Search

Halide anion adsorption on transition metals can improve the performance of electrochemical CO 2 reduction reaction (CO 2 RR), while the specific reaction mechanisms governing selective CO 2 RR pathways remain unclear. In this study, we reveal for the first time the distinct pathway switching between gaseous (CO) and liquid products (formate and ethanol) on the well-defined Ag-Cu nanostructures with controlled chlorination. We show that CO 2 conversion to CO on Ag/AgCl can be tuned by adjusting the thickness of AgCl layer, achieving a high selectivity over a broad potential range in a 0.5 M KHCO 3 using flow cell. In contrast, the optimized Cl-Ag/Cu system enables the conversion of CO 2 into liquid products including formate and ethanol with a total Faradaic efficiency (FE) nearing 100 %, delivering high current densities of 136.3 and 20.8 mA cm -2 at -1.3 V, respectively. In situ infrared experiments and theoretical calculations indicate that the lateral adsorbate of *OCHO intermediate facilitates the thermodynamics of both the CO pathway on Cl-Ag(111) and the formate pathway on Cl-Ag/Cu(111) by reducing Gibbs free energy barriers of each potential-limit step. This work uncovers the role of chlorination in the tuning of C-bound or O-bound intermediates during CO 2 RR on Ag-Cu catalysts, determining the reaction pathway under lateral adsorbate effects., (© 2024 Wiley-VCH GmbH.)

Renewable electricity shows immense potential as a driving force for the carbon dioxide reduction reaction (CO 2 RR) in production of formate (HCOO - ) at industrial current density, providing a promising path for value-added chemicals and chemical manufacturing. However, achieving high selectivity and stable production of HCOO - at industrial current density remains a challenge. Here, we present a robust Bi 0.6 Cu 0.4 NSs catalyst capable of regenerating necessary catalytic core (Bi-O) through cyclic voltammetry (CV) treatment. Notably, at 260 mA cm -2 , faradaic efficiency of HCOO - reaches an exceptional selectivity to 99.23 %, maintaining above 90 % even after 400 h, which is longest reaction time reported at the industrial current density. Furthermore, in stability test, the catalyst was constructed by CV reconstruction to achieve stable and efficient production of HCOO - . In 20 h reaction test, the catalyst has a rate of HCOO - production of 13.24 mmol m -2  s -1 , a HCOO - concentration of 1.91 mol L -1 , and an energy consumption of 129.80 kWh kmol -1 . In situ Raman spectroscopy reveals the formation of Bi-O structure during the gradual transformation of catalyst from Bi 0.6 Cu 0.4 NBs to Bi 0.6 Cu 0.4 NSs. Theoretical studies highlight the pivotal role of Bi-O structure in modifying the adsorption behavior of reaction intermediates, which further reduces energy barrier for *OCHO conversion in CO 2 RR., (© 2024 Wiley-VCH GmbH.)

Fine-tuning the interfacial sites within heterogeneous catalysts is pivotal for unravelling the intricate structure-property relationship and optimizing their catalytic performance. Herein, a simple and versatile mixed-dimensional assembly approach is proposed to create nanocrystal-on-nanowire superstructures with precisely adjustable numbers of biphasic interfaces. This method leverages an efficient self-assembly process in which colloidal nanocrystals spontaneously organize onto Ag nanowires, driven by the solvophobic effect. Importantly, varying the ratio of the two components during assembly allows for accurate control over both the quantity and contact perimeter of biphasic interfaces. As a proof-of-concept demonstration, a series of Au-on-Ag superstructures with varying numbers of Au/Ag interfaces are constructed and employed as electrocatalysts for electrochemical CO 2 -to-CO conversion. Experimental results reveal a logarithmic linear relationship between catalytic activity and the number of Au/Ag interfaces per unit mass of Au-on-Ag superstructures. This work presents a straightforward approach for precise interface engineering, paving the way for systematic exploration of interface-dependent catalytic behaviors in heterogeneous catalysts., (© 2024 Wiley-VCH GmbH.)

