Metal-induced Z-scheme CdS/Ag/g-C3N4 photocatalyst for enhanced hydrogen evolution under visible light: The synergy of MIP effect and electron mediator of Ag

Abstract

Efficient photogenerated charge carriers separation and wide absorption wavelength range are important factors for improving photocatalytic performance and application potential of photocatalysts. Applying metal-induced photocatalysis and Z-scheme photocatalysis are two efficient ways to achieve the above aims. Herein, a metal-induced Z-scheme CdS/Ag/g-C3N4 photocatalyst was prepared for photocatalytic H2 evolution under visible light irradiation. X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM), high resolution field emission scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance (UV–vis DRS), photoluminescence spectrum (PL), transient photocurrent and electrochemical impedance spectroscopy (EIS) were performed to characterize the structures, optical and electrochemical properties. Results demonstrated that CdS/Ag/g-C3N4 (Ag 3 wt%, g-C3N4 15 wt%) exhibited superior photo-response performance and more efficient photogenerated carriers separation, compared to the counterparts. Owing to the desired properties of CdS/Ag/g-C3N4, high H2 evolution rate of 1376.0 μmol /h∙g in lactic acid scavenger solution was achieved, which was 3.12 and 1.76 times of those of CdS and CdS/g-C3N4. The roles of Ag on CdS/Ag/g-C3N4 were discussed, and it was believed that both metal-induced surface plasmon resonance effect and the Z-scheme electron mediator mechanism synergistically contributed to the enhanced performance. Possible mechanisms for photoelectrons transfer and photocatalytic H2 evolution were proposed.