Hollow CoS_<i>x</i> Polyhedrons Act as High-Efficiency Cocatalyst for Enhancing the Photocatalytic Hydrogen Generation of g-C₃N₄

Abstract

Seeking for a suitable cocatalyst to realize highly efficient photocatalytic hydrogen (H2) production is a great challenge in the field of solar energy conversion. Herein, hollow cobalt sulfide (CoSx) polyhedrons derived from ZIF-67 metal–organic frameworks were used as a cocatalyst to enhance the photocatalytic H2 generation performance of graphitic carbon nitride (g-C3N4). The polyhedral morphology with more exposed edges provides more surface active sites for H2 generation, while the interface between CoSx and g-C3N4 with intimate contact leads to better separation efficiency of photogenerated charge carriers. Moreover, the hollow structure not only favors mass diffusion/transfer, but also induces multiple reflections of light within the hollow cavity, enhancing the utilization efficiency of solar energy. As a result, the obtained CoSx/g-C3N4 composites showed excellent photocatalytic H2 generation activity, achieving a H2 evolution rate of 629 μmol g–1 h–1 under visible light (λ ≥ 400 nm), which was about 52 times higher than that achieved by pure g-C3N4. This work proves that hollow CoSx polyhedrons can be a potential substitute for noble metal cocatalysts for photocatalytic H2 generation.