Heterogeneous Single‐Atom Catalysts for Electrochemical CO₂ Reduction Reaction

Abstract

The electrochemical CO2 reduction reaction (CO2RR) is of great importance to tackle the rising CO2 concentration in the atmosphere. The CO2RR can be driven by renewable energy sources, producing precious chemicals and fuels, with the implementation of this process largely relying on the development of low‐cost and efficient electrocatalysts. Recently, a range of heterogeneous and potentially low‐cost single‐atom catalysts (SACs) containing non‐precious metals coordinated to earth‐abundant elements have emerged as promising candidates for the CO2RR. Unfortunately, the real catalytically active centers and the key factors that govern the catalytic performance of these SACs remain ambiguous. Here, this ambiguity is addressed by developing a fundamental understanding of the CO2RR‐to‐CO process on SACs, as CO accounts for the major product from CO2RR on SACs. The reaction mechanism, the rate‐determining steps, and the key factors that control the activity and selectivity are analyzed from both experimental and theoretical studies. Then, the synthesis, characterization, and the CO2RR performance of SACs are discussed. Finally, the challenges and future pathways are highlighted in the hope of guiding the design of the SACs to promote and understand the CO2RR on SACs.

Designing the future atomic electrocatalyst for efficient energy systems

“…The electrochemical CO 2 is capable of both mitigating the CO 2 emission and supplying sustainable energy to society and also tuning CO 2 into useful chemicals. 29 However, the CO 2 RR process is still hampered by the lack of efficient electrocatalysts, low energy efficiency, slow reaction rate, and poor selectivity. SAC is a promising candidate for efficient CO 2 RR with its multiple advantages over the conventional heterogeneous and homogeneous catalyst, for example, unique electronic structures, low-coordination number, and maximum atom utilization.…”

“…For the nanostructured catalysts, the adsorption of CO 2 and H 2 O may occur simultaneously on the continuous surface ( Figure 8A). 29 Moreover, nanostructured metal-based catalysts generally possess various facets and binding sites, which often exhibit different binding strength toward CO 2 , H 2 O, and intermediates. To date, most of the reported heterogeneous SACs for CO 2 RR is classified into the following three types: pyrolyzed M-N-C catalysts, graphene-supported SACs, and MOFs-derived SACs ( Table 5).…”

“…First is the products of CO 2 RR beyond CO. Other products like formic acid, methane, methanol, and even ethanol are more desirable with their higher energy density and corresponding SACs have been synthesized. 29 Cu-based SACs are also receiving interest for CO 2 RR since they are prone to produce deep reduction products like hydrocarbons and alcohols. 144,155 Finally, future developments on the fabrication of SACs for CO 2 RR are also needed to further improve the performance.…”

“…5 The SAC usually possesses distinct and outstanding performance in many electrochemical reactions, for example, oxygen reduction reaction (ORR), [6][7][8][9][10][11] oxygen evolution reaction (OER), [12][13][14][15][16] hydrogen evolution reaction (HER), [17][18][19][20] nitrogen reduction reaction (NRR), [21][22][23][24][25][26][27][28] and carbon dioxide reduction. 29 The excellent activity of SACs generally stems from the unique single-atom motifs as active sites on the surface. The single atom sites have unique geometry and electronic properties since the metal-metal bonds are absent, and the valence states of the isolated active sites can be tuned by electron-transfer with the anchored support.…”

Cobalt-Based Metal-Organic Frameworks and Their Derivatives for Hydrogen Evolution Reaction

“…The green and sustainable supply of hydrogen is essential for the hydrogen economy. At present, hydrogen is mainly obtained through a steam reforming of fossil fuels, which not only consumes a large amount of non-renewable energy, but also increases CO 2 emissions (Qin et al, 2016 ; Li M. et al, 2017a , b ). Therefore, to produce hydrogen in a clean and renewable way is urgently required.…”