Electrocatalytic reduction of CO 2 into C 2 products of high economic value provides a promising strategy to realize resourceful CO 2 utilization. Rational design and construct dual sites to realize the CO protonation and C-C coupling to unravel their structure-performance correlation is of great significance in catalysing electrochemical CO 2 reduction reactions. Herein, Cu-Cu dual sites with different site distance coordinated by halogen at the first-shell are constructed and shows a higher intramolecular electron redispersion and coordination symmetry configurations. The long-range Cu-Cu (Cu-I-Cu) dual sites show an enhanced Faraday efficiency of C 2 products, up to 74.1 %, and excellent stability. In addition, the linear relationships that the long-range Cu-Cu dual sites are accelerated to C 2 H 4 generation and short-range Cu-Cu (Cu-Cl-Cu) dual sites are beneficial for C 2 H 5 OH formation are disclosed. In situ electrochemical attenuated total reflection surface enhanced infrared absorption spectroscopy, in situ Raman and theoretical calculations manifest that long-range Cu-Cu dual sites can weaken reaction energy barriers of CO hydrogenation and C-C coupling, as well as accelerating deoxygenation of *CH 2 CHO. This study uncovers the exploitation of site-distance-dependent electrochemical properties to steer the CO 2 reduction pathway, as well as a potential generic tactic to target C 2 synthesis by constructing the desired Cu-Cu dual sites., (© 2024 Wiley-VCH GmbH.)

Dual-single-atom catalysts (DSACs) are the next paradigm shift in single-atom catalysts because of the enhanced performance brought about by the synergistic effects between adjacent bimetallic pairs. However, there are few methods for synthesizing DSACs with precise bimetallic structures. Herein, a pre-coordination strategy is proposed to precisely synthesize a library of DSACs. This strategy ensures the selective and effective coordination of two metals via phthalocyanines with specific coordination sites, such as -F- and -OH-. Subsequently, in situ confinement inhibits the migration of metal pairs during high-temperature pyrolysis, and obtains the DSACs with precisely constructed metal pairs. Despite changing synthetic parameters, including transition metal centers, metal pairs, and spatial geometry, the products exhibit similar atomic metal pairs dispersion properties, demonstrating the universality of the strategy. The pre-coordination strategy synthesized DSACs shows significant CO 2 reduction reaction performance in both flow-cell and practical rechargeable Zn-CO 2 batteries. This work not only provides new insights into the precise synthesis of DSACs, but also offers guidelines for the accelerated discovery of efficient catalysts., (© 2024 Wiley-VCH GmbH.)

Although gapped grain boundaries have often been observed in bulk and nanosized materials, and their crucial roles in some physical and chemical processes have been confirmed, their acquisition at ultrasmall nanoscale presents a significant challenge. To date, they had not been reported in metal nanoparticles smaller than 2 nm owing to the difficulty in characterization and the high instability of grain boundary (GB) atoms. Herein, we have successfully developed a synthesis method for producing a novel chiral nanocluster Au 78 (TBBT) 40 (TBBT=4-tert-butylphenylthiolate) with a 26-atom gapped and rotated GB. This nanocluster was precisely characterized using single-crystal X-ray crystallography and mass spectrometry. Additionally, an offset atomic defect linked to the peripheral Au(TBBT) 2 staple was found in the structure. Comparing it to similarly face-centered cubic-structured Au 36 (TBBT) 24 , Au 44 (TBBT) 28 , Au 52 (TBBT) 32 , Au 92 (TBBT) 44 , and ~5 nm nanocrystals, the bridging Au 78 (TBBT) 40 nanocluster exhibited higher catalytic activity in the electroreduction of CO 2 to CO. This enhanced activity was explained through density functional theory calculations and X-ray photoelectron spectroscopy analysis, which highlight the impact of GBs and point defects on the surface properties of metal nanoclusters in balancing intermediate adsorption and product desorption., (© 2024 Wiley-VCH GmbH.)

Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) to valuable liquid fuels, such as formic acid/formate (HCOOH/HCOO - ) is a promising strategy for carbon neutrality. Enhancing CO 2 RR activity while retaining high selectivity is critical for commercialization. To address this, we developed metal-doped bismuth (Bi) nanosheets via a facile hydrolysis method. These doped nanosheets efficiently generated high-purity HCOOH using a porous solid electrolyte (PSE) layer. Among the evaluated metal-doped Bi catalysts, Co-doped Bi demonstrated improved CO 2 RR performance compared to pristine Bi, achieving ~90 % HCOO - selectivity and boosted activity with a low overpotential of ~1.0 V at a current density of 200 mA cm -2 . In a solid electrolyte reactor, Co-doped Bi maintained HCOOH Faradaic efficiency of ~72 % after a 100-hour operation under a current density of 100 mA cm -2 , generating 0.1 M HCOOH at 3.2 V. Density functional theory (DFT) results revealed that Co-doped Bi required a lower applied potential for HCOOH generation from CO 2 , due to stronger binding energy to the key intermediates OCHO* compared to pure Bi. This study shows that metal doping in Bi nanosheets modifies the chemical composition, element distribution, and morphology, improving CO 2 RR catalytic activity performance by tuning surface adsorption affinity and reactivity., (© 2024 Wiley-VCH GmbH.)

The electrochemical CO 2 reduction reaction (eCO 2 RR) to multicarbon products has been widely recognized for Cu-based catalysts. However, the structural changes in Cu-based catalysts during the eCO 2 RR pose challenges to achieving an in-depth understanding of the structure-activity relationship, thereby limiting catalyst development. Herein, we employ constant-potential density functional theory calculations to investigate the sintering process of Cu single atoms of Cu-N-C single-atom catalysts into clusters under eCO 2 RR conditions. Systematic constant-potential ab initio molecular dynamics simulations revealed that the leaching of Cu-(CO) x moieties and subsequent agglomeration into clusters can be facilitated by synergistic adsorption of H and eCO 2 RR intermediates (e.g., CO). Increasing the Cu 2+ concentration or the applied potential can efficiently suppress Cu sintering. Both microkinetic simulations and experimental results further confirm that sintered Cu clusters play a crucial role in generating C 2 products. These findings provide significant insights into the dynamic evolution of Cu-based catalysts and the origin of their activity toward C 2 products during the eCO 2 RR., (© 2024 Wiley-VCH GmbH.)

Cu-based catalysts have been identified as the most promising candidates for generation of C2+ products in electrochemical CO 2 reduction reaction. Defect engineering in catalysts is a widely employed strategy for promoting C-C coupling on Cu. However, comprehensive understanding of defect structure-to-activity relationship has not been obtained. In this study, controllable defects generation is achieved, which leads to a series of Cu-based catalysts with various phase mixing degrees. It is observed that the Faradaic efficiency toward C2+ products increases with the phase mixing degree, reaching 81 % at maximum. In situ infrared absorption spectroscopy reveals that the catalysts with higher phase mixing degree tend to form *CO more easily and possess higher retention of *CO under high overpotential window, thereby promoting C-C coupling. This work sheds new light on the relationship between defects and C-C coupling, and the rational developed of more advanced Cu-base catalysts., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Plasmon-mediated electrocatalysis that rests on the ability of coupling localized surface plasmon resonance (LSPR) and electrochemical activation, emerges as an intriguing and booming area. However, its development seriously suffers from the entanglement between the photoelectronic and photothermal effects induced by the decay of plasmons, especially under the influence of applied potential. Herein, using LSPR-mediated CO 2 reduction on Ag electrocatalyst as a model system, we quantitatively uncover the dominant photoelectronic effect on CO 2 reduction reaction over a wide potential window, in contrast to the leading photothermal effect on H 2 evolution reaction at relatively negative potentials. The excitation of LSPR selectively enhances the CO faradaic efficiency (17-fold at -0.6 V RHE ) and partial current density (100-fold at -0.6 V RHE ), suppressing the undesired H 2 faradaic efficiency. Furthermore, in situ attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals a plasmon-promoted formation of the bridge-bonded CO on Ag surface via a carbonyl-containing C1 intermediate. The present work demonstrates a deep mechanistic understanding of selective regulation of interfacial reactions by coupling plasmons and electrochemistry., (© 2024 Wiley-VCH GmbH.)

