Plasmonic enhancement in BiVO₄ photonic crystals for efficient water splitting

Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H₂ conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO₄ photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm^-2 at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode.