Constructing Heterojunction Photocatalyst Systems with Spatial Distribution of Au Single Atoms for CO₂ Reduction

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.