Integrating Cooperative Dual Active Sites Onto a Plasmonic Photocatalyst for Synergistic Promotion of the Reduction and Oxidation Half-Reactions in Ammonia Synthesis

Photocatalytic N₂ fixation offers a promising sustainable alternative to the energy-intensive Haber-Bosch process. Since N₂ fixation involves the reduction and oxidation half-reactions, understanding their synergistic relationship and achieving their cooperation is crucial for improving the overall efficiency of N₂ fixation. To fulfill this objective, we have designed a type of Ru-WO_{3- x}/CoO_x photocatalyst with respective reduction and oxidation active sites. In this type of photocatalyst, Ru doping not only provides reduction sites to facilitate N₂ adsorption and activation but also optimizes the band structure by widening the defect band and elevating the Fermi level. Meanwhile, the CoO_x clusters serve as O₂ evolution sites that can accelerate hole utilization and improve electron-hole separation, thereby enhancing N₂ reduction. Consequently, the Ru-WO_{3- x}/CoO_x photocatalyst gives an impressive NH₃ production rate of 131.95 µmol g^-1 h^-1 in pure water, superior to the photocatalysts with a single type of active site. The optimized catalyst delivers a solar-to-chemical conversion efficiency of 0.22% under AM 1.5G light illumination and maintains an apparent quantum efficiency above 0.2% within the entire test range, including the near-infrared region. This work underscores the mutual influence of the oxidation and reduction half-reactions in photocatalysis and highlights the cooperation between redox-active sites.