Hollow CoSx Polyhedrons Act as High-Efficiency Cocatalyst for Enhancing the Photocatalytic Hydrogen Generation of g-C₃N₄

Seeking for a suitable cocatalyst to realize highly efficient photocatalytic hydrogen (H 2 ) production is a great challenge in the field of solar energy conversion. Herein, hollow cobalt sulfide (CoS x ) polyhedrons derived from ZIF-67 metal–organic frameworks were used as a cocatalyst to enhance the photocatalytic H 2 generation performance of graphitic carbon nitride (g-C 3 N 4 ). The polyhedral morphology with more exposed edges provides more surface active sites for H 2 generation, while the interface between CoS x and g-C 3 N 4 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 CoS x /g-C 3 N 4 composites showed excellent photocatalytic H 2 generation activity, achieving a H 2 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-C 3 N 4 . This work proves that hollow CoS x polyhedrons can be a potential substitute for noble metal cocatalysts for photocatalytic H 2 generation.