On factors limiting the performance of photoelectrochemical CO₂ reduction

The photoelectrochemical CO₂ reduction reaction (PEC-CO2RR) is a promising artificial photosynthetic system for storing solar energy as the energy of chemical bonds and stabilizing the atmospheric CO₂ level. An applicable PEC-CO2RR is expected to have broad light absorption, high selectivity to a single product, and high solar to fuel efficiency. However, the PEC-CO2RR still faces challenges from complex reaction pathways, obstructed mass transfer, and large photovoltage requirements. The goal of this perspective is to point out some of the limitations of PEC-CO2RR to a practical application. In brief, we discuss the basic concepts of PEC-CO2RR and summarize state-of-the-art progress. Moreover, we highlight the remaining challenges to both science and engineering and propose the key steps in developing a fully functional PEC-CO2RR system. Finally, an ideal PEC-CO2RR system is proposed for future studies, which is essentially wireless and combines the advantages of minimized polarization loss and broad light absorption.