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.