Relationship between the morphology for the photo-electrode of copper bismuth oxide and the photo-electrochemical activity related to water reduction

Abstract

The relationship between the morphology of the photo-electrode of copper bismuth oxide (CuBi2O4) and the activity to generate cathodic photo-current in a deoxygenated aqueous electrolyte was investigated. The electrodes were fabricated by the electrodeposition of the precursor on a conductive substrate following heat treatment. As a simple comparison, a randomly porous electrode was compared with a dense electrode. A dense electrode and a porous electrode were fabricated by selecting the potential to deposit the precursor; formation of the electrode was confirmed by measuring X-ray diffraction patterns and scanning electron microscope images. The values of the absorbed photon to current efficiency were calculated by measuring steady photocurrents in a deoxygenated electrolyte at a constant potential under irradiation of monochromatic visible lights. The dense electrode shows larger values than the porous electrode. To consider the difference in the values between the electrodes, the values were also calculated for the current generated in the electrolyte of dissolved oxygen to scavenge electrons. Eventually, it is considered that for CuBi2O4 electrodes, dense morphologies are more suitable than porous morphologies to produce hydrogen by photo-electrochemical water reduction in terms of charge separation inside the electrode. Dense and porous photo-electrodes of copper bismuth oxide were fabricated by selecting the potential to deposit the precursor and following heat treatment. The former is more efficient to generate the current for water photo-reduction in a deoxygenated aqueous electrolyte due to more facile transfer of electrons inside the electrode.