p–n Heterojunction Photocatalyst Mn0.5Cd0.5S/CuCo2S4 for Highly Efficient Visible Light-Driven H2 Production

It is highly important to develop efficient and cheap photocatalysts for hydrogen production. Herein, a series of p–n heterojunction Mn0.5Cd0.5S/CuCo2S4 has been successfully synthesized for the first time by the hydrothermal impregnation method. Mn0.5Cd0.5S/CuCo2S4 loading with 12 wt % CuCo2S4 shows the highest H2 evolution rate of 15.74 mmol h–1 g–1 under visible light (λ ≥ 420 nm) irradiation, which is about 3.15 and 15.28 times higher than that of bare Mn0.5Cd0.5S (4.99 mmol h–1 g–1) and CuCo2S4 (1.03 mmol h–1 g–1), respectively. In addition, it shows a relatively good stability during the five recycle tests, with about 20% loss of reaction rate compared to that of the first cycle. The superior photocatalytic performance is attributed to the effective separation and transfer of photogenerated charge carriers because of the formation of the p–n junction. The samples are systematically characterized by X-ray diffraction, ultraviolet–visible (UV–vis), diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, photoluminescence, EIS, and so on. UV–vis and EIS show that CuCo2S4 can effectively improve the visible light response of Mn0.5Cd0.5S/CuCo2S4 and promote the electron transfer from CuCo2S4 to the conduction band of Mn0.5Cd0.5S, so as to improve the photocatalytic efficiency. This study reveals that the p–n heterojunction Mn0.5Cd0.5S/CuCo2S4 is a promising photocatalyst to explore the photocatalysts without noble metals.