Morphology and defects design in g-C3N4 for efficient and simultaneous visible-light photocatalytic hydrogen production and selective oxidation of benzyl alcohol

Abstract

Small surface area, deficient reaction sites, and poor visible-light harvest ability of the original graphitic carbon nitride (g-C3N4) severely restrict its photocatalytic H2 production activity. Here, an ultrathin porous and N vacancies rich g-C3N4 (VN-UP-CN) was fabricated by thermal oxidation exfoliation and high-temperature calcination under the Ar atmosphere. The ultrathin porous morphology increases the surface area and reaction sites of original g-C3N4, moreover, the produced N vacancies greatly broaden the light harvest ability of ultrathin porous g-C3N4 (UP–CN). Therefore, VN-UP-CN displays the maximal H2 production rate of 2856.7 μmol g−1 h−1 in triethanolamine solution under visible-light, and adding 0.5 M of K2HPO4 can further improve its H2 production rate to 4043.9 μmol g−1 h−1. Importantly, VN-UP-CN also shows good performance in simultaneous photocatalytic H2 production and benzyl alcohol oxidation to benzaldehyde with the activities of 196.08 and 198.28 μmol g−1 h−1, respectively, which avoids the waste of sacrificial agent and photogenerated holes. This work affords an achievable way to design the efficient g-C3N4 photocatalyst by morphology and defect regulation, which can effectively utilize both photogenerated electrons and holes for H2 and value-added chemical production.