Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO3 Photocatalyst

Abstract Overall water splitting (OWS) using semiconductor photocatalysts is a promising method for solar fuel production. Achieving a high quantum efficiency is one of the most important prerequisites for photocatalysts to realize high solar‐to‐fuel efficiency. In a recent study ( Nature 2020 , 58 , 411–414), a quantum efficiency of almost 100 % has been achieved in an aluminum‐doped strontium titanate (SrTiO 3 : Al) photocatalyst. Herein, using the SrTiO 3 : Al as a model photocatalyst, we reveal the criteria for efficient photocatalytic water splitting by investigating the carrier dynamics through a comprehensive photoluminescence study. It is found that the Al doping suppresses the generation of Ti 3+ recombination centers in SrTiO 3 , the surface band bending facilitates charge separation, and the in situ photo‐deposited Rh/Cr 2 O 3 and CoOOH co‐catalysts render efficient charge extraction. By suppressing photocarrier recombination and establishing a facile charge separation and extraction mechanism, high quantum efficiency can be achieved even on photocatalysts with a very short (sub‐ns) intrinsic photocarrier lifetime, challenging the belief that a long carrier lifetime is a fundamental requirement. Our findings could provide guidance on the design of OWS photocatalysts toward more efficient solar‐to‐fuel conversion.