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 ai r to make hole transfer sites with p-Cu2O at 800 degreesC for 3 min. A tran sparent NiO layer was prepared on the surface of this device to make electr on transfer sites on the surface. This heat-treated device, having 2 mum Au layers, exhibited a remarkably stable steady photocurrent and a higher pho tocurrent quantum efficiency in a KI(10(-2) M) + I-2(10(-4) M) electrolyte solution when a thin transparent 0.05 mum NiO layer was deposited on the su rface to screen the electrolyte. During the heating of the Au-deposited cop per plate at 800 degreesC for 3 min, initially an alloy of Cu and Au was pr oduced, then a thin homogeneous p-Cu2O film was formed on the alloy by oxid izing the migrated Cu atoms onto the upper surface of the alloy. Characteri stics of the samples observed by means of XRD measurements and SEM microgra phs, V-I characteristics, photocurrent action spectra, the variations of th e photocurrent quantum efficiency with the deposited thickness of NiO and A u layers, photodegradation and improved chemical stability of the p-Cu2O ph otocathode and H-2 evolution from water by the photocathode were investigat ed to explain the junction effects of the modified p-Cu2O 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.