Boosting Photocatalytic H₂O₂ Fuel Cell Performance with Conjugated Graphite-Phase Carbon Nitride Decorated by Ag Nanoparticles

In this study, a Ag/CCN composite photocatalyst with a dragon-fruit section structure synthesized by loading silver nanoparticles (Ag NPs) onto CCN (g-C3N4 modified by M-phenylenediamine), is successfully employed as the photoanode in the H2O2 fuel cell system. Through the optimization of Ag NP loading amount, the 5%-Ag/CCN composite-based fuel cell exhibits a maximum power density of 1.195 mW·cm–2 in an aqueous solution containing 0.1 M HCl under AM 1.5G illumination (1 sun, 100 mW·cm–2), which is about 2.4 times higher than that of the g-C3N4-based fuel cell. The solar-to-electricity conversion efficiency (SECE) of the above fuel cell is further calculated to be 0.886%. Additionally, the 5%-Ag/CCN-based photocatalytic H2O2 fuel cell shows high stability during the charge and discharge process and strong energy storage capacity, along with a specific capacitance of 6860 mF·cm–2 after 2 h of irradiation and a capacitance retention rate of 60.33% even after 6 h of continuous operation. The localized surface plasmon resonance (LSPR) effect of Ag NPs significantly enhances the light capture capability of the photoanode, and the Schottky junction formed at the interface between Ag NPs and CCN effectively suppresses the recombination of photogenerated electrons and holes, promoting the photocatalytic oxidation of H2O to generate H2O2. This study provides a feasible strategy for constructing an efficient photoanode to generate H2O2, further improving the energy conversion efficiency and stability of H2O2 fuel cells.