The bismuth vanadate thin layers modified by cobalt hexacyanocobaltate as visible-light active photoanodes for photoelectrochemical water oxidation

Bismuth vanadate thin films deposited using the pulsed laser deposition technique were modified using cobalt hexacyanocobaltate (Cohcc). The 2-step method of Cohcc nanocubes preparation was applied: i) metallic cobalt deposition and ii) cobalt electrooxidation in Co(CN)63− containing electrolyte. The presence of CN stretching vibrations was confirmed by Raman spectroscopy. The energy band gap was equal to 2.5 eV and was estimated using UV–Vis spectroscopy. The presence of Cohcc did not clearly affect the absorbance ability of tested films. Electrodes were tested as photoanodes for water splitting. It was shown that electrocatalytical properties of Cohcc in the oxygen evolution reaction strongly affect the photocurrent generated during FTO/BiVO4/Cohcc illumination. A significant, almost 1 V, shift of the onset potential towards lower potential was achieved. The role of Cohcc has been discussed on the basis of electrochemical and photoelectrochemical measurements. [Display omitted] •The two-step method of Cohcc nanocubes deposition on BiVO4 was developed.•Cohcc deposited on BiVO4 exhibits catalytic activity in the oxygen evolution reaction.•BiVO4/Cohcc has an almost 1 V lower onset potential of photocurrent generation.•The presence of Cohcc positively affects charge extraction efficiency.•A lower RCT of the electrode/electrolyte interface was achieved for modified electrodes.