Photoelectrochemical CO2 Reduction: The Spotlight on The Light Absorber

Light-driven CO2 reduction into chemicals is considered as a promising way to meet carbon neutral targets. Photoelectrochemical (PEC) CO₂ reduction has attracted significant attention as a prevailing way to store intermittent solar energy in fuels and chemicals as well as closing the chemical carbon cycle. Unfortunately, thermodynamically viable photocathode materials for this process favor hydrogen evolution reaction (HER), thus leading to either insufficient activity or selectivity for CO2 reduction reaction (CO2RR). Besides the thermodynamic requirement, the semiconductor/electrolyte interface also plays a pivotal role in defining the performance of photoelectrodes, which can directly affect light driven CO2RR efficiency and determine the product selectivity.<br/>Here, we show few examples of how light absorber materials can be used in integrated photoelectrochemical cells or when directly interfaced with the electrolyte for CO2RR. Specifically, we show how one can improve the stability and performance of photoelectrodes for PEC CO2R in systems that use Cu₂O or halide perovskite materials. In addition, we will discuss how ZnTe can enable photo-generated charge carrier transfer, but also acted as electrocatalyst for boosting carbon product selectivity and suppressing HER. Our work demonstrates that the fundamental understanding of the processes at the photoelectrode/electrolyte interface allows the systematic improvement of photoelectrode stability of CO2RR selectivity.