Improvement of Photoelectrochemical Properties of CuO Photoelectrode by Li Doping

Abstract

We fabricated a Li doped CuO photoelectrode by doping CuO with Li to improve the photoelectrochemical properties of the CuO photoelectrode. The fabricated Li doped CuO photoelectrode was optimized by experimentally investigating Li doping concentration, annealing temperature, and spin coating deposition cycle. It was confirmed that Li doped CuO had increased light absorption, decreased energy band gap, and improved crystallinity. The Li-doped CuO photoelectrode had a porous surface, unlike the bare CuO photoelectrode, and had a low charge transfer resistance as well as a high flat band potential. The Li doping concentration experiment demonstrated that the 2 at% Li doped CuO photoelectrode had a superior photocurrent density value compared with a bare CuO photoelectrode. In the annealing temperature optimization experiment with a 2 at% Li doped CuO photoelectrode, it was found to have the best photocurrent density value at 500 oC. In experiments with various spin coating deposition cycles of the Li-doped CuO photoelectrode, the light absorption, energy bandgap, crystallinity, and electrical properties were affected by changes in the film thickness of the photoelectrode. In particular, we confirmed that a sample deposited with 4 spin coating cycles had the lowest interfacial resistance between the photoelectrode and the electrolyte, and the highest flat-band potential value. Consequently, we were able to obtain an improved photocurrent density of -1.68 mA/cm² compared to the bare CuO photoelectrode using the Li-doped CuO photoelectrode under the optimized conditions of Li 2 at%, an annealing temperature of 500 oC, and 4 cycles of spin coating depositions.