Emerging Single-Atom Catalysts and Nanomaterials for Photoelectrochemical Reduction of Carbon Dioxide to Value-Added Products: A Review of the Current State-of-the-Art and Future Perspectives

Abstract

Rapid industrialization has resulted in a drastic increase in the consumption of natural resources, particularly fossil fuels. Fossil fuels in the form of coal, natural gas, oils, etc. have been extensively used to meet ever-increasing energy demands, resulting in adverse environmental effects. Massive fossil fuel consumption has led to enormous carbon dioxide (CO2) emissions, adversely impacting the environment through global warming. Photoelectrochemical (PEC) reduction of CO2 into valuable fuels, for instance, formic acid (HCOOH), methanol (CH3OH), ethanol (C2H5OH), etc., which combines the merits of both photochemical and electrochemical techniques, has been considered as a potential approach to address the issue of CO2 mitigation. Single-atom catalysts (SACs) along with emerging nanomaterials (NMTs) as photoelectrode composite materials present an effective avenue to augment PEC CO2 reduction owing to their well-defined structures and almost complete atom utilization. The present review focuses on the application of various SACs and NMTs as emerging photoelectrode materials that are advantageous for efficient PEC CO2 reduction to valuable fuels, such as HCOOH, CH3OH, C2H5OH, and carbon monoxide. The mechanism pertaining to the effective utilization of incident light energy to overcome the band gap and produce photogenerated charge carriers that contribute to the PEC reduction of CO2 has also been elucidated. At the outset, some challenges and opportunities that lie ahead in boosting SAC’s PEC performance have been discussed.