Catalysts involving post-transition metals have shown almost invincible performance on generating formate in electrochemical CO 2 reduction reaction (CO 2 RR). Conversely, Cu without post-transition metals has struggled to achieve comparable activity. In this study, a sulfur (S)-doped-copper (Cu)-based catalyst is developed, exhibiting excellent performance in formate generation with a maximum Faradaic efficiency of 92 % and a partial current density of 321 mA cm -2 . Ex situ structural elucidations reveal the presence of abundant grain boundaries and high retention of S-S bonds from the covellite phase during CO 2 RR. Furthermore, thermodynamic calculations demonstrate that S-S bonds can moderate the binding energies with various intermediates, further improving the activity of the formate pathway. This work is significant in modifying a low-cost catalyst (Cu) with a non-metallic element (S) to achieve comparable performance to mainstream catalysts for formate generation in industrial grade., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Addressing the limitations arising from the consistent catalytic behavior observed for various intermediates during the electrochemical carbon dioxide reduction reaction (CO 2 RR) poses a significant challenge in the optimization of catalytic activity. In this study, we aimed to address this challenge by constructing an asymmetric coordination Fe single atom catalyst (SCA) with a dynamically evolved structure. Our catalyst, consisting of a Fe atom coordinated with one S atom and three N atoms (Fe-S 1 N 3 ), exhibited exceptional selectivity (CO Faradaic efficiency of 99.02 %) and demonstrated a high intrinsic activity (TOF of 7804.34 h -1 ), and remarkable stability. Using operando XAFS spectra and Density Functional Theory (DFT) calculations, we elucidated the self-relaxation of geometric distortion and dynamic evolution of bond lengths within the catalyst. These structure changes enabled independent regulation of the *COOH and *CO intermediate adsorption energies, effectively breaking the linear scale relationship and enhancing the intrinsic activity of CO 2 RR. This study provides valuable insights into the dynamic evolution of SACs and paves the way for targeted catalyst designs aimed to disrupt the linear scaling relationships., (© 2023 Wiley-VCH GmbH.)

Modulation of the microenvironment on the electrode surface is one of the effective means to improve the efficiency of electrocatalytic carbon dioxide reduction (eCO 2 RR). To achieve high conversion rates, the phase boundary at the electrode surface should be finely controlled to overcome the limitation of CO 2 solubility in the aqueous electrolyte. Herein, we developed a simple and efficient method to structure electrocatalyst with a superhydrophobic surface microenvironment by one-step co-electrodeposition of Cu and polytetrafluoroethylene (PTFE) on carbon paper. The super-hydrophobic Cu-based electrode displayed a high ethylene (C 2 H 4 ) selectivity with a Faraday efficiency (FE) of 67.3 % at -1.25 V vs. reversible hydrogen electrode (RHE) in an H-type cell, which is 2.5 times higher than a regular Cu electrode without PTFE. By using PTFE as a surface modifier, the activity of eCO 2 RR is enhanced and water (proton) adsorption is inhibited. This strategy has the potential to be applied to other gas-conversion electrocatalysts., (© 2023 Wiley-VCH GmbH.)

