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.
Highlights
An essential issue for the sustainable development of human society is the construction of a social energy system based on renewable energies such as solar, wind, and geothermal
To determine the potential of the valence band maximum (VBM), spetroscopy in air (PESA) measurement was conducted, and VBM potential of Zinc telluride (ZnTe) prepared by close spaced sublimation (CSS) on ITO coated glass plate was found to be 5.3 eV, 0.9 V vs standard hydrogen electrode (SHE), as shown in Fig. S2 of the supplementary material
Enhancement of the cathodic photocurrent was attributed to the increased gain size and improved crystallinity owing to the higher substrate temperature of 450 ○C during the second step
Summary
An essential issue for the sustainable development of human society is the construction of a social energy system based on renewable energies such as solar, wind, and geothermal. It should be noted that 0 VRHE is equal to the hydrogen evolution potential and the photocurrent at >0 VRHE can contribute to energy conversion.. The ZnTe-based photocathode surface modified with Pt and CdS showed a clear cathodic photoresponse, which contributes to the hydrogen evolution from water in an aqueous phosphate buffer solution. The modified ZnTe-based photocathode showed a cathodic photocurrent of 1.5 mA cm−2 at 0 VRHE under simulated sunlight of AM 1.5G and incident-photon-to-current conversion efficiencies (IPCEs) higher than 30% at 420–520 nm, reaching 40% IPCE at 460 nm under an applied potential of 0 VRHE.. The photocathode showed non-zero IPCEs at
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