Dopant-Induced Edge and Basal Plane Catalytic Sites on Ultrathin C3N4 Nanosheets for Photocatalytic Water Reduction

The emerging carbon nitride (C3N4) offers a serious possibility for realizing a highly effective hydrogen evolution reaction (HER). However, their insufficient catalytic sites and poor conductivity hamper the HER performance. Herein, an oxygen, phosphorus dual-doped ultrathin C3N4 nanosheet (O, P-CNS) is synthesized through a two-step method without a liquid solution, including calcination under air and subsequent chemical vapor deposition (CVD) with sodium hypophosphite (NaH2PO2) in N2 atmosphere. The first thermal treatment in the air atmosphere results in the introduction of O dopant on the edge of C3N4 and the exfoliation of bulk C3N4 into ultrathin nanosheets. The following P incorporation contributes to the activation of the basal plane of C3N4 and the improvement of the intrinsic electronic conductivity, thus giving rise to the facilitated H2 generation rate. Particularly, a superior H2 generation rate of 8.7 mmol g–1 h–1 under visible light and an apparent quantum yield of 23.65% with 420 nm could be realized after the two-step dual-doping-induced calcination, further confirming the enhanced charge separation with the full activation of the edge and basal plane catalytic sites of C3N4. Our work on dual-doping-induced catalytic site activation on the edge and basal plane of C3N4 will provide more guidance in the field of designing C3N4-based photocatalysts.