Black Trumpet Mushroom-like ZnS incorporated with Cu3P: Noble metal free photocatalyst for superior photocatalytic H2 production

Abstract

The development of the efficient photocatalysts with improved photoexcited charge separation and transfer is an essential for the effective photocatalytic H₂ generation using light energy. So far, owing to the unique properties and characteristics, the transition metal phosphides (TMPs) have been proven to be high performance co-catalysts to replace some of the classic precious metal materials in the photocatalytic water splitting. In the present work, we report a novel copper phosphide (Cu₃P) as a co-catalyst to form a well-designed fabricated photocatalyst with blacktrumpet mushroom-like ZnS semiconductor for the first time. The synthesis of Cu₃P/ZnS consists of two-step hydrothermal and ball milling methods. The physical properties of the materials so prepared were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. In order to study the role of Cu₃P, electrochemical impedance spectroscopy (EIS) measurements were used to investigate the photogenerated charge properties of ZnS. The experiments of photocatalytic production of H₂ confirm that the Cu₃P co-catalysts effectively promote the separation of photogenerated charge carriers in ZnS, and consequently enhance the H₂ evolution activity. The 3% Cu₃P/ZnS sample delivers the highest catalyst activity and the consistent H₂ evolution rate is14,937 µmol h^-1 g^-1_cat, which is 10-fold boosted compared to the pristine ZnS. The stability of the catalyst was tested by reusing the used 3% Cu₃P/ZnS photocatalyst in five consecutive runs, and their respective activity in the H₂ production activity was evaluated. A possible mechanism is proposed and discussed.

Keywords: Charge carriers separation; Cu(3)P; Hole trapper; Hydrogen generation; ZnS; co-catalyst; p-n heterojunction.