Abstract
Photo-assisted electrochemical systems present a sustainable pathway for water splitting and metal–air batteries, yet their performance is hindered by poor visible- light utilization, short carrier lifetimes, and sluggish redox kinetics. This work introduces a novel concept of a plasmon-enhanced Mott–S-scheme heterojunction AgCo-Fe2O3/g-C3N4, designed to overcome these limitations through a synergistic integration of photonic and plasmonic mechanisms. Nitrogen-deficient g-C3N4(g- CN) acts as a light-harvesting scaffold, while coupling with Fe2O3 forms an S-scheme junction enabling directional charge migration and selective carrier separation. AgCo nanoparticles introduce localized surface plasmon resonance, simultaneously serving as electron sinks to suppress recombination and as hot-carrier generators that accelerate catalytic turnover. Collectively, these structural and electronic synergies lead to significantly enhanced activity with reduced overpotentials of 78 mV for HER and 174 mV for OER at 10 mA/cm2, and a half-wave potential of 0.855 V vs. RHE for ORR in alkaline media; outperforming commercial Pt/C and IrO2 references. Durable operation is demonstrated in industrial-level water splitting (500 and 1000 mA/cm2 for 120 h) and extended Zn-air battery cycling (>100 h). Altogether, these findings highlight a mechanistically guided approach to plasmonic Mott–S-scheme heterojunction design, enabling light-assisted redox catalysis across multiple reaction pathways.