlights the promising potential of our method.

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Guanine-regulated proton transfer enhances CO2-to-CH4 selectivity over copper electrode Jun Gong, Jinmeng Li, Chang Liu, Fengyuan Wei, Jinlong Yin, Wenzheng Li, Li Xiao, Gongwei Wang, Juntao Lu, Lin Zhuang 2022, 43 (12):  3101-3106.  DOI: 10.1016/S1872-2067(22)64113-5 Abstract ( 176 )   HTML ( 8 )   PDF (6282KB) ( 182 )   Supporting Information Electrocatalytic CO2 reduction has attracted growing attention as a promising route to realize artificial carbon recycling. Proton transfer plays an essential role in CO2 reduction and dramatically impacts product distribution. However, the precise control of proton transfer during CO2 reduction remains challenging. In this study, we present a well-controlled proton transfer through the modification of several purines with similar molecular structures, and reveal a direct correlation between surface proton transfer capability and CO2 reduction selectivity over Cu electrode. With a moderate proton transfer capability, the guanine modification can remarkably boost CH4 production and suppress C2 products formation. In-situ ATR-SEIRAS suggests a weakened *CO intermediate adsorption and a relatively low local pH environment after the guanine modification, which facilitates the *CO protonation and detachment for CH4 generation.

Articles

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In-situ formation of cobalt phosphide nanoparticles confined in three-dimensional porous carbon for high-performing zinc-air battery and water splitting Xinxin Shu, Maomao Yang, Miaomiao Liu, Huaisheng Wang, Jintao Zhang 2022, 43 (12):  3107-3115.  DOI: 10.1016/S1872-2067(21)64047-0 Abstract ( 171 )   HTML ( 9 )   PDF (3699KB) ( 120 )   Supporting Information The rational design of efficient and stable carbon-based electrocatalysts for oxygen reduction and oxygen evolution reactions is crucial for improving energy density and long-term stability of rechargeable zinc-air batteries (ZABs). Herein, a general and controllable synthesis method was developed to prepare three-dimensional (3D) porous carbon composites embedded with diverse metal phosphide nanocrystallites by interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and subsequent pyrolysis. Phytic acid as the dopant of polyaniline provides favorable anchoring sites for metal ions owing to the coordination interaction. Specifically, adjusting the concentration of adsorbed cobalt ions can achieve the phase regulation of transition metal phosphides. Thus, with abundant cobalt phosphide nanoparticles and nitrogen- and phosphorus-doping sites, the obtained carbon-based electrocatalysts exhibited efficient electrocatalytic activities toward oxygen reduction and evolution reactions. Consequently, the fabricated ZABs exhibited a high energy density, high power density of 368 mW cm‒2, and good cycling/mechanical stability, which could power water splitting for integrated device fabrication with high gas yields.

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Facet dependence of electrocatalytic furfural hydrogenation on palladium nanocrystals Wenbiao Zhang, Yanghao Shi, Yang Yang, Jingwen Tan, Qingsheng Gao 2022, 43 (12):  3116-3125.  DOI: 10.1016/S1872-2067(22)64097-X Abstract ( 124 )   HTML ( 5 )   PDF (3108KB) ( 124 )   Supporting Information Electrocatalytic hydrogenation (ECH) offers a sustainable route for the conversion of biomass-derived feedstocks under ambient conditions; however, an atomic-level understanding of the catalytic mechanism based on heterogeneous electrodes is lacking. To gain insights into the relation between electrocatalysis and the catalyst surface configuration, herein, the facet dependence of the ECH of furfural (FAL) is investigated on models of nanostructured Pd cubes, rhombic dodecahedrons, and octahedrons, which are predominantly enclosed by {100}, {110}, and {111} facets, respectively. The facet-dependent specific activity to afford furfuryl alcohol (FOL) follows the order of {111} > {100} > {110}. Experimental and theoretical kinetic analyses confirmed the occurrence of a competitive adsorption Langmuir-Hinshelwood mechanism on Pd, in which the ECH activity can be correlated with the difference between the binding energies of chemisorbed H (*H) and FAL (*FAL) based on density functional theoretical (DFT) calculations. Among the three facets, Pd{111} exhibiting the strongest *H but the weakest *FAL showed the copresence of the *H and *FAL intermediates on the Pd surface for subsequent hydrogenation, experimentally confirming its high ECH activity and Faradaic efficiency. The free energies determined using DFT calculations indicated that *H addition to the carbonyl of FAL on Pd{111} was thermodynamically preferred over desorption to gaseous H2, contributing to efficient ECH to afford FOL at the expense of H2 evolution. The obtained insights into the facet-dependent ECH underline that surface bindings assist ECH or H2 evolution considering their competitiveness. These findings are expected to deepen the fundamental understanding of electrochemical refinery and broaden the scope of electrocatalyst exploration.

