Improving oxygen evolution efficiency in BiVO4 photoanodes through surface facet control with TiCl3 as a structure guide agent

Efficient conversion of solar energy into chemical fuels through photoelectrochemical (PEC) water oxidation replies on highly efficient photoanodes. The surface crystal facet of photoanode plays a critical role in determining the injection efficiency of photocarriers from photoanode to electrolyte. Thus, controlling the formation of surface crystal facets is believed to be an effective strategy for improving the energy conversion efficiency of photoelectrodes. However, it is still challenging to technically control the formation of surface crystal facets. Herein, we proposed to use TiCl3 as structure guide agent in hydrothermally synthesizing BiVO4 photoanodes. By adjusting the amount of structure-directing agent and the temperature of the precursor, we obtained a series of BiVO4 photoanodes with different amount ratios of {010} and {110} facets. It was found that a photocurrent density of 1.07 mA/cm2 could be obtained when the {010} facet was grown perpendicular to the substrate at 75% area ratio, which is much higher than the 0.20 mA/cm2 of the randomly oriented sample of the crystal. The incorporation of structure-directing agents reduces the surface energy of the corresponding crystalline surfaces, leading to an increase in charge separation capacity attributed to the different charge transfer distances in various crystal orientations. This work provides new proposals into the rational design of photoanode crystal surface structures for efficient PEC water oxidation, may have significant implications for the development of highly efficient photoanodes in the future.