Two-step electrodeposition to fabricate the p–n heterojunction of a Cu2O/BiVO4 photoanode for the enhancement of photoelectrochemical water splitting

Abstract

A Cu₂O/BiVO₄ p–n heterojunction based photoanode in photoelectrochemical (PEC) water splitting is fabricated by a two-step electrodeposition method on an FTO substrate followed by annealing treatment. The structures and properties of the samples are characterized by XRD, FESEM, HRTEM, XPS and UV-visible spectra. The photoelectrochemical activity of the photoanode in water oxidation has been investigated and measured in a three electrode quartz cell system; the obtained maximum photocurrent density of 1.72 mA cm⁻² at 1.23 V vs. RHE is 4.5 times higher than that of pristine BiVO₄ thin films (∼0.38 mA cm⁻²). The heterojunction based photoanode also exhibits a tremendous cathodic shift of the onset potential (∼420 mV) and enhancement in the IPCE value by more than 4-fold. The enhanced photoelectrochemical properties of the Cu₂O/BiVO₄ photoelectrode are attributed to the efficient separation of the photoexcited electron–hole pairs caused by the inner electronic field (IEF) of the p–n heterojunction.