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Density functional theory study of active sites and reaction mechanism of ORR on Pt surfaces under anhydrous conditions Guangdong Liu, Huiqiu Deng, Jeffrey Greeley, Zhenhua Zeng 2022, 43 (12):  3126-3133.  DOI: 10.1016/S1872-2067(22)64125-1 Abstract ( 132 )   HTML ( 4 )   PDF (2676KB) ( 138 )   Supporting Information Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells (PEMFCs) operated at a temperature > 100 °C. Here, by employing density functional theory calculations, we studied ORR on flat and stepped Pt(111) surfaces with both (110) and (100) type of steps. We found that, in contrast to ORR under hydrous conditions, (111) terrace sites are not active for ORR under anhydrous conditions, because of weakened binding of ORR intermediates induced by O* accumulation on the surface. On the other hand, step edges, which are generally not active for ORR under hydrous conditions, are predicted to be the active sites for ORR under anhydrous conditions. Among them, (110) type step edge with a unique configuration of accumulated O stabilizes O2 adsorption and facilitates O2 dissociation, which lead an overpotential < 0.4 V. To improve ORR catalysts in high-temperature PEMFCs, it is desirable to maximize (110) step edge sites that present between two (111) facets of nanoparticles.

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Efficient CO2 fixation with acetophenone on Ag-CeO2 electrocatalyst by a double activation strategy Anxiang Guan, Yueli Quan, Yangshen Chen, Zhengzheng Liu, Junbo Zhang, Miao Kan, Quan Zhang, Haoliang Huang, Linping Qian, Linjuan Zhang, Gengfeng Zheng 2022, 43 (12):  3134-3141.  DOI: 10.1016/S1872-2067(22)64116-0 Abstract ( 122 )   HTML ( 4 )   PDF (6182KB) ( 220 )   Supporting Information The electrocarboxylation reaction is an attractive means to convert CO2 into valuable chemicals under ambient conditions, while it still suffers from low efficiency due to the high stability of CO2. In this work, we report a double activation strategy for simultaneously activating CO2 and acetophenone by silver-doped CeO2 (Ag-CeO2) nanowires, featuring as an effective electrocatalyst for electrocarboxylation of acetophenone with CO2. Compared to the Ag foil, Ag nanoparticles and CeO2 nanowires, the Ag-CeO2 nanowire catalyst allowed to reduce the onset potential difference between CO2 and acetophenone activation, thus enabling efficient electrocarboxylation to form 2-phenyllactic acid. The Faradaic efficiency for producing 2-phenyllactic acid reached 91% at -1.8 V versus Ag/AgI. This double activation strategy of activating both CO2 and organic substrate molecules can benefit the catalyst design to improve activities and selectivities in upgrading CO2 fixation for higher-value electrocarboxylation.

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pH-Induced selective electrocatalytic hydrogenation of furfural on Cu electrodes Ling Zhou, Yingying Li, Yuxuan Lu, Shuangyin Wang, Yuqin Zou 2022, 43 (12):  3142-3153.  DOI: 10.1016/S1872-2067(22)64119-6 Abstract ( 238 )   HTML ( 12 )   PDF (3109KB) ( 202 )   Supporting Information The efficient and selective electrocatalytic hydrogenation (ECH) of furfural is considered a green strategy for achieving biomass-derived high-value chemicals. Regulating an aqueous electrolytic environment, a green hydrogen energy source of water, is significant for improving the selectivity of products and reducing energy consumption. In this study, we systematically investigated the mechanism of pH dependence of product selectivity in the ECH of furfural on Cu electrodes. Under acidic conditions, the oxygen atom dissociated directly from hydrogenated furfural-derived alkoxyl intermediates, followed by stepwise hydrogenation until H2O formation via a thermodynamically favorable proton-coupled electron transfer process, thereby inducing a high proportion of the hydrogenolysis product (2-methylfuran). However, under partial alkaline conditions, furfural could be directly hydrogenated to furfuryl alcohol (selectivity ~98%) due to the high-energy barrier of the deoxidation process via a surface hydride (Had) transfer. Our results highlight the vital role of the electrolytic environment in furfural selective conversion and broaden our fundamental understanding of hydrodeoxygenation reactions in ECH.

