CdTe/CdSe-sensitized photocathode coupling with Ni-substituted polyoxometalate catalyst for photoelectrochemical generation of hydrogen

In terms of photoelectrochemical (PEC) hydrogen evolution, substantial challenge still remains regarding the controllable fabrication of quantum dots (QDs)-sensitized photocathodes with enhanced visible-light absorption, efficient charge carrier separation, and directional migration at the electrode interface. In this work, the CdTe/CdSe QDs-sensitized photocathodes were delicately constructed on p-type NiO-coated indium tin oxide (ITO) electrodes by spin-coating approach. The resulting co-sensitized photocathode exhibits a favorable pseudo-Type II energetic band alignment that combines the advantages of strong light absorption of constituent QDs as well as the effective and oriented charge separation and migration. Upon green LED light illumination, the photogenerated electrons could be effectively transferred to a tetra-nickel-substituted polyoxometalate catalyst for hydrogen production while photogenerated holes will be scavenged at the NiO/ITO electrode. Under minimally optimized conditions, the pseudo-Type II CdTe/CdSe-sensitized photocathode yields a photocurrent density of over 100 µA/cm² and a Faradaic efficiency of ∼ 100%, which is among one of the most efficient QDs-based photocathode systems coupling with Ni-substituted polyoxometalate catalyst for photoelectrochemical hydrogen generation. [Figure not available: see fulltext.]