Ultra-low content of Pt modified CdS nanorods: one-pot synthesis and high photocatalytic activity for H2 production under visible light

Abstract

Noble metal-modified CdS is one of the most promising photocatalysts for solar H₂ production due to its intrinsic band structure merits. It is highly desirable to develop an effective preparation route to pursue a high photocatalytic performance and to minimize the use of costly noble metals. For the first time, a simple and convenient one-pot solvothermal (OPS) method was developed to prepare platinized CdS nanorods (Pt/CdS-N) in this work. The formation of a hexagonal 1D structure CdS and the deposition of Pt(0) can be achieved simultaneously by the method, which is more efficient than the conventional post-deposition routes, such as photochemical reduction and impregnation–reduction methods, to enhance the photocatalytic activity of CdS-N for the H₂ evolution reaction (HER). The H₂ evolution rate (r_H2) of CdS-N could be remarkably improved from 2.10 to 10.29 mmol h⁻¹ g⁻¹ by loading with only 0.06% Pt (wt%) under visible light irradiation (λ > 400 nm, 300 W Xe lamp). No deactivation of the sample was observed in cyclic experiments for 20 h reaction. This loading amount of Pt is substantially lower than the reported optimal values (commonly in the range of 0.5–2%) by more than one order of magnitude. A criterion of enhancement coefficient was proposed to identify the ideal loading amount of Pt. The result indicates that, considering the improvement efficiency of r_H2 and the loading amount of Pt, this ultra-low amount of Pt is more practical than the optimal amount (determined to be 0.5%). The high and stable activity of Pt/CdS-N can be attributed to the hexagonal 1D structure of CdS and the high dispersion of Pt in the Pt(0) state. Besides Pt, the OPS method is also valid for the deposition of Pd or Ru on CdS and r_H2 decreases in the order Ru/CdS-N (12.89) > Pt/CdS-N (10.29) > Pd/CdS-N (6.72 mmol h⁻¹ g⁻¹) with a loading amount of 0.06%. It reveals that the use of noble metal co-catalysts can be significantly reduced without unduly sacrificing the HRE efficiency. The developed OPS route provides a new insight into the preparation of highly efficient and stable chalcogenide photocatalysts for the HER.