Electrochemical CO 2 reduction to value-added chemicals or fuels offers a promising approach to reduce carbon emissions and alleviate energy shortage. Cu-based electrocatalysts have been widely reported as capable of reducing CO 2 to produce a variety of multicarbon products (e.g., ethylene and ethanol). In this work, we develop sulfur-doped Cu 2 O electrocatalysts, which instead can electrochemically reduce CO 2 to almost exclusively formate. We show that a dynamic equilibrium of S exists at the Cu 2 O-electrolyte interface, and S-doped Cu 2 O undergoes in situ surface reconstruction to generate active S-adsorbed metallic Cu sites during the CO 2 reduction reaction (CO 2 RR). Density functional theory (DFT) calculations together with in situ infrared absorption spectroscopy measurements show that the S-adsorbed metallic Cu surface can not only promote the formation of the *OCHO intermediate but also greatly suppress *H and *COOH adsorption, thus facilitating CO 2 -to-formate conversion during the electrochemical CO 2 RR., (© 2023 Wiley-VCH GmbH.)

Rational regulation of electronic structures and functionalities of framework materials still remains challenging. Herein, reaction of 4,4',4''-nitrilo-tribenzhydrazide with tris(μ 2 -4-carboxaldehyde-pyrazolato-N,N')-tricopper (Cu 3 Py 3 ) generates the crystalline copper organic framework USTB-11(Cu). Post-modification with divalent nickel ions affords the heterometallic framework USTB-11(Cu,Ni). Powder X-ray diffraction and theoretical simulations reveal their two-dimensional hexagonal structure geometry. A series of advanced spectroscopic techniques disclose the mixed Cu I /Cu II state nature of Cu 3 Py 3 in USTB-11(Cu,Ni) with a uniform bistable Cu 3 4+ (Cu I 2 Cu II ) : Cu 3 5+ (Cu I Cu II 2 ) (ca. 1 : 3) oxidation state, resulting in a significantly improved formation efficiency of the charge-separation state. This endows the Ni sites with enhanced activity and USTB-11(Cu,Ni) with outstanding photocatalytic CO 2 to CO performance with a conversion rate of 22 130 μmol g -1  h -1 and selectivity of 98 %., (© 2023 Wiley-VCH GmbH.)

Fine-tuning electronic structures of single-atom catalysts (SACs) plays a crucial role in harnessing their catalytic activities, yet challenges remain at a molecular scale in a controlled fashion. By tailoring the structure of graphdiyne (GDY) with electron-withdrawing/-donating groups, we show herein the electronic perturbation of Cu single-atom CO 2 reduction catalysts in a molecular way. The elaborately introduced functional groups (-F, -H and -OMe) can regulate the valance state of Cu δ+ , which is found to be directly scaled with the selectivity of the electrochemical CO 2 -to-CH 4 conversion. An optimum CH 4 Faradaic efficiency of 72.3 % was achieved over the Cu SAC on the F-substituted GDY. In situ spectroscopic studies and theoretical calculations revealed that the positive Cu δ+ centers adjusted by the electron-withdrawing group decrease the pK a of adsorbed H 2 O, promoting the hydrogenation of intermediates toward the CH 4 production. Our strategy paves the way for precise electronic perturbation of SACs toward efficient electrocatalysis., (© 2022 Wiley-VCH GmbH.)

Copper (Cu) remains the most important metal catalyst for the carbon dioxide reduction reaction (CO 2 RR) into C 2 products. Due to limited evidence from in situ experiments, mechanistic studies are often performed in the framework of density functional theory (DFT), using functionals at the generalized gradient approximation (GGA) level, which have fundamental difficulties to correctly describe CO adsorption and surface stability. We employ the adiabatic connection fluctuation dissipation theorem within the random phase approximation (RPA), in combination with the linearized Poisson-Boltzmann equation to describe solvation effects, to investigate the mechanism of CO 2 RR on the Cu(100) facet. Qualitatively different from the DFT-GGA results, RPA results propose the formation of *OCCHO as the potential determining step towards C 2 products. The results suggest that it is important to use more accurate methods like RPA when modeling reactions involving multiple CO-related species like CO 2 RR., (© 2022 Wiley-VCH GmbH.)

