Determining the properties of photocathodes for photoelectrochemical CO₂ reduction: A brief overview

Billions of tons of carbon dioxide (CO2) are released into the atmosphere each year due to the use of fossil fuels. As a result, people are seeking ways to convert CO2 into high-value chemicals. Among various strategies, pho-toelectrochemical (PEC) process is considered as an effective way with unique advantages. In the last decade, various photocathodes have been designed to improve the performance of PEC CO2 reduction reaction (CO2RR). In order to improve the photocathodes performance in a more guided manner, a thorough understanding of the photocathode properties is necessary. In this review, the semiconductor characterization methods are firstly presented, including determining the band structure of the photocathode and studying the carrier transport behavior. Following this, a detailed discussion of the PEC performance is summarized, including light harvesting efficiency, photogenerated charge separation efficiency and catalysis efficiency. Furthermore, the PEC CO2RR mechanism illustrated through in situ characterization techniques analysis is also outlined. Finally, a brief conclusion and outlook are presented.