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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