Work-Function Induced Gradient-Driven Charge Steering in Pt Nanoparticles on Modified B/S/Cu-Doped g-C3N4 for Highly Selective Nitrate Photoreduction to Ammonia

Photocatalytic nitrate reduction to ammonia (NO3−RR) represents an appealing approach for simultaneous aqueous remediation and sustainable ammonia synthesis. However, its practical efficacy is limited by sluggish multi-electron-transfer kinetics and the competitive hydrogen evolution reaction. Herein, we report a synergistic nanostructured catalytic architecture comprising B/S/Cu-co-doped polymeric carbon nitride (g-C3N4) nanosheets decorated with Pt nanoparticles (B/S/Cu−CN + Pt). Structural characterizations indicate that B/S/Cu co-doping narrows the bandgap of g-C3N4 and significantly increases the specific surface area. Kinetic investigations demonstrate high interfacial charge separation and migration efficiencies. Ultraviolet photoelectron spectroscopy elucidates a substantial chemical potential gradient between B/S/Cu−CN nanosheets (work function = 3.27 eV) and Pt nanoparticles (work function ≈ 5.7 eV). This potential gradient drives spontaneous electron transfer from the B/S/Cu−CN conduction band to the Pt active centers to achieve Fermi-level equilibration, thereby constructing a highly efficient interfacial charge-steering channel. Spectroscopic analyses support the metallic Pt0 nature of the anchored Pt nanoparticles. Under optimal conditions, the B/S/Cu−CN + Pt nanostructured catalyst achieves a remarkable ammonia yield rate of 2231.7 μmol h−1 g−1 with high product selectivity. This work presents a work function-induced charge-steering mechanism, providing valuable insights into designing high-performance, multi-component synergistic photocatalytic systems for nitrogen cycling.