A novel noble-metal-free FeS2/Mn0.5Cd0.5S heterojunction for enhancing photocatalytic H2 production activity: Carrier separation, light absorption, active sites

Abstract

Background

The development of efficient and noble-metal-free photocatalysts is greatly essential for photocatalytic hydrogen production. However, the photocatalytic activity of a single photocatalyst is usually limited for various reasons.

Methods

Herein, FeS₂/Mn_0.5Cd_0.5S (FSMCS) heterojunctions were constructed by a simple solvent evaporation method. The morphological characterizations revealed a raspberry-like hollow microsphere structure for FeS₂ and irregular granularity for Mn_0.5Cd_0.5S. Photoluminescence (PL) and electrochemical experiments indicated that the FSMCS composite effectively facilitated the separation of photogenerated electron-hole pairs. The UV–vis diffuse reflectance spectrum (DRS) showed that, in FSMCS composite, the visible light absorption range was effectively expanded to the full visible light.

Significant findings

Excellent photocatalytic activity in FSMCS heterojunctions without loading noble metals because FeS₂ could serve an active site for hydrogen production. The optimum FSMCS composite had excellent photocatalytic hydrogen production activity (6.1 mmol·g⁻¹·h⁻¹), which was 5.6 and 2.3 times higher than that of the pristine Mn_0.5Cd_0.5S (1.1 mmol·g⁻¹·h⁻¹) and Mn_0.5Cd_0.5S-1 %Pt (2.7 mmol·g⁻¹·h⁻¹). Meanwhile, in four round-robin tests, the activity of the 5FSMCS photocatalyst did not significantly decrease. This work proved that combining Mn_0.5Cd_0.5S and non-precious metal cocatalysts to construct heterojunctions is a promising strategy for photocatalytic hydrogen production.