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Enhancing hydrogen electrocatalytic oxidation on Ni3N/MoO2 in-plane heterostructures in alkaline solution Lulu An, Shaofeng Deng, Xuyun Guo, Xupo Liu, Tonghui Zhao, Ke Chen, Ye Zhu, Yuxi Fu, Xu Zhao, Deli Wang 2022, 43 (12):  3154-3160.  DOI: 10.1016/S1872-2067(22)64126-3 Abstract ( 124 )   HTML ( 4 )   PDF (2917KB) ( 128 )   Supporting Information Nickel (Ni)-based materials act as one of the most promising candidates as platinum-group-metal-free (PGM-free) electrocatalysts for hydrogen oxidation reaction (HOR) in alkaline solution. Nevertheless, the electrocatalytic activity of pure Ni is significantly limited due to the sluggish kinetics under alkaline condition. To accelerate the kinetics, constructing heterostructures and nitride structures have been developed as two representative strategies. Here, we combined the two methods and presented a facile synthesis of the sheet-like Ni3N/MoO2 in-plane heterostructures for enhanced HOR in alkaline electrolytes. Relative to Ni or Ni3N, the Ni3N/MoO2 in-plane heterostructures exhibited a significantly increased mass activity by 8.6-fold or 4.4-fold, respectively. Mechanistic studies revealed that the enhanced activity of Ni3N/MoO2 could be attributed to the weakened hydrogen adsorption and strengthened hydroxyl adsorption. This work provides a facile approach to design high-efficiency catalysts for hydrogen-oxidation catalysis and beyond.

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Bismuth nanosheets with rich grain boundaries for efficient electroreduction of CO2 to formate under high pressures Sunhong Ruan, Biao Zhang, Jinhan Zou, Wanfu Zhong, Xiaoyang He, Jinhai Lu, Qinghong Zhang, Ye Wang, Shunji Xie 2022, 43 (12):  3161-3169.  DOI: 10.1016/S1872-2067(22)64131-7 Abstract ( 159 )   HTML ( 14 )   PDF (2308KB) ( 172 )   Supporting Information Electrochemical CO2 reduction reaction (CO2RR) driven by sustainable energy has emerged as an attractive route to achieve the target of carbon neutral. Formate is one of the most economically viable products, and electrocatalytic CO2RR to formate is a promising technology. High-pressure H-cell electrolyzer is easy to operate and allows high CO2 solubility for realizing high current density, but the design of highly efficient catalysts for working under high CO2 pressures remains challenging. Bismuth-based catalysts exhibit high formate selectivity, but suffer from limited activity. Here, we report a high-performance catalyst, which is derived from BiPO4 nanopolyhedrons during electrocatalytic CO2RR to formate in neutral solution under high CO2 pressures. A high partial current density of formate (534 mA cm-2) and formate formation rate (9.9 mmol h-1 cm-2) with a formate Faradaic efficiency of 90% have been achieved over BiPO4-derived catalyst at an applied potential of -0.81 V vs. RHE under 3.0 MPa CO2 pressure. We discover that BiPO4 nanopolyhedrons evolve into metallic Bi nanosheets with rich grain boundaries in electrocatalytic CO2RR under high CO2 pressures, and the grain boundaries of the BiPO4-derived catalyst play a vital role in promoting electrocatalytic CO2RR to formate. Our theoretical studies reveal that the charge redistribution occurs at the grain boundaries of Bi surface, and this promotes CO2 activation and increases HCOO* intermediate stability, thus making the pathway for CO2RR to formate more selective and energy-favorable. This work not only demonstrates a highly efficient catalyst for CO2RR to formate but also discovers a unique feature of catalyst evolution under high CO2 pressures.

