Atomic-scale mechanisms of enhanced photocatalytic hydrogen evolution in Mg/Zr-doped Ta₃N₅

Mg-Zr co-doping in Ta₃N₅ suppresses intrinsic defects, significantly enhancing the photocatalytic hydrogen production performance via water splitting. However, the microscopic mechanisms linking Mg/Zr dopants to carrier separation, Pt co-catalyst dispersion, and surface reactions remain unclear. Here, using first-principles calculations, we elucidate the individual and synergistic roles of Mg and Zr in improving the photocatalytic performance of Ta₃N₅ for hydrogen evolution from water splitting. Mg and Zr doping facilitates carrier separation, compensates for intrinsic defects through charge compensation, and increases carrier concentration. Critically, the coupling of Mg with oxygen impurities modulates the surface electronic structure, promoting Pt dispersion, while Zr coupling with oxygen impurities modifies Pt single-atom electronic states, reducing the hydrogen evolution reaction energy barrier. The synergy between Mg-Zr co-doping and oxygen impurities maximizes the hydrogen evolution rate. This work resolves the debate on the mechanisms of Mg/Zr doping in Ta₃N₅, providing theoretical insights and design principles for efficient and stable photocatalytic systems.