Ag-TiO₂ nanocomposites enable efficient photocatalytic NH₃ synthesis by modulating electronic metal-support interaction

In the heterogeneous catalytic system of photocatalysis, the interface between the active metal and the semiconductor support is crucial in the catalytic process. Especially, the oxygen vacancies at the interface of metal oxide carriers have a huge impact on the reaction performance. Here, we researched the influence of the interfacial electronic interaction strength between the active metal and the semiconductor support on the performance of photocatalytic nitrate reduction for ammonia (NH₃) synthesis. The experimental results show that TiO₂ with low oxygen vacancy density (OVs) has a strong interfacial electronic interaction with the Ag nanoclusters (Ag-TiO₂), demonstrating a relatively high NH₃ yield rate of 2.31 mmol g-1h-1. Mechanistic studies reveal that the creation of OVs induces a structural transition on the TiO₂ surface from an ordered to a disordered state. This surface structural disorder weakens the interfacial electronic interaction between the Ag nanoclusters and the TiO₂ substrate (Ag-TiO_2-x). This attenuated interaction reduces the local electron density on TiO₂ and OVs act as electron traps to capture the plasmon-induced electrons injected from Ag nanoclusters, collectively impairing charge separation and transfer efficiency in Ag-TiO_2-x. As a result, Ag-TiO₂ possesses superior photoinduced charge carrier separation efficiency compared to Ag-TiO_2-x. These findings provide new insights into the interplay among metals, supports, and defects, offering important guidance for the sensible development of highly efficient supported catalysts.