Porous Cupric Oxide: Efficient Photocathode for Photoelectrochemical Water Splitting

Abstract Photoelectrochemical (PEC) water splitting is considered as an effective approach to generate hydrogen at the cathode, and can be used as a means to generate green energy. A simple electrochemical deposition technique is developed for the synthesis of CuO nanostructures. CuO with different morphologies like porous 2D sheets, porous bipyramids, particles, and spheres are developed after oxidation of the electrodeposited Cu nanostructure. Among them, CuO porous 2D nanosheets show the best activity as photocathode towards PEC water splitting due to the high light absorbance and high electrochemically active surface area (ECSA). CuO porous 2D sheets contains three times higher ECSA compared to CuO particles, indicating their higher electrochemical activity. CuO porous 2D sheets can generate a current density of 3.09 mA cm −2 at an applied potential of −0.1 V vs RHE in 0.5 M Na 2 SO 4 solution. Furthermore, Mott‐Schottky measurements demonstrate that CuO porous 2D sheets possess high carrier density, 8.18×10 20 cm −3 , and a high flat band potential of 1.215 V vs. RHE. Thus, CuO porous 2D sheets have excellent conductivity and a high degree of band bending. After PEC water splitting, XRD analysis was carried out to reconfirm the photostability of the CuO porous 2D sheets. It may be due to the higher charge transportation in the porous structures.