Toward High-Efficiency Photovoltaics-Assisted Electrochemical and Photoelectrochemical CO2 Reduction: Strategy and Challenge

The realization of a complete techno-economy through a significant carbon dioxide (CO2) reduction in the atmosphere has been explored in various ways. CO2 reduction reactions (CO2RRs) can be induced using sustainable energy, including electric and solar energy, using systems such as electrochemical (EC) CO2RR and photoelectrochemical (PEC) systems. This study summarizes various fabrication strategies for non-noble metal, copper-based, and metal-organic framework-based catalysts with excellent FE for target carbon compounds, and for noble metals with low overvoltages. Even though EC and PEC systems exhibit high energy-conversion efficiency using excellent catalysts, they are not completely bias-free operations because they require external power. Therefore, photovoltaics, which can overcome the limitations of these systems, have been introduced. The utilization of silicon and perovskite solar cells for photovaltaics-assisted EC (PV-EC) and photovaltaics-assisted PEC (PV-PEC) CO2RR systems are cost efficient, and the III-V semiconductor photoabsorbers achieved high solar-to-carbon efficiency. This review focuses on all the members composed of PV-EC and PV-PEC CO2RR systems and then summarizes the special cell configurations, including the tandem and stacked structures. Moreover, current problems such as a low energy conversion rate, expensive PV, theoretical limitations, and scale-up to industrialization are discussed with the suggested direction.