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.

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“…C and O in the resulting chemicals in eq are commonly 1 to 3 (C 1 –C 3 products) and 0 to 2, respectively. The chemical products could be obtained on various transition-metal-based catalysts, metal–organic frameworks, organic mediators, MXenes, or carbon-based materials. ,,− …”

Toward Practical Li–CO2 Batteries: Mechanisms, Catalysts, and Perspectives

“…In principle, the more stable a bond, the greater the amount of energy that is required to break it. Therefore, direct CO 2 reduction is inevitably accompanied by a large amount of energy input in spite of the adoption of high-efficacy catalysts. − Benefiting from the superior reducibility of Li metal, it can extract oxygen atoms from CO 2 molecules. Meanwhile, the Li-driven CO 2 reduction reaction can proceed spontaneously and release energy.…”

Insights and Progress on Photocatalytic and Photoelectrocatalytic Reactor Configurations and Materials for CO2 Reduction to Solar Fuels

“…These outstanding attributes make PEC technology exhibit remarkable application potential toward efficient CO 2 utilization. Extensive reviews on the PC and/or PEC CO 2 reduction into value-added products were also presented by Wu et al, Castro et al, Pawar et al, Zarei and Ojani, Zhong et al., Verma et al, Wang et al, and Ding et al…”