Significantly enhanced photocurrent density in NiCo2O4/a-C/Si photoanode for water splitting

Abstract Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. In this work, amorphous carbon films (a-C), NiCo2O4 (NCO) and NCO/a-C bilayer films as protective layers were prepared on the surface of silicon, respectively. By comparing these protective layers of Si photoanode, we find that the NCO film can effectively protect Si from corrosion. It can not only lower initial potential but also increase photocurrent density. The NCO films were found to have the best catalytic performance. The photocurrent density of the NCO (60 nm)/Si photoanode is 185.6 mA/cm2 and that of the NCO (60 nm)/a-C (14 nm)/Si photoanode reaches high to 586.4 mA/cm2 at a voltage of 6 V vs SCE. The carbon interlayer reduces the width of depletion region built with n-Si, which further improves the current density of the NCO/Si photoanode. The photocurrent density of the NCO/a-C/Si photoanode is more than three times higher than that of the NCO/Si photoanode. The NCO/a-C bilayer film is an ideal protective layer of Si photoanode for photochemical water decomposition.