A Robust and Photocatalytic Cr2O3@CuO Photocathode for Photoelectrochemical Hydrogen Production

The study represents the synthesis of photoelectrodes Cr2O3@CuO with hydrothermal and electrochemical deposition (various chronoamperometric deposition of CuO 15, 30 and 45 minutes) for photocathode heterostructure for photoelectrochemical hydrogen production. Cr2O3 is more resistant to photocorrosion but performs at a lower photocatalytic performance. Although CuO absorbs in the visible region, it nevertheless enables photocorrosion under mild conditions. According to these advantages of electrodes, Cr₂O₃@CuO photocathode is designed, and Cr₂O₃ photocurrent density increased 9 times to -0.911 mA cm-2 (-0.5 V vs. Ag/AgCl) for chronoamperometric deposition of 45 minutes of CuO (S30) under 100 mW cm-2 solar irradiance. The surface morphology of Cr2O3@CuO photocathode consists of Cr₂O₃ nanosphere and CuO layer, confirmed by scanning electron microscopy. To investigate photostability and catalytic activity on Hydrogen Evolution Reaction (HER) under solar light, electrochemical impedance spectroscopy (EIS) and chronoamperometric measurement are conducted, indicating polarisation resistance (Rp) is dramatically decreased with combined Cr2O3@CuO heterostructure compared to pristine Cr₂O₃ electrode, and Cr2O3@CuO photocathode performs the most photostability performance (-0.5 V vs. Ag/AgCl) under solar irradiation for 3 hours. Mott-Schottky measurement indicates that Cr2O3 and CuO act as p-type semiconductors, and Cr2O3@CuO heterostructure conductive band (CB) shifts to a more negative energy level of H+/H2 consequently hindering photocorrosion of CuO into the electrochemical double layer.