Heterojunction Cr2O3/CuO:Ni photocathodes for enhanced photoelectrochemical performance

Heterojunction p-type photoelectrodes consisting of chromium oxide (Cr2O3) and copper oxide (CuO)-doped nickel (Ni) were prepared using aerosol-assisted chemical vapour deposition (AACVD) and spin-coating. All samples were photoresponsive and showed a photocathodic current in 0.5 M Na2SO4 under simulated solar illumination. The photocathode with an optimal composition of 3 layers of CuO and 0.5% Ni showed an enhanced photoactivity relative to bare Cr2O3. Based on the optical characterization and the flatband potential calculation, the fabricated Cr2O3, Cr2O3/CuO and Cr2O3/CuO:Ni can absorb visible light, which enables the water reduction reaction. Moreover, electrochemical impedance spectroscopy revealed that the charge transfer resistance of Cr2O3/CuO:Ni was decreased. Thus, in the heterojunction structure, the photogenerated electrons in Cr2O3 were transferred to the CuO:Ni layer, which then contributes to a high photoactivity. The combined advantages of the two strategies (heterojunction and doping) provide favourable charge transport characteristics of the materials.