Controlled nanostructured morphology of BiVO₄ photoanodes for efficient on-demand catalysis in solar water-splitting and sustainable water-treatment

Improving the kinetic properties of Bismuth vanadate (BiVO₄) by nanoparticles or controlling the morphology of decagonal particles with crystal facets is receiving strong interest. Accordingly, we report an effective water-splitting and -purification system based on the photocatalytic performance of BiVO₄ using a combined nano-structured morphology and crystal facets. BiVO₄ thin film spin-coated at different Bi/V concentrations (viz. 1, 2, and 3) revealed a drastic change from nanoparticle (multifacet) to combined nanostructured morphology i.e., nanoparticles and sheet-like (decagonal facet). Such a morphology with multi-crystal facet in which {0 1 0} and {1 1 0} planes are prevalently active surfaces for Bi/V = 3 sample was found to disrupt the laminar boundary layer effectively, as confirmed from the lower contact-angle. Moreover, improved intercalation of the electrolyte in the nanoporous BiVO₄ layer resulted in excellent photoelectrochemical performance with a photocurrent density of 1.98 mA/cm² (@1.23 V_RHE) and on-set potential of 0.40 V_RHE in hole-scavenger compared to simple morphology. Congo-red (CR) and methylene-blue (MB) dye remediation under solar-radiation indicated an excellent degradation efficiency of 86 % in 90 min and 96 % in 300 min, respectively. Interestingly, the dual nanostructured morphology maintained consistent performance in ~5 (CR) and 9 (MB) repeated batch runs, demonstrating their high photocatalytic activity under visible-light and good durability in repeated use. Our results suggest that changes in the Bi/V ratio help tailoring the crystal facet from the {0 1 0} to a combined {0 1 0} and {1 1 0} with the evolution of dual nanostructured morphology, which increases the charge-transfer efficiency and is beneficial for efficient water-splitting and water-treatment processes.