Enhanced solar hydrogen production by template-free oxygen doped porous graphitic carbon nitride photocatalysts

Abstract

In this work, a new strategy has been developed to synthesis template-free porous oxygen doped g-C3N4 nanorods by sulfur–assisted ultrasound followed by thermal polymerization method. As a result of a highly porous g-C3N4 nanorod (CNRS) with a surface area of 62 m2/g was observed, which is a factor of ∼3 times higher than bulk g-C3N4 (CNB). Importantly, N–O and an increased number of C=O bonds were observed in CNRS after sulfur-assisted treatment due to oxygen doping. Further, in-situ deposition of Pt has suppressed N–O and C=O bonds by forming divalent Pt, which could favor fast charge carrier transport. This proved by time-resolved photoluminescence measurement where relaxiation time of charge carrier in shallow-trap and deep-trap states significantly reduced to 2.1 and 8.5 ns respectively. As a result, a maximum H2 production rate of 5.5 mmol/h/g is achieved in solar light, which is ∼30 times higher than CNB. This significant enhancement in photocatalytic performance is owing to superior visible region harnessing properties, large specific surface area, and high porosity in oxygen doped porous g-C3N4 nanorods. We report, simple strategy and a new path for an effective designing of porous g-C3N4 nanorod photocatalyst by template-free and non-hazardous chemicals.