C<sub>3</sub>N<sub>4</sub>/Se-CNTs as Advanced Metal-Free\nCatalysts for the Photoassisted Electrocatalytic Oxygen Evolution\nReaction

Photoassisted electrocatalysis is a frontier direction\nof electrocatalysis\nfor promoting energy conversion. In this work, a metal-free C<sub>3</sub>N<sub>4</sub>/Se-CNTs is reported as a novel catalyst for\nphotoassisted electrocatalytic oxygen evolution reaction (OER). C<sub>3</sub>N<sub>4</sub> has an appropriate bandgap, high specific surface\narea, and long-term stability. CNTs can modulate the electronic environment\nof C<sub>3</sub>N<sub>4</sub> by strong π–π interaction\nand greatly enhance the separation efficiency of photogenerated carriers.\nThe distributed Se nanoparticles in CNTs can further increase the\ncharge transfer ability. As a metal-free catalyst, the C<sub>3</sub>N<sub>4</sub>/Se-CNTs exhibits an overpotential of 231 mV at a current\ndensity of 10 mA cm<sup>–2</sup> and a small Tafel slope of\n52 mV dec<sup>–1</sup> under illumination, which ranks among\nthe best catalysts for photoassisted OER performance, surpassing most\nnoble and transition metal-based catalysts. The result demonstrates\nthe great potential of C<sub>3</sub>N<sub>4</sub>-based catalysts\nin the photoassisted OER process and provides a new perspective to\nexplore the excellent metal-free OER catalysts.