Salt-Assisted Synthesis of 3D Porous g-C3N4 as a Bifunctional Photo- and Electrocatalyst.

Graphitic carbon nitride (g-C3N4), characterized with a suitable bandgap, has aroused great interest as a robust and efficient catalyst for solar energy utilization. Herein, we introduce a new strategy to fabricate a three-dimensional (3D) porous g-C3N4 by a facile NaCl-assisted ball-milling strategy. The porous structure-induced advantages, such as a higher specific surface area, more efficient charge separation, and faster electron-transfer efficiency, enable the 3D porous g-C3N4 to achieve impressive properties as a bifunctional catalyst for both photocatalytic hydrogen evolution and electrocatalytic oxygen evolution reaction (OER). As a result, the 3D porous g-C3N4 exhibits a hydrogen evolution rate of 598 μmol h-1 g-1 with an apparent quantum yield of 3.31% at 420 nm for photocatalytic H2 generation, which is much higher than that of the bulk g-C3N4. Simultaneously, the porous g-C3N4 also presents an attractive OER performance with a low onset potential of 1.47 V (vs reversible hydrogen electrode) in an alkaline electrolyte after rational cobalt-doping. Accordingly, the NaCl-assisted ball-milling strategy paves the way to the rational design of a controllable porous structure.