Dual-metal co-catalyst integrated graphitic carbon nitride for photocatalytic hydrogen evolution reaction

Graphitic carbon nitride (g-C 3 N 4 ) nanosheets are extensively used in photocatalytic applications but are often decorated with noble-metal co-catalysts to yield relevant efficiencies. Herein, we report a dual-metal co-catalyst system comprising cobalt and molybdenum (CoMo) nanoclusters uniformly integrated into heptazine g-C 3 N 4 nanosheets for enhanced visible-light-driven hydrogen evolution reaction (HER). The intimate contact between metals as well as with gC 3 N 4 layer was verified through X-ray absorption and X-ray photoelectron spectroscopies. Mechanistic insights obtained through a combination of experimental and computational studies suggest that Co acts as primary catalytic center, while Mo plays a preliminary role in facilitating surface hydrogen coverage, collectively accelerating the redox rates and achieving 10 times higher performance compared to bare gC 3 N 4 . Post-HER analysis reveals disintegration of co-catalyst into Co single-atoms, which then takes the leading role in sustaining the HER. The role of co-catalyst was mainly limited to the surface, acting as electron trap, reducing charge recombination and as a HER catalytic center. The composite exhibits excellent photostability over 13 h of ON/OFF illumination cycles, highlighting its potential for intermittent operations under practical conditions. This study presents a co-catalyst design strategy leveraging dual-metal synergy as a non-noble, scalable alternative to conventional noble-metal-based HER co-catalysts for solar fuel generation.