Electrochemical CO 2 -to-CO conversion provides a possible way to address problems associated with the greenhouse effect; however, developing low-cost electrocatalysts to mediate high-efficiency CO 2 reduction remains a challenge on account of the limited understanding of the nature of the real active sites. Herein, we reveal the Zn δ+ metalloid sites as the real active sites of stable nonstoichiometric ZnO x structure derived from Zn 2 P 2 O 7 through operando X-ray absorption fine structure analysis in conjunction with evolutionary-algorithm-based global optimization. Furthermore, theoretical and experimental results demonstrated that Zn δ+ metalloid active sites could facilitate the activation of CO 2 and the hydrogenation of *CO 2 , thus accelerating the CO 2 -to-CO conversion. Our work establishes a critical fundamental understanding of the origin of the real active center in the zinc-based electrocatalysts for CO 2 reduction reaction., (© 2022 Wiley-VCH GmbH.)

Cu 2 O microparticles with controllable crystal planes and relatively high stability have been recognized as a good platform to understand the mechanism of the electrocatalytic CO 2 reduction reaction (CO 2 RR). Herein, we demonstrate that the in situ generated Cu 2 O/Cu interface plays a key role in determining the selectivity of methane formation, rather than the initial crystal plane of the reconstructed Cu 2 O microparticles. Experimental results indicate that the methane evolution is dominated on all three different crystal planes with similar Tafel slopes and long-term stabilities. Density functional theory (DFT) calculations further reveal that *CO is protonated via a similar bridge configuration at the Cu 2 O/Cu interface, regardless of the initial crystal planes of Cu 2 O. The Gibbs free energy changes (ΔG) of *CHO on different reconstructed Cu 2 O planes are close and more negative than that of *OCCOH, indicating the methane formation is more favorable than ethylene on all Cu 2 O crystal planes., (© 2021 Wiley-VCH GmbH.)

Copper-based materials are efficient electrocatalysts for the conversion of CO 2 to C 2+ products, and most these materials are reconstructed in situ to regenerate active species. It is a challenge to precisely design precatalysts to obtain active sites for the CO 2 reduction reaction (CO 2 RR). Herein, we develop a strategy based on local sulfur doping of a Cu-based metal-organic framework precatalyst, in which the stable Cu-S motif is dispersed in the framework of HKUST-1 (S-HKUST-1). The precatalyst exhibits a high ethylene selectivity in an H-type cell with a maximum faradaic efficiency (FE) of 60.0 %, and delivers a current density of 400 mA cm -2 with an ethylene FE up to 57.2 % in a flow cell. Operando X-ray absorption results demonstrate that Cu δ+ species stabilized by the Cu-S motif exist in S-HKUST-1 during CO 2 RR. Density functional theory calculations indicate the partially oxidized Cu δ+ at the Cu/Cu x S y interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimized adsorption energy., (© 2021 Wiley-VCH GmbH.)

We report the fabrication of homoleptic alkynyl-protected Ag 15 (C≡C- t Bu) 12 + (abbreviated as Ag 15 ) nanocluster and its electrocatalytic properties toward CO 2 reduction reaction. Crystal structure analysis reveals that Ag 15 possesses a body-centered-cubic (BCC) structure with an Ag@Ag 8 @Ag 6 metal core configuration. Interestingly, we found that Ag 15 can adsorb CO 2 in the air and spontaneously self-assembled into one-dimensional linear material during the crystal growth process. Furthermore, Ag 15 can convert CO 2 into CO with a faradaic efficiency of ca. 95.0 % at -0.6 V and a maximal turnover frequency of 6.37 s -1 at -1.1 V along with excellent long-term stability. Finally, density functional theory (DFT) calculations disclosed that Ag 15 (C≡C- t Bu) 11 + with one alkynyl ligand stripping off from the intact cluster can expose the uncoordinated Ag atom as the catalytically active site for CO formation., (© 2021 Wiley-VCH GmbH.)

