Nickel single-atom catalysts (Ni SACs) hold great promise for the electrochemical CO2 reduction reaction (CO2RR) to CO. However, there remains a lack of synthetic strategies for achieving high CO2RR performance in a zero-gap electrolyzer. Herein, we demonstrate asymmetrically coordinated Ni SACs and membrane electrode assembly (MEA) structures to achieve outstanding CO2RR performance in a zero-gap electrolyzer. N, S-coordinated Ni SAC with the Ni-N3S1 structure (Ni-NSC-1) showed a higher Faradaic efficiency (FECO) and partial current density (jCO) of CO than N-coordinated Ni SACs (Ni-NCs). This was due to the coordination environment of Ni and increased N and S content in the carbon support. The FECO, jCO, and stability of the Ni-NSC-1 were further improved by modulating the MEA structure and operating temperature. As a result, a maximum FECO of 92.85% (at 2.1 V) and jCO of 286.54 mA/cm2 (at 2.3 V) were achieved using a Sustainion X37-50 GT membrane at 343 K. Moreover, the Ni-NSC-1 with Sustainion X3750 GT exhibited long-term stability for over 60 h, maintaining a high FECO of 95% at 100 mA/cm2. (c) 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The introduction of a porous structure is a promising approach to promote the electrochemical reaction of catalysts, which can maximize the utilization of catalytic active sites and enhance mass transport. To fully un-derstand the role of the porous structure, parallel studies on both half-cell and full-cell environments must be performed; however, few studies have reported electrochemical CO2 conversion in a full-cell operation. In this work, we fabricated four types of porous Ni-N-C model catalysts designed to systematically investigate the relationship between porous structures and catalytic performances in a membrane electrode assembly (MEA) based catholyte-free CO2 electrolyzer. The performance degradation of the microporous catalyst in the MEA resulted from low CO2 accessibility due to small openings (<2 nm), and the absence of meso-or macropores that can facilitate mass transport in the catalyst layer. A thick catalyst layer developed a region in which H2 evolution was dominant; the formation of this region degraded the CO2 reduction efficiency in the MEA based on the macroporous catalyst. Consequently, mesoporous Ni-Nx catalysts with small, uniform particles exhibited the highest efficiency in MEAs, because their appropriate pore size and catalyst layer thickness facilitated mass transport. The optimized catalyst achieved industry-relevant performance for CO production (265 mA cm-2 at 2.3 V) with a state-of-the-art energy efficiency of 55 % and excellent long-term stability in a full cell.

Electrochemical reduction of CO2 to various chemicals is a promising approach to dealing with excessive CO2 accumulation in the atmosphere. Even though numerous electrocatalysts have been extensively utilized for the reaction, several challenges remain such as high overpotential, poor stability, and low selectivity followed by the domination of hydrogen formation. To overcome these problems, multi-component materials have been pro-posed due to their advanced catalytic activity compared to single-component materials. Herein, we present preparation of the indium-doped tin oxide nanowires (In-SnO2 NWs) as an efficient electrocatalyst to promote CO2 reduction into formate. The unique 1D structure of SnO2 NWs with simultaneously doped-In (5.4at% In) can enhance the selectivity toward formate by up to-82 % compared to bare SnO2 NWs (-58.9 %) at-1.04 V (vs RHE). The modified SnO2 surface driven by In-doping induces electron delocalization in between, and the surface defects provide more active sites. Thus, the intermediate could be stably adsorbed to produce more formate ions.

Single-atom catalysts (SACs) are being widely developedfor theCO(2) reduction reaction (CO2RR) because of theirremarkable activity and selectivity. However, insufficient CO2RR performance and the poor long-term stability of the SACsremain obstacles to process scale-up. Herein, we explore Ni SACs (Ni-N/NCNT)under practical conditions using a zero-gap CO2 electrolyzerfor CO production. We demonstrate that the CO2RR performanceof the Ni-N/NCNT results from the suitable Ni-N-C, whichenhanced electron transfer and increased CO2 adsorption.Furthermore, we propose a strategy for improving the CO2RR performance and long-term stability by focusing on the membraneelectrode assembly (MEA) structure. A maximum Faradaic efficiencyof 96.73% (at 2.1 V) and partial current density of 219.49 mA cm(-2) (at 2.4 V) for CO production were obtained on theMEA with the Ni-N/NCNT catalyst and the Sustainion (Sust.) membrane.In addition, MEA with Sust. exhibited long-term stability at -100mA cm(-2) for over 60 h.

In this study, Ag/C composite catalysts with different weight ratios (20, 50, and 75 wt% Ag) were synthesized by spray pyrolysis to improve the performance of electrochemical CO2 reduction for CO production. Among the electrocatalysts tested, the Ag75/C composite catalyst (75 wt% of Ag nanoparticles dispersed in carbon black support) showed the highest electrochemical CO2 reduction performance, along with high stability that surpassed that of pure Ag particles. Above all, this is because Ag nanoparticles were dispersed on the surface of (and inside) the carbon black support. This enlarged the Ag surface area, thereby increasing the number of electrochemical CO2 reduction sites. Additionally, the carbon black support has a hierarchically porous structure that improved the transport of the catholyte, reactant, and products, enabling enhanced electrochemical CO2 reduction to CO. Furthermore, the use of carbon black support in the Ag/C composite catalysts allows the binder to bind more carbon microspheres than Ag nanoparticles, reducing the Ag surface area covered by the binder in comparison with that for pure Ag particles. Thus, the charge transfer resistance of a Ag/C composite catalyst was much lower than that of pure Ag particles due to the improved interconnection, contact, and number of electrochemical reaction sites provided by the combination of carbon black support and Ag nanoparticles. All of these interpretations imply that carbon black is an appropriate support able to play a key role in improving CO productivity via electrochemical CO2 reduction.

