Deep surface reconstruction of Co-based cocatalyst on Ti-doped α-Fe2O3 photoanode for highly efficient water oxidation

Transition metal-based cocatalysts play important roles in promoting the surface kinetics of hematite (α-Fe2O3) photoanode. However, their performances are restricted by the shallow reconstruction process for generating highly efficient metal oxyhydroxides, where the oxygen evolution reaction (OER) occurs. Therefore, a Brnsted base-regulated strategy is developed to promote the in situ surface reconstruction of cocatalysts on Ti-doped α-Fe2O3 (Ti–Fe2O3) under photoelectrochemical conditions. After deep surface reconstruction by electrochemical activation, the CoWO4 cocatalyst decorated Ti–Fe2O3 photoanode (a-CoWO4/Ti–Fe2O3) delivers a photocurrent density of 0.88 mA cm−2 at 1.23 VRHE, which is about 3.0 times of activated Ti–Fe2O3 (a-Ti-Fe2O3) and 1.5 times of activated CoOx/Ti–Fe2O3. Tungstate promotes the surface reconstruction of cobalt-based cocatalyst, resulting in a significant increase in bulk charge separation efficiency (ηsep) and surface charge injection efficiency (ηinj). Moreover, the type-II heterojunction between CoWO4-derived CoOOH and a-Ti-Fe2O3 drives the rapid separation and transfer of photogenerated electron-hole pairs, and enhances the performance of Ti–Fe2O3 photoanode.