Light-modulated redox site switching in PCN: Achieving overall water splitting

Polymeric carbon nitride (PCN) has emerged as a promising photocatalytic material, yet its redox site dynamics under varying light sources remain poorly understood. In this study, we employ Kelvin probe force microscopy (KPFM) and in situ photo-deposition of a co-catalyst to reveal light-induced shifts in PCN’s oxidation and reduction sites, demonstrating that these sites are not fixed but dynamically reconfigured under different irradiation conditions. Theoretical calculations further support this observation, showing that excitation wavelength influences charge distribution within the PCN framework. Building upon these findings, we establish a sequential co-catalyst loading strategy: visible light irradiation selectively reduces platinum (Pt) onto PCN, while subsequent simulated sunlight exposure facilitates site-specific oxidation, forming both reduction and oxidation co-catalysts in situ. This strategy enables sustained photocatalytic water splitting, achieving stoichiometric H₂ and O₂ production in pure water. By elucidating the interplay between light wavelength and redox site reversibility, our findings challenge conventional assumptions of static active sites and offer a new framework for designing light-responsive photocatalytic systems for sustainable hydrogen and oxygen production.