Thermal conversion synthesis of Cu2O photocathode and the promoting effects of carbon coating

•Cu2O photocathode has been prepared by a thermal conversion method.•Carbon coating has been deposited on Cu2O using starch sol as carbon source.•Cu2O shows an enhanced photoelectrochemical performance with the carbon coating.

Simplifying the synthesis of cuprous oxide (Cu2O) photocathode has turned out to be critical for scalable application. Herein, we present a novel thermal conversion approach to synthesize a shell/core structured Cu2O/Cu photocathode. In this method a shell comprising a mixture of CuO and Cu2O is obtained by heating Cu mesh at 500 °C in air beforehand, and subsequent annealing in N2 atmosphere converts the unwanted CuO into Cu2O gradually, which results in the desired Cu2O/Cu structure. A slightly viscous starch sol coats the Cu2O shell as carbon source, after carbonizing under N2 atmosphere, the Cu2O/Cu is covered with compact carbon films, i.e. C/Cu2O/Cu. Photoelectrochemical experiments reveal that the introduction of carbon layers on Cu2O enhances the photocurrent density from − 1.5 to − 2.75 mA·cm− 2 at 0 V vs. reversible hydrogen electrode (RHE). Moreover, the deposition of carbon films on Cu2O in this work has little effect on improving the stability.

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