Highly Efficient Photoelectrochemical Water Splitting from Hierarchical WO₃/BiVO₄ Nanoporous Sphere Arrays

Nanoarchitecture of bismuth vanadate (BiVO₄) photoanodes for effectively increasing light harvesting efficiency and simultaneously achieving high charge separation efficiency is the key to approaching their theoretic performance of solar-driven water splitting. Here, we developed hierarchical BiVO₄ nanoporous sphere arrays, which are composed of small nanoparticles and sufficient voids for offering high capability of charge separation. Significantly, multiple light scattering in the sphere arrays and voids along with the large effective thickness of the BiVO₄ photoanode induce efficient light harvesting. In addition, attributed to ultrathin two-dimensional Bi₂WO₆ nanosheets as the precursor, the synergy of various enhancement strategies including WO₃/BiVO₄ nanojunction formation, W-doping, and oxygen vacancy creation can be directly incorporated into such a unique hierarchical architecture during the one-step synthesis of BiVO₄ without complex pre- or post-treatment. The as-obtained photoanode exhibits a water splitting photocurrent of 5.5 mA cm^–2 at 1.23 V versus RHE under 1-sun illumination, among the best values reported up-to-date in the field.