(560cx) Multifunctional Vanadium-Doped Cobalt Oxide Layer on Silicon Photoanodes for Efficient Photoelectrochemical Water Oxidation

Due to the limited availability of fossil fuels, there is an urgent demand to develop sustainable energy technologies for efficient utilization of renewable energy sources, particularly solar energy. Photoelectrochemical (PEC) water splitting has emerged as an attractive strategy to convert and store solar energy into hydrogen fuel. However, developing highly efficient photoanodes for PEC cells to meet industrial requirements remains a challenge. Silicon has high carrier mobilities and mature technologies for fabrication and modification, which is regarded as a promising material for PEC electrodes. Here, we present a study of effectively engineering the onset potential of Si photoanodes through doping of V into Co oxide film by a low-cost way of magnetron co-sputtering deposition on p⁺n junction Si cell (p⁺nSi/CoVO). Using such a p⁺nSi/CoVO photoanode, a high photocurrent density of 29.15 mA cm^-2 (at 1.23 V vs the reversible hydrogen electrode) as well as a high photovoltage of 608 mV are achieved. Moreover, a successful decrease of the onset potential by 40 mV to 1 V (at 1 mA cm^-2) and a 3.6-fold increase in incident photons to current conversion efficiency (IPCE) are reached, compared to those of p⁺nSi/CoO without V-doping. We found that the doped V atoms can decrease the charge transfer resistance of Co₃O₄ film, serve as Lewis acid to increase local pH value, and facilitate the generation of Co(IV) oxo-bridged species to lower the kinetic barrier of oxygen evolution reaction (OER), thus to decrease the onset potential of p⁺nSi/CoVO in OER. This work suggests a general approach to improve the performance of OER catalysts by engineering active sites and local chemical environment through element doping.

References:

[1] Xing, Z.; Wu, H.; Wu, L.; Wang, X.; Zhong, H.; Li, F.; Shi, J.; Song, D.; Xiao, W.; Jiang, C.; Ren, F. A multifunctional vanadium-doped cobalt oxide layer on silicon photoanodes for efficient and stable photoelectrochemical water oxidation. J. Mater. Chem. A 2018, 6, 21167-21177.