Some characteristics of Cu/Cu₂O/CuO nanostructure heterojunctions and their applications in hydrogen generation from seawater: effect of surface roughening

Abstract

Cu/Cu2O/CuO heterojunction were synthesized, using thermal oxidation under the flow of argon and oxygen gas mixture, as efficient photoelectrode for hydrogen generation. The Cu/Cu2O/CuO heterojunction were synthesized using un-roughed and roughed Cu foils. The resulting heterojunction samples were characterized using various techniques. The evaluated oxide layer (Cu2O/CuO) thicknesses for un-roughed and roughed samples are 4.2 and 8.5 m, respectively. XRD revealed that the oxide layer is a mix cubic Cu2O and monoclinic CuO crystalline phases with higher CuO ratio in the roughed sample. The surface morphology of the un-roughed sample is a porous surface that consisting of nanoflakes whereas surface morphology of the roughed sample is randomly oriented nanowires. The Cu/Cu2O/CuO nanostructured surface is superhydrophilic, with water contact angles of 11.12 and 0° for un-roughed and roughed samples, respectively. The roughed sample has higher absorbance over the entire studied wavelength range. The obtained values of the optical band gap for un-roughed and roughed samples are 2.48 and 2.39 eV, respectively. The photocurrent density of the roughed photoelectrode is much greater than that of un-roughed photoelectrode. The roughed photoelectrode has a photocurrent density of – 0.151 mA/cm2 at – 0.85 V and a photoconversion efficiency of 0.55 % when illuminating with 340 nm light. This work offers a promised Cu/Cu2O/CuO photoelectrode for hydrogen generation from seawater.

Cu2O/CuO composite for efficient performance in photoelectrochemical and optoelectronics applications

“…Among them, Cu 2 O has garnered great attention for PEC applications due to its favorable optical and electronic properties which can function as a photocathode that enables the effective utilization of solar photons [16][17][18][19][20] such as a direct band gap of about 2.1 eV and a high absorption coefficient [21][22][23]. It is appropriate for absorbing a huge percentage of the solar spectrum with a greatest solar conversion efficiency of 18.1% and a resultant theoretical photocurrent of 14.7 mA cm −2 based on the AM 1.5 spectrum [24].…”