Rational design of a carbon/potassium poly(heptazine imide) heterojunction for enhanced photocatalytic H₂ and H₂O₂ evolution

We present the rational design of carbon/potassium poly(heptazine imide) (KPHI) heterostructures via one-step salt-melt assisted condensation for efficient photocatalysis. Hybridizing KPHI with an adenine-derived carbonaceous material (Ad-carbon) displayed an outstanding photocatalytic H-2 evolution activity (738 mu mol h(-1) g(cat)(-1); with 3 wt% Pt as the cocatalyst) and photocatalytic H2O2 production (3.94 mmol h(-1) g(cat)(-1)). We establish that the Ad-carbon simultaneously operates as an electron acceptor and a photosensitizer based on structural, optical and photo(electro)chemical characterization. Building an intimate heterojunction between the Ad-carbon and KPHI induced spatial charge separation and prolonged the carrier lifetime. From electrocatalysis, we confirmed that coupling Ad-carbon with KPHI enhanced the surface reaction kinetics towards H-2 evolution and O-2 reduction reactions. Moreover, visual evidence of superior charge transport in the hybrid photocatalyst is revealed through the photodeposition of smaller Pt nanoparticles (similar to 7 nm) with uniform distribution on the carbon regions, which also accounts for the increased catalytic activity.