Dual-atom site catalysts (DACs) have emerged as a new frontier in heterogeneous catalysis because the synergistic effect between adjacent metal atoms can promote their catalytic activity while maintaining the advantages of single-atom site catalysts (SACs), like 100 % atomic utilization efficiency and excellent selectivity. Herein, a supported Pd 2 DAC was synthesized and used for electrochemical CO 2 reduction reaction (CO 2 RR) for the first time. The as-obtained Pd 2 DAC exhibited superior CO 2 RR catalytic performance with 98.2 % CO faradic efficiency at -0.85 V vs. RHE, far exceeding that of Pd 1 SAC, and coupled with long-term stability. The density functional theory (DFT) calculations revealed that the intrinsic reason for the superior activity of Pd 2 DAC toward CO 2 RR was the electron transfer between Pd atoms at the dimeric Pd sites. Thus, Pd 2 DAC possessed moderate adsorption strength of CO*, which was beneficial for CO production in CO 2 RR., (© 2021 Wiley-VCH GmbH.)

Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) is an attractive approach to deal with the emission of CO 2 and to produce valuable fuels and chemicals in a carbon-neutral way. Many efforts have been devoted to boost the activity and selectivity of high-value multicarbon products (C 2+ ) on Cu-based electrocatalysts. However, Cu-based CO 2 RR electrocatalysts suffer from poor catalytic stability mainly due to the structural degradation and loss of active species under CO 2 RR condition. To date, most reported Cu-based electrocatalysts present stabilities over dozens of hours, which limits the advance of Cu-based electrocatalysts for CO 2 RR. Herein, a porous chlorine-doped Cu electrocatalyst exhibits high C 2+ Faradaic efficiency (FE) of 53.8 % at -1.00 V versus reversible hydrogen electrode (V RHE ). Importantly, the catalyst exhibited an outstanding catalytic stability in long-term electrocatalysis over 240 h. Experimental results show that the chlorine-induced stable cationic Cu 0 /Cu + species and the well-preserved structure with abundant active sites are critical to the high FE of C 2+ in the long-term run of electrochemical CO 2 reduction., (© 2021 Wiley-VCH GmbH.)

The design of catalysts with high activity, selectivity, and stability is key to the electroreduction of CO 2 . Herein, we report the synthesis of 3D hierarchical metal/polymer-carbon paper (M/polymer-CP) electrodes by in situ electrosynthesis. The 3D polymer layer on CP (polymer-CP) was first prepared by in situ electropolymerization, then a 3D metal layer was decorated on the polymer-CP to produce the M/polymer-CP electrode. Electrodes with different metals (e.g. Cu, Pd, Zn, Sn) and various polymers could be prepared by this method. The electrodes could efficiently reduce CO 2 to desired products, such as C 2 H 4 , CO, and HCOOH, depending on the metal used. For example, C 2 H 4 could be formed with a Faradaic efficiency of 59.4 % and a current density of 30.2 mA cm -2 by using a very stable Cu/PANI-CP electrode in an H-type cell. Control experiments and theoretical calculations showed that the 3D hierarchical structure of the metals and in situ formation of the electrodes are critical for the excellent performance., (© 2021 Wiley-VCH GmbH.)

We report an Ag 1 single-atom catalyst (Ag 1 /MnO 2 ), which was synthesized from thermal transformation of Ag nanoparticles (NPs) and surface reconstruction of MnO 2 . The evolution process of Ag NPs to single atoms is firstly revealed by various techniques, including in situ ETEM, in situ XRD and DFT calculations. The temperature-induced surface reconstruction process from the MnO 2 (211) to (310) lattice plane is critical to firmly confine the existing surface of Ag single atoms; that is, the thermal treatment and surface reconstruction of MnO 2 is the driving force for the formation of single Ag atoms. The as-obtained Ag 1 /MnO 2 achieved 95.7 % Faradic efficiency at -0.85 V vs. RHE, and coupled with long-term stability for electrochemical CO 2 reduction reaction (CO 2 RR). DFT calculations indicated single Ag sites possessed high electronic density close to Fermi Level and could act exclusively as the active sites in the CO 2 RR. As a result, the Ag 1 /MnO 2 catalyst demonstrated remarkable performance for the CO 2 RR, far surpassing the conventional Ag nanosized catalyst (Ag NP /MnO 2 ) and other reported Ag-based catalysts., (© 2020 Wiley-VCH GmbH.)

