Screening of Electrocatalysts for Photoelectrochemical Water Oxidation on W-Doped BiVO4 Photocatalysts by Scanning Electrochemical Microscopy

Oxygen evolution reaction (OER) electrocatalyst arrays for photoelectrochemical (PEC) water oxidation were fabricated on a metal oxide semiconductor photoelectrode, W-doped BiVO4 (BiVW-O). The electrocatalysts (IrOx, Pt, Co3O4) were prepared on a drop cast film of BiVW-O on fluorine-doped tin oxide (FTO) with a picoliter solution dispenser or photodeposition with light irradiation through an optical fiber. The prepared arrays were tested for PEC water oxidation in 0.2 M sodium phosphate buffer (pH 6.8) using scanning electrochemical microscopy modified with an optical fiber. Pt and Co oxide electrocatalysts showed an enhanced photocurrent for PEC water oxidation, while the other metal oxide catalysts including IrOx, which is known as an excellent water oxidation electrocatalyst on a metal substrate, were not effective. These results were confirmed with bulk film studies. A cobalt phosphate (Co-Pi) electrocatalyst was also tested as a bulk film on BiVW-O and showed improvement for PEC water oxidation. Preliminary characterization (X-ray diffraction and X-ray photoelectron spectroscopy) was also performed for these catalysts. The results:indicate that considerations of the semiconductor photocatalyst/electrocatalyst interface are important in determining the effectiveness of materials for the photodriven OER.