Review—Non-Noble Metal-Based Single-Atom Catalysts for Efficient Electrochemical CO₂ Reduction Reaction

Abstract

Single-atom catalysts (SACs), as the name suggests, indicate that only one element participates in the catalytic reaction. The characteristic feature of SACs is that it has immobilized active sites with specific properties, such as unexpected catalytic activity, high product selectivity, and reduced energy barrier. SACs for electrochemical CO2 reduction reactions (CO2RR) should have isolated metal atoms acting as active sites to maximize the efficiency of metal use. Conventional metal catalysts with nano-sized metal particles, however, contain a variety of inactive sites showing inferior efficiency of metal use. Therefore, systematic synthesis and analysis of high-efficiency SACs have been an interesting challenge in the CO2RR. To address these issues, many researchers have attempted to synthesize SACs through various methods and employed numerous characterization techniques to identify single atoms and their electrochemical properties. In this review, we discuss recent trends in the synthesis strategies and analyzing techniques of SACs and explain the influence of SACs on electrochemical CO2RR mechanisms of various C1 and C2 products.

MOF-Templated Sulfurization of Atomically Dispersed Manganese Catalysts Facilitating Electroreduction of CO2 to CO

“…Such a catalytic performance is general in literature. One of possible explanations for it is that isolated metal atoms in SACs prevent the absorbed *CO from forming a coupling of OC–CO dimer, a precursor for multicarbon products, while the debate regarding the mechanism is still open . A close inspection on the performance of the Mn SA /NC (Figure b) was first carried out.…”

“…One of possible explanations for it is that isolated metal atoms in SACs prevent the absorbed *CO from forming a coupling of OC−CO dimer, a precursor for multicarbon products, while the debate regarding the mechanism is still open. 64 A close inspection on the performance of the Mn SA / NC (Figure 3b) was first carried out. At the initial applied potential, −0.35 V, the Mn SA /NC demonstrated its preference for CO 2 with a slightly higher F.E.…”

2.6% cm–2 Single-Pass CO2-to-CO Conversion Using Ni Single Atoms Supported on Ultra-Thin Carbon Nanosheets in a Flow Electrolyzer

“…[8][9][10] Specifically, nitrogen-doped carbon with the inclusions of metal single atoms (M-N-C) has been investigated for several key electrochemical reactions including the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR) and also the CO2RR. [11][12][13] The search for highly active CO2RR catalysts is typically carried out using traditional "H-cell" reactors. The performance is however severely limited by the relatively low CO2 dissolvability in the liquid electrolyte.…”

“…Among the various strategies, the electrochemical CO 2 reduction reaction (CO 2 RR) under ambient conditions, which can be coupled with renewable electricity sources, represents a promising approach to reuse the CO 2 emissions, while generating value-added fuels and chemicals. , In this context, a vast amount of efforts are currently being devoted to the development of novel electrocatalysts with optimum selectivity and activity toward the production of various C 1 –C 3 molecules. , The discovery of single-atom catalysts has extended new directions for the rational design of heterogeneous catalysts with a well-defined structure and maximum exposure of the active sites . Single-atom catalysts have been demonstrated with outstanding electrochemical CO 2 RR selectivity and high current densities thanks to the peculiar coordination environment of the single-metal atom and the local electronic structures that differ from those of the nanoparticle counterparts. − Specifically, nitrogen-doped carbon with the inclusions of metal single atoms (M–N–C) has been investigated for several key electrochemical reactions including the hydrogen evolution reaction (HER), the oxygen reduction reaction, and also the CO 2 RR. − …”

In Situ Electrochemical Route to Bromide Anion-Adsorbed Coral-like Porous Silver Microspheres Achieving Highly Selective Electroreduction of CO2 to CO over a Wide Potential Range

“…Recently, a variety of efficient catalysts have been developed for CO 2 electroreduction to CO, including noble and non-noble metal catalysts, − transition-metal chalcogenide catalysts, metal complex catalysts, , single-atom catalysts, − and others . Noble metal catalysts still have some advantages compared to other types of catalysts, such as high selectivity at low voltages, simple and gentle synthesis methods, excellent conductivity, and suitability for stable production.…”