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 H2 evolution activity (738 μmol h−1 gcat−1; with 3 wt% Pt as the cocatalyst) and photocatalytic H2O2 production (3.94 mmol h−1 gcat−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 H2 evolution and O2 reduction reactions. Moreover, visual evidence of superior charge transport in the hybrid photocatalyst is revealed through the photodeposition of smaller Pt nanoparticles (∼7 nm) with uniform distribution on the carbon regions, which also accounts for the increased catalytic activity.