Porous TaON Photoanodes Loaded with Cobalt-Based Cocatalysts for Efficient and Stable Water Oxidation Under Visible Light

Abstract

Porous photoanodes for visible-light-induced water oxidation were prepared via simple electrophoretic deposition of TaON particles, preliminarily modified with CoO x nanoparticles, on a Ti substrate. Post-necking process involving methanolic TaCl5 solution and subsequent heating in NH3 stream formed bridges between TaON particles, which facilitated electron transport within the porous electrode and thereby increased the photocurrent significantly. The temperature of the NH3 treatment in the post-necking process significantly influenced both the charge transport through the bridges and the activity of the CoO x cocatalyst for water oxidation, thus producing maximum photocurrent after heating at 723 K. The highly dispersed CoO x nanoparticles considerably improved the stability of the photocurrent due to efficient capture of photogenerated holes and consequent reduction of the probability of self-oxidative deactivation of the TaON surface. The combination of phosphate buffer solutions with a highly dispersed CoO x cocatalyst on the TaON surface significantly increased the photocurrent due to the in situ photoelectrochemical production of an amorphous cobalt/phosphate (Co–Pi) phase, which covers the TaON surface almost entirely, and consequently improved the its stability in long-term photoirradiation.