Visualizing Overall Water Splitting on Single Microcrystals of Phosphorus-Doped BiVO₄ by Photo-SECM

Area of Science:

• Materials Science
• Electrochemistry
• Photocatalysis

Background:

• Bismuth vanadate (BiVO₄) is a promising photocatalyst for water oxidation.
• Achieving overall water splitting (OWS) with BiVO₄ is challenging due to its positive conduction band edge, limiting efficient hydrogen evolution.

Purpose of the Study:

• To visualize and quantitatively measure overall water splitting (OWS) at the single-particle level.
• To investigate the spatial distribution of oxygen and hydrogen evolution on phosphorus-doped BiVO₄ microcrystals.

Main Methods:

• Utilized photoscanning electrochemical microscopy (photo-SECM) with a chemically modified nanotip.
• The nanotip acted as both a light guide for illumination and an electrochemical nanoprobe for measuring local fluxes.
• Examined a single truncated bipyramidal microcrystal of phosphorus-doped BiVO₄.

Main Results:

• Successfully visualized OWS at a single BiVO₄ microcrystal for the first time.
• Observed distinct current patterns for O₂ and H₂ fluxes, correlating with electron and hole accumulation on specific crystal facets ({010} and {110}).

Conclusions:

• The developed photo-SECM approach enables nanoelectrochemical mapping of photocatalyst activity at the subfacet level.
• Provides crucial insights into the surface-dependent activity of BiVO₄ for water splitting.