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

Abstract

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 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 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.