In single-atomic photocatalyst systems, the spatial distribution of single atoms on heterojunctions and its impact on photocatalytic processes, particularly on carrier dynamics and the CO2 reduction process involving multielectron reactions, remains underexplored. To address this gap, a WO3/TiO2 nanotube heterojunction with a spatially selective distribution of Au single atoms was developed using an oxygen vacancy anchoring strategy for CO2 photoreduction. By anchoring Au atoms onto the WO3 or TiO2 components, a substantial number of active sites are generated and the electron transfer pathways from the heterojunction toward Au sites are formed, thereby enhancing carrier separation and concentration. As a result, the total yield of CO2 reduction products increases by 6.3 times and 3.9 times, respectively. More importantly, due to significant differences in adsorption properties, energy band structures, and reaction energy barrier, as well as a 2-fold difference in carrier lifetime, the selective distribution of Au single-atom sites results in completely different CO2 photoreduction products: when Au atoms are anchored on WO3 and TiO2 components, the product selectivity is 67.6% CH4 and 82.9% CO, respectively. This study clarifies the vital role of the spatial distribution of single atoms on the selectivity of electron-demanding products.
Keywords: CO2 reduction; WO3/TiO2 heterojunction; oxygen vacancies; photocatalysis; single-atom catalysis; spatial distribution..