Binary junctions enhance electron storage and potential difference for photo-assisted electrocatalytic CO2 reduction to HCOOH

Photo-assisted electrocatalytic (PAEC) CO2 conversion is a crucial approach for achieving sustainable carbon neutrality. Here, we have developed a binary-junctions photoanode by integrating SrTiO3 and anatase-rutile TiO2 nanotube arrays (STO/A-R TNTAs), which exhibits exceptional activity and selectivity in converting CO2 to HCOOH. The synergetic effects of the SrTiO3/TiO2 heterogeneous junction and the anatase-rutile TiO2 heterophase junction effectively facilitate photoelectron separation and storage, leading to a potential difference between anode and cathode. The establishment of the electron storage strategy, triggered by hetero- junction/phase interfaces, serves as remarkably efficient electron trapping regions with dam-like characteristics. As a result, the STO/A-R TNTAs achieves a generation rate of 68.24 μmol cm−2 h−1 with 92.25% selectivity and 90.70% Faradic efficiency. This performance is approximately 8 times higher compared to the pristine TiO2 nanotube arrays photoanode. The implementation of the electron storage mechanism presents a promising approach to improve CO2 reduction activity and selectivity.