Orientation-Engineered Epitaxial BiVO4 Thin Films for Efficient Photoelectrochemical Glycerol Valorization

Abstract

Crystallographic orientation-engineered epitaxial BiVO4 thin film photoanodes were fabricated to systematically investigate the influence of crystallographic anisotropy on photoelectrochemical (PEC) glycerol oxidation. To decouple orientation-driven effects, c-axis-oriented BiVO4 (00l) and b-axis-oriented BiVO4 (0k0) films were prepared as single- orientation epitaxial layers and evaluated under identical AM 1.5 G solar illumination conditions. The b-axis oriented BiVO4 (0k0) film exhibited approximately 2.4 times higher photocurrent density and a 2.6-fold enhancement in charge separation efficiency compared to the c-axis oriented BiVO4 (00l) film, achieving a maximum production rate of 81.4 mmol m-2·h-1. Further photoelectrochemical characterization and charge-transport analyses indicate that the enhanced performance of the (0k0)-oriented BiVO4 primarily originates from improved bulk charge separation and charge transport rather than differences in surface catalytic activity. These results demonstrate that crystallographic orientation control is a key design parameter for developing energy-efficient oxide photoanodes for solar-driven glycerol oxidation beyond conventional water oxidation.