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Mapping the kinetics of hydrogen evolution reaction on Ag via pseudo-single-crystal scanning electrochemical cell microscopy Yufei Wang, Mingyang Li, Emma Gordon, Hang Ren 2022, 43 (12):  3170-3176.  DOI: 10.1016/S1872-2067(22)64158-5 Abstract ( 77 )   HTML ( 5 )   PDF (3698KB) ( 183 )   Elucidating the structure-activity relationship in electrocatalysis is of fundamental interest for electrochemical energy conversion and storage. However, the heterogeneity in the surface structure of electrocatalysts, including the presence of various facets, poses an analytical challenge in revealing the true structure-activity relationship because the activity is conventionally measured on ensemble, resulting in an averaged activity that cannot be unequivocally associated with a single structural motif. Scanning electrochemical cell microscopy (SECCM) [1] combined with colocalized electron backscatter diffraction (EBSD) offers a direct way to reveal the correlative local electrochemical and structural information. Herein, we measured the hydrogen evolution reaction (HER) activity on Ag and its dependence on the crystal orientation. From the combined EBSD and SECCM mapping, it is found that Ag grains closer to {111} show a higher exchange current density, while those closer to {110} show a lower Tafel slope. The Tafel slope is also found to decrease with the step density increase. The ability to measure the electrocatalytic activity under a high mass-transfer rate allows us to reveal the activity difference at a high current density (up to 200 mA/cm2). The approach reported here can be expanded to other systems to reveal the nature of active sites of electrocatalysis

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Dual-site collaboration boosts electrochemical nitrogen reduction on Ru-S-C single-atom catalyst Liujing Yang, Chuanqi Cheng, Xun Zhang, Cheng Tang, Kun Du, Yuanyuan Yang, Shan-Cheng Shen, Shi-Long Xu, Peng-Fei Yin, Hai-Wei Liang, Tao Ling 2022, 43 (12):  3177-3186.  DOI: 10.1016/S1872-2067(22)64136-6 Abstract ( 214 )   HTML ( 11 )   PDF (5244KB) ( 277 )   Supporting Information Electrocatalytic reduction of nitrogen into ammonia (NH3) is a highly attractive but challenging route for NH3 production. We propose to realize a synergetic work of multi reaction sites to overcome the limitation of sustainable NH3 production. Herein, using ruthenium-sulfur-carbon (Ru-S-C) catalyst as a prototype, we show that the Ru/S dual-site cooperates to catalyse eletrocatalytic nitrogen reduction reaction (eNRR) at ambient conditions. With the combination of theoretical calculations, in situ Raman spectroscopy, and experimental observation, we demonstrate that such Ru/S dual-site cooperation greatly facilitates the activation and first protonation of N2 in the rate-determining step of eNRR. As a result, Ru-S-C catalyst exhibits significantly enhanced eNRR performance compared with the routine Ru-N-C catalyst via a single-site catalytic mechanism. We anticipate that our specifically designed dual-site collaborative catalytic mechanism will open up a new way to offers new opportunities for advancing sustainable NH3 production.

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Electrocatalytic hydrogen evolution from water at low overpotentials with cobalt complexes supported by redox-active bipyridyl-NHC donors Lizhu Chen, Xiaojun Su, Jonah W. Jurss 2022, 43 (12):  3187-3194.  DOI: 10.1016/S1872-2067(22)64151-2 Abstract ( 97 )   HTML ( 10 )   PDF (2025KB) ( 98 )   Three cobalt complexes bearing tunable, redox-active bipyridyl N-heterocyclic carbene (NHC)-based ligands have been studied for electrocatalytic hydrogen evolution from aqueous solutions. The effect of structural modifications to the ligand framework is investigated across the catalyst series, which includes a non-macrocyclic derivative (1-Co) and 16-(2-Co) and 15-(3-Co) membered macrocycles. A structure-activity relationship is demonstrated, in which the macrocyclic complexes have greater activity compared to their non-macrocyclic counterpart with the most rigid catalyst, supported by the 15-membered macrocycle, performing best overall. Indeed, 3-Co catalyzes H2 evolution from aqueous pH 4 acetate buffer with a Faradaic efficiency of 97% at a low overpotential of 330 mV. Mechanistic studies are consistent with formation of a cobalt-hydride species that is subsequently protonated to evolve H2 via a heterolytic pathway.