Cooperation of carbon doping and carbon loading boosts photocatalytic activity by the optimum photo-induced electron trapping and interfacial charge transfer

Abstract

Carbon-based materials with various advantages have gained growing research interests in photocatalytic field, in which, employing carbon materials as active catalysts presents new opportunities for low-cost, green and sustainable energy conversion strategic. The performance of these carbon-based photocatalyst highly depends on several factors, including photoexcitation, charge separation and transfer and surface catalytic reaction, and surface catalytic process for H2 production. Here, the graphitic carbon nitride (g-C3N4) system with doping carbon and loading carbon dots (CDs) was constructed via a direct thermal polymerization route to reveal the effect of trap states and displayed a 4-fold boosted H2 evolution efficiency relative to ordinary g-C3N4 during the photocatalysis. Transient absorption spectroscopy (TAS) results disclosed that the C-doping induced shallow trap states could capture photo-induced electrons to restrain deep trapping and direct recombination of photo-generated carriers. Density functional theory (DFT) calculation and transient photovoltage technique (TPV) test results confirmed that the fast holes’ transfer path established between CDs and C-doping g-C3N4 (CCN) make the CDs possess the extractive effect for the holes for the oxidation reaction with (TEOA), achieving spatial separation of electron-hole pairs. This study of interfacial charge transfer and transport dynamics provides a reference significance for the design and development of highly active carbon-based composite photocatalysts.