ZnTe-based photocathode for hydrogen evolution from water under sunlight

Abstract

Zinc telluride (ZnTe)-based photocathodes with appropriate modifications showed incident-photon-to-current conversion efficiencies (IPCEs) higher than 30% at 420-520 nm, reached 40% IPCE at 460 nm, and were not zero up to 710 nm because of photoexcitation related to the intermediate-band. ZnTe films were prepared by productive close-spaced sublimation. After surface modification with CdS and Pt, the photocathode showed clear cathodic photoresponse in the phosphate buffer solution. The modulation of substrate temperature, incorporation of Cu, and further surface modification with very thin Mo and Ti layers significantly enhanced cathodic photocurrent which contributes to hydrogen evolution from water. Through the measurement of IPCEs, photoelectrochemical hydrogen evolution from water utilizing photoexcitation related to the intermediate-band was first confirmed. The photocathode showed advantageous durability under simulated sunlight: during irradiation of about 50 min, the stabilized photocurrent slightly decreased from 1.6 mA cm-2 to 1.5 mA cm-2