The electrochemical CO2 reduction reaction (CO2RR) to form C2+ products was investigated to obtain high selectivity in liquid CO2-fed systems having the limitation of low current density. Over the past decade, flow cells with gas diffusion electrodes (GDEs) have emerged to achieve high current densities close to the industrial-relevance scale by overcoming gas diffusion limitations. However, key parameters of GDE design, including binders, were not sufficiently identified to enhance selectivity and current density for C2+ products. Nafion, FAA-3, and polypyrrole were used to explore the effects of binder type and content on GDE properties such as porosity (gas permeability), ion conductivity, and electron conductivity for the modulation of the CO2RR on the Cu2O catalyst. The Cu2O GDEs with high binder content showed poor selectivity for C2+ products because of their low exposure to the catalyst surface and decreased gas permeability. The anion exchange ionomer, FAA-3, showed high selectivity for C2+ products and electrode stability resulting from the C???C coupling increase and suppression of the hydrogen evolution reaction, which was induced by OH??? conductivity. In contrast, the cation exchange ionomer, Nafion, exhibited low electrode stability due to the loss of gas products through the catholyte and due to its excessive wettability. Superscript/Subscript Available

The electrochemical reduction reaction of CO2 (CO2RR) is desirable for decreasing CO2 concentration in the atmosphere and producing value-added chemicals. The development of advanced catalysts is a key challenge for the practical application of CO2RR. Recently, the bimetallic catalysts with two or more reac-tion sites acting synergistically are one of the most interesting catalysts. Herein, CuAg bimetallic catalysts with various Cu/Ag ratios are synthesized by the ultrasonic spray pyrolysis (USP) method for the selective production of ethylene (C2H4) via CO2RR. The electrocatalytic performances of the CuAg catalysts with different compositions are evaluated in a full flow single cell and the Cu90Ag10 exhibits 1.5 times the higher C2H4 Faradaic efficiency and the C2H4 current density at a cell voltage of 2.2 V than the bare Cu. Ag in the bimetallic catalysts provides additional CO via desorption-re-adsorption and diffusion pro-cess for CAC coupling on the Cu surface to synthesize C2H4. In addition, the improved performance of the Cu90Ag10 is attributed to not only the synergistic effect between Cu and Ag but also the appropriate Cu/ Ag ratio. (c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

The CO2 atmospheric concentration level hit the record at more than 400 ppm and is predicted to keep increasing as the dependence on fossil fuels is inevitable. The CO2 electrocatalytic conversion becomes an alternative due to its environmental and energy-friendly properties and benign operation condition. Lately, bimetallic materials have drawn significant interest as electrocatalysts due to their distinct properties, which the parents' metal cannot mimic. Herein, the indium-bismuth nanosphere (In16Bi84 NS) was fabricated via the facile liquid-polyol technique. The In16Bi84 NS exhibits exceptional performance for CO2 reduction to formate, with the faradaic efficiency (FE) approaching ∼100% and a corresponding partial current density of 14.1 mA cm-2 at -0.94 V [vs the reversible hydrogen electrode (RHE)]. Furthermore, the FE could be maintained above 90% in a wide potential window (-0.84 to -1.54 V vs the RHE). This superior performance is attributed to the tuned electronic properties induced by the synergistic interaction between In and Bi, enabling the intermediates to be stably adsorbed on the catalyst surface to generate more formate ions.

Metallo-β-lactamase (MBL) superfamily proteins have a common αβ/βα sandwich fold and perform a variety of functions through metal-mediated catalysis. However, because of the enormous scale of this superfamily, only a small percentage of the proteins belonging to the superfamily have been annotated structurally or functionally to date. Therefore, much remains unknown about the MBL superfamily proteins. Here, TW9814, a hypothetical MBL superfamily protein, was structurally and functionally investigated. Guided by the crystal structure of dimeric TW9814, it was demonstrated that TW9814 functions as a phosphodiesterase (PDE) in the presence of divalent metal ions such as manganese(II) or nickel(II). A docking model between TW9814 and the substrate bis(p-nitrophenyl)phosphate (bpNPP) showed the importance of the dimerization of TW9814 for its bpNPP-hydrolyzing activity and for the interaction between the enzyme and the substrate. TW9814 showed outstanding catalytic efficiency (kcat/Km) under alkaline conditions compared with other PDEs. The activity of TW9814 appears to be regulated through a disulfide bond, which is a feature that is not present in other MBL superfamily members. This study provides a platform for the functional characterization of other hypothetical proteins of the MBL or other superfamilies.

Electrocatalytic reduction of CO2 to formate has become one way to increase the value of CO2 and to overcome the climate change issue. Novel catalysts for the critical role of enhancing reaction selectivity have been continuously explored to provide the best performance. Lately, composite materials have drawn much attention because the synergistic effect between the components provides enhanced physical and chemical properties. Here, we present a highly efficient CO2 reduction reaction to formate on a tin(IV) oxide/zinc oxide (SnO2/ZnO) composite electrocatalyst with a grainy hollow nanofiber (HNF) structure. The faradaic efficiency (FE) of formate on the SnO2/ZnO composite HNF reaches as high as 97.9% at -1.34 V vs reversible hydrogen electrode (RHE), outperforming many tin-based catalysts. At -1.54 V (vs RHE), the SnO2/ZnO HNF exhibits 2 times and 4 times higher current density for formate generation than those of SnO2 HNF and nanoparticles (NPs), respectively. This superior catalytic performance is attributed to its one-dimensional continuous structure as well as to the synergistic effects between SnO2 and ZnO, which facilitate faster electron transfer and improve the conductivity of SnO2/ZnO composite HNF.