Photodeposition of CoO and MoS2 on CdS as dual cocatalysts for photocatalytic H2 production

Abstract

• Noble-metal-free CoO x and MoS 2 are applied as dual cocatalysts for CdS. • A two-step photodeposition strategy was used to deposit CoO x and MoS 2 on CdS. • In a photocatalytic process, MoS 2 and CoO x extract electrons and holes, respectively. • The synergistic effect between CoO x and MoS 2 obviously prolongs the lifetime of photoexcited charge carriers. • CoO x and MoS 2 significantly improve the H 2 -evolution activity of CdS by decreasing the charge recombination rates. Photocatalytic H 2 production from water splitting has a promising prospect for alleviating energy and environmental issues. However, the fast recombination of photogenerated charge carriers limits the photocatalytic efficiency and its practical application. Cocatalyst engineering is an effective strategy to spatially separate photogenerated charge carriers. In this work, noble-metal-free MoS 2 and CoO x cocatalysts are loaded on CdS nanorods by a two-step photodeposition method. The MoS 2 functions as the reduction cocatalyst to trap electrons and CoO x as the oxidation cocatalyst to trap holes. Transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS) and Mott-Schottky results demonstrate the effectiveness of photodeposition for loading MoS 2 and CoO x dual cocatalysts on CdS and their impact on the photochemical properties. The optimized CdS-MoS 2 -CoO x composite exhibits a high photocatalytic H 2 -production rate of 7.4 mmol g –1 h –1 and an apparent quantum efficiency (QE) of 7.6% at 420 nm. Further analysis on time-resolved photoluminescence (TRPL) indicates that the introduction of dual cocatalysts greatly prolongs the lifetime of photogenerated charge carriers and deceases the charge recombination rates, consequently leading to superior photocatalytic H 2 -production performance. This work provides a facile and effective strategy for the construction of highly efficient dual-cocatalyst-modified CdS photocatalyst for high-performance photocatalytic H 2 production.