Abstract
Electrochemical reduction of CO2 to fuels and chemical feedstocks using renewable electricity provides a promising approach toward artificial carbon recycling to address the global challenges in energy and sustainability. The most crucial step for this technique is to develop efficient electrocatalysts capable of reducing CO2 to valuable hydrocarbon products at a low overpotential with high selectivity and stability. In this article, we present a review on the recent developments and understanding of p-block post-transition metal (e.g., Sn, In, Pb, and Bi) based electrocatalysts for electrochemical CO2 reduction. This group of electrocatalysts shows particularly high selectivity for reduction of CO2 to formate or formic acid. Our main focus will be on the fundamental understanding of surface chemistry, active sites, reaction mechanism, and structure–activity relationships. Strategies to enhance the activity including morphology control, nanostructuring, defect engineering, doping, and alloying to modulate the electronic structure will also be briefly discussed. Finally, we summarize the existing challenges and present perspectives for the future development of this exciting field.
Highlights
Li and coworkers reported the tuning of Sn-based catalysts for the electrochemical CO2 reduction reaction (CO2RR) selectively toward CO or formate by controlling the thickness of the SnO2 layer coated on Cu nanoparticles: a thicker (1.8 nm) SnO2 layer shows Sn-like activity to generate formate, whereas the thinner (0.8 nm) shell is selective to the formation of CO with the conversion faradaic efficiency (FE) reaching 93% at −0.7 V vs reversible hydrogen electrode (RHE).[23]
We focus on the fundamental understanding of surface chemistry, active sites, and structure–activity relationships
Regarding the active sites for the CO2RR, a key observation is that the presence of metal oxide species on the catalyst surfaces under the electrochemical CO2RR conditions is crucial for the activity and selectivity of Sn and In based electrocatalysts
Summary
Since the industrial revolution in the nineteenth century, fossil fuels such as coal, petroleum, and natural gas have been exploited as the main energy source to sustain our economy and society. Metal-free carbon-based catalysts such as N-doped carbon nanotubes and N-doped fullerenes have been shown to drive the CO2 reduction preferentially toward formate.[36,37,38] the reported selectivities are generally lower than those of p-block metalbased catalysts, robustness and environmental friendliness are the desirable properties of these nonmetal catalysts These are materials of interest because formate (formic acid) is a highly valued product for many industrial processes. We summarize the existing challenges and present perspectives for the future development of this exciting field
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