Junction effects of p-Cu2O photocathode with layers of hole transfer sites (Au) and electron transfer sites (NiO) at the electrolyte interface

A well cleaned copper plate with a thin Au layer deposited was heated in air to make hole transfer sites with p-Cu 2 O at 800 °C for 3 min. A transparent NiO layer was prepared on the surface of this device to make electron transfer sites on the surface. This heat-treated device, having 2 µm Au layers, exhibited a remarkably stable steady photocurrent and a higher photocurrent quantum efficiency in a KI(10 -2 M) + I 2 (10 -4 M) electrolyte solution when a thin transparent 0.05 µm NiO layer was deposited on the surface to screen the electrolyte. During the heating of the Au-deposited copper plate at 800 °C for 3 min, initially an alloy of Cu and Au was produced, then a thin homogeneous p-Cu 2 O film was formed on the alloy by oxidizing the migrated Cu atoms onto the upper surface of the alloy. Characteristics of the samples observed by means of XRD measurements and SEM micrographs, V - I characteristics, photocurrent action spectra, the variations of the photocurrent quantum efficiency with the deposited thickness of NiO and Au layers, photodegradation and improved chemical stability of the p-Cu 2 O photocathode and H 2 evolution from water by the photocathode were investigated to explain the junction effects of the modified p-Cu 2 O with the Cu + Au alloy and NiO transparent film at the electrolyte interface. Here, the NiO layer and Au particles in the Au + Cu alloy efficiently act as the electron-transfer and hole-transfer sites, respectively.