Photo/electrocatalysis of water (H 2 O) splitting and CO 2 reduction reactions is a promising strategy to alleviate the energy crisis and excessive CO 2 emissions. For the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and CO 2 reduction reaction (CO 2 RR) involved, the development of effective photo/electrocatalysts is critical to reduce the activation energy and accelerate the sluggish dynamics. Polyoxometalate (POM)-based compounds with tunable compositions and diverse structures are emerging as unique photo/electrocatalysts for these reactions as they offer unparalleled advantages such as outstanding solution and redox stability, quasi-semiconductor behaviour, etc. This Minireview provides a basic introduction related to photo/electrocatalytic HER, OER and CO 2 RR, followed by the classification of pristine POM-based compounds toward different catalytic reactions. Recent breakthroughs in engineering POM-based compounds as efficient photo/electrocatalysts are highlighted. Finally, the advantages, challenges, strategies and outlooks of POM-based compounds on improving photo/electrocatalytic performance are discussed., (© 2020 Wiley-VCH GmbH.)

Metal oxides or sulfides are considered to be one of the most promising CO 2 reduction reaction (CO 2 RR) precatalysts, owing to their electrochemical conversion in situ into highly active electrocatalytic species. However, further improvement of the performance requires new tools to gain fine control over the composition of the active species and its structural features [e.g., grain boundaries (GBs) and undercoordinated sites (USs)], directly from a predesigned template material. Herein, we describe a novel electrochemically driven cation exchange (ED-CE) method that enables the conversion of a predesigned CoS 2 template into a CO 2 RR catalyst, Cu 2 S. By means of ED-CE, the final Cu 2 S catalyst inherits the original 3 D morphology of CoS 2 , and preserves its high density of GBs. Additionally, the catalyst's phase structure, composition, and density of USs were precisely tuned, thus enabling rational design of active CO 2 RR sites. The obtained Cu 2 S catalyst achieved a CO 2 -to-formate Faradaic efficiency of over 87 % and a record high activity (among reported Cu-based catalysts). Hence, this study opens the way for utilization of ED-CE reactions to design advanced electrocatalysts., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrochemical reduction of CO 2 into various chemicals and fuels provides an attractive pathway for environmental and energy sustainability. It is now shown that a FeP nanoarray on Ti mesh (FeP NA/TM) acts as an efficient 3D catalyst electrode for the CO 2 reduction reaction to convert CO 2 into alcohols with high selectivity. In 0.5 m KHCO 3 , such FeP NA/TM is capable of achieving a high Faradaic efficiency (FE CH 3 OH ) up to 80.2 %, with a total FE CH 3 OH + C 2 H 5 OH of 94.3 % at -0.20 V vs. reversible hydrogen electrode. Density functional theory calculations reveal that the FeP(211) surface significantly promotes the adsorption and reduction of CO 2 toward CH 3 OH owing to the synergistic effect of two adjacent Fe atoms, and the potential-determining step is the hydrogenation process of *CO., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrochemical conversion of CO 2 into fuels using electricity generated from renewable sources helps to create an artificial carbon cycle. However, the low efficiency and poor stability hinder the practical use of most conventional electrocatalysts. In this work, a 2D hierarchical Pd/SnO 2 structure, ultrathin Pd nanosheets partially capped by SnO 2 nanoparticles, is designed to enable multi-electron transfer for selective electroreduction of CO 2 into CH 3 OH. Such a structure design not only enhances the adsorption of CO 2 on SnO 2 , but also weakens the binding strength of CO on Pd due to the as-built Pd-O-Sn interfaces, which is demonstrated to be critical to improve the electrocatalytic selectivity and stability of Pd catalysts. This work provides a new strategy to improve electrochemical performance of metal-based catalysts by creating metal oxide interfaces for selective electroreduction of CO 2 ., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)