Nanoengineering of metal-based electrocatalysts for carbon dioxide (CO2) reduction: A critical review

Massive carbon dioxide (CO2) emissions from the extravagant use of traditional fossil fuels and heavy anthropogenic activities have been the predominant causes of present-day global warming and climate change. Electrocatalytic CO2 reduction reaction (eCO2RR), typically in the aqueous phase, is regarded as a sustainable strategy to transform CO2 into value-added chemical compounds (e.g., precious hydrocarbons and oxygenates), thus addressing the global concerns of non-renewable energy sources (e.g., fossil fuels) depletion and ever-increasing environmental pollution simultaneously. Nevertheless, due to the slack kinetics of eCO2RR and inevitable undesired side reactions (e.g., hydrogen evolution reaction; HER), highly active, selective, and stable electrocatalysts are crucially demanded to promote this thermodynamically uphill reaction. Metal-based nano-materials have proven promising prospects among various electrocatalysts used for eCO2RR due to their ease of synthesis, high activity, and resource abundance. While copper (Cu)-based electrocatalysts are typical choices for the C-C coupling and thus generation of multicarbon (C2+) chemicals (e.g., ethylene (C2H4) and ethanol (CH3CH2OH)), other transition metal (TM)-based catalysts such as tin (Sn), zinc (Zn), silver (Ag), and their oxides are often utilized for producing light and monocarbon products (e.g., carbon monoxide (CO), formate (COOH-), methane (CH4), and methanol (CH3OH)). This review highlights the contemporary advancements in materials and nanoengineering strategies for exploring potential metal-based catalysts for efficient eCO2RR. In the meantime, challenges in obtaining a highly selective and stable electrocatalyst will be discussed. Recent efforts toward addressing the stability-and selectivity-related issues will also be presented in detail.