Artificial photosynthesis is considered a promising method for achieving carbon-neutral targets. The hydrogen evolution reaction (HER) from the photoelectrolysis of water and the photoelectrochemical (PEC) CO2 reduction have gathered significant attention as an effective way to store intermittent solar energy in fuels and chemicals, as well as closing the chemical carbon cycle. In this approach, light absorbers, catalysts, contacts, and interfaces with the electrolyte need to work together to efficiently convert reactants into products. Also the interactions between the reactants with the catalytic surface of the (photo)electrocatalytic device is of primary importance to determine the selectivity and activity of the device. Unfortunately, these devices are often unstable or exhibit insufficient activity or selectivity for the CO2 reduction reaction (CO2RR). In addition to the thermodynamic requirements, the semiconductor/electrolyte interface also plays a crucial role in determining the performance of photoelectrodes, directly influencing the efficiency and performance of artificial photosynthetic systems.
In this context, we present a few examples of how light-absorbing materials can be utilized in integrated photoelectrochemical cells or when directly interfaced with the electrolyte for HER and CO2RR. The talk will span metal oxide materials, silicon, and halide perovskites. We will also look into modification of the local catalytic environment to address selectivity issue in photoelectrochemical CO2 reduction. Our approach demonstrates that the mechanistic understanding of these complex systems can lead to improved stability and performance of various photoelectrode materials used in these reactions.