Designing CdS-Based Ternary Heterostructures Consisting of Co-Metal and CoO_<i>x</i> Cocatalysts for Photocatalytic H₂ Evolution under Visible Light

Abstract

Heterostructure formation is an effective method used for designing photocatalysts that solve problems caused by photoexcited charge recombination phenomena associated with the photocatalytic water redox reaction. This work reports a new Co-metal-incorporated ternary heterostructured photocatalyst, CdS/CoO_<i>x</i>/Co-metal, which enhanced charge separation to increase photocatalytic H₂ evolution 30.5-fold in comparison to pure CdS under visible light. This work demonstrates for the first time the effect of the Co metal on photocatalytic H₂ evolution using the CdS/CoO_<i>x</i>/Co-metal ternary heterostructure. In the ternary heterostructure, Co metal and CoO_<i>x</i> act as photogenerated electron- and hole-capturing cocatalysts, respectively. Results from photoelectrochemical studies along with photocatalytic H₂ evolution data proved the enhancement of charge transfer and separation in the CdS/CoO_<i>x</i>/Co-metal heterostructure due to the addition of Co metal and CoO_<i>x</i>. Hence, the synergistic charge separation improvement achieved by the combination of CoO_<i>x</i> and the Co metal with CdS produced a photocatalytic H₂ evolution rate of 9.54 μmol/h, which is the highest reported H₂ evolution rate for a CdS-based system under l sun solar irradiance (>420 nm) to the best of our knowledge.