Preparation Of Oxide Semiconductor Photoelectrodes And Their Properties After Co-Pi Surface Modification

Hydrogen has the potential to meet the requirements as a clean fuel in future if it can be produced using the most abundant energy source in the world, the sun. Water splitting with sunlight has been envisioned as a promising way to converse solar energy and store it in chemical bonds. Photoelectrochemical cellswith semiconductor photoelectrodes have been widely studied since its first demonstration. However, the photoelectrochemical water splitting has been limited within labs forits efficiency and intractable practical obstacles. In this thesis, we will focus on removing those obstacles of semiconductor photoelectrode while improving the quantum efficiency with the help of Co-Pi as a surface catalyst.The effect of Co source on the electrochemical water oxidation of Co-Pi catalyst was investigated. The studies indicate that the sample electrodeposited from Co(NO3)2 precursor has better activity than that from COSO4. The stability of Co-Pi catalyst in different electrolyte was also studied. The results shows that Co-Pi catalyst is stable in most electrolyte, especially at high pH value.Then, Co-Pi catalyst is introducedinto photoelctrochemcial cells in which an n-type semiconductor acts as a work electrode. We have prepared highly efficient Mo-doped BiVO4 photoanode using a simple spin-coating method. And after Co-Pi modification, the IPCE of this photoanode is relatively high. The efficiency at 1V vs RHE from 450to 470nm are the highest among the semiconductor photoanodes that have been reported. This work demonstrates that Co-Pi catalyst can significantly enhance the photoelectrochemical performance of Mo-doped BiVO4 photoanode. This improvement comes from the efficient utilization of holes at the surface of the photoanode at low bias.WO3 photoanode was prepared with a straightforward electrodeposition method. The WO3 thin film was about 1μm in thickness. The photoelectrochemical activity of WO3 thin films was investigated. Photocurrent density of the WO3 photoanode can reach as high as 2.9 mA/cm2(1V vs Ag/AgCl under 500W xenon lamp illumination). The highest quantum efficiency for the WO3 photoanode in 1M HClO4 solution is 25% (1V vs Ag/AgCl,400nm), four times higher than the former report with the same method. We also modified the as-prepared photoanode by Co-Pi oxygen-evolving catalyst, and the photocurrent over the whole potential range was enhanced.