Coexposed TiO₂’s (001) and (101) facets in TiO₂/BiVO₄ photoanodes for an enhanced photocatalytic fuel cell

This paper reports an investigation on the role of coexposed TiO₂’s (001) and (101) facets on the performance of TiO₂/BiVO₄ photoanodes in the photocatalytic fuel cell. Here, the exposure of these facets was obtained by synthesizing TiO₂ with different morphologies, i.e. nanospindles, nanocube, nanooctahedra and nano-truncated octahedra. Based on the result, coexposed (001) and (101) facets were found to be responsible for the enhancement of photoelectrochemical response. The highest photocurrent density was achieved when the photoanode was fabricated using TiO₂ nano-truncated octahedra/BiVO₄ (29.8 μA/cm² at 0.8 V vs. NHE), which was primarily due to the improvement of charge separation as a result of the synergistic effect between the formation of type-II heterojunction of TiO₂/BiVO₄ and internal surface heterojunction of (001) and (101) facet. A similar trend was also observed in the PFC system when RhB was used as fuel. Under the illumination of 13 W LED light, the highest electric power (0.00232 mW/cm²) was obtained with TiO₂ nano-truncated octahedra/BiVO₄ photoanode. However, TiO₂ nanospindles/BiVO₄ was found to be more effective in removing RhB due to its high surface area. Such variation was believed due to the fact that TiO₂ nanospindles had less exposure of (001) facet than TiO₂ nano-truncated octahedra.