Sunlight Selective Photodeposition of CoOx(OH)y and NiOx(OH)y on Truncated Bipyramidal BiVO4 for Highly Efficient Photocatalysis

Facet-engineered monoclinic scheelite BiVO₄ particles decorated with various cocatalysts were successfully synthesized by selective sunlight photodeposition of metal or metal oxy(hydroxide) nanoparticles onto the facets of truncated bipyramidal BiVO₄ monoclinic crystals coexposing {010} and {110} facets. X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning Auger microscopy revealed that metallic silver (Ag) and cobalt (oxy)hydroxide (CoO_x(OH)_y) particles were selectively deposited onto the {010} and {110} facets, respectively, regardless of the cocatalyst amount. By contrast, the nickel (oxy)hydroxide (NiO_x(OH)_y) photodeposition depends on the nickel precursor amount with an unprecedented selectivity for 0.1 wt % NiO_x(OH)_y/BiVO₄ with a preferential deposition onto the {010} facets and the edges between the {110} facets. Moreover, these noble metal-free heterostructures led to remarkable photocatalytic properties for rhodamine B photodecomposition and sacrificial water oxidation reactions. For instance, 0.2 wt % CoO_x(OH)_y/BiVO₄ led to one of the highest oxygen evolution rates, i.e., 1538 μmol h^-1 g^-1, ever described which is ten times higher than that found for bare BiVO₄. The selective deposition of cobalt (oxy)hydroxide species onto the more electron-deficient facet of truncated bipyramidal monoclinic BiVO₄ particles favors photogenerated charge carrier separation and therefore plays a key role for efficient photochemical oxygen evolution.