In-situ construction of CoS on porous g-C3N4 for fluent charge transfer in photocatalytic hydrogen production

Abstract

Constructing active sites with optimized surface interface structure on photocatalysts is essential to photocatalytic H2 production. Herein, CoS as a promising cocatalyst is in-situ anchored on the surface porous g-C3N4 (PCN) using a facial solid-state method. The in-situ growth of CoS with small particle size on PCN endows their intimate interfacial contact, which provides a fluent transfer channel of photogenerated carriers. CoS promotes photogenerated electron-hole pairs and reduces the overpotential of H2 evolution. According to the results of Density functional theory (DFT) calculations, benefitting from the difference of work functions between CoS and PCN, photogenerated electrons spontaneously migrate from PCN to CoS, thus resulting in the spatial separation of carriers. Moreover, CoS possesses near-zero ΔGH*, causing the electrons gathered on CoS to be more likely to reduce protons to H2 molecules. The apparent quantum efficiency (AQE) of hydrogen evolution on 2 % CoS/g-C3N4 at λ = 420 nm reaches 35.6 % and the maximum H2-evolving rate reaches as high as 3.27 mmol·h−1·g−1 under the irradiation of natural light. This work provides a facile synthesis method for loading metal sulfide cocatalysts and gains a deeper understanding of the mechanism of CoS acting as active sites for photocatalytic H2 production.