Effects of annealing temperature on GO–Cu2O composite films grown by electrochemical deposition for PEC photoelectrode

•GO–Cu2O composite films were grown by electrochemical deposition method.•Effects of annealing temperature on GO–Cu2O composite films were investigated.•The highest photocurrent density, −4.75 mA/cm2, was obtained from 200 °C sample.•The co-existence of Cu2O and Cu phases by reduction decreased photocurrent density.

In this work, graphene oxide–cuprous oxide (GO–Cu2O) composite films were grown on fluorine-doped tin oxide substrates by electrochemical deposition. We investigated the effects of the annealing temperature on the morphological, structural, optical and photoelectrochemical (PEC) properties of GO–Cu2O composite films. As a result, our work shows that while GO–Cu2O composite films exhibit the highest XRD (111) peak intensity at 300 °C sample, the highest photocurrent density value obtained was −4.75 mA/cm2 at 200 °C sample (using 0.17 V versus a reversible hydrogen electrode (RHE)). In addition, a reduction reaction at 300 °C sample was observed using XPS analysis from the shift in the O1s peak in addition to a weaker O1s peak intensity.