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