Enabling high low-bias performance of Fe2O3 photoanode for photoelectrochemical water splitting

Fe2O3 is a promising photoanode material used for photoelectrochemical water splitting due to its narrow bandgap and excellent stability in solution. However, because the nanorods shrink and coalesce when annealed under high temperatures, the charge separation and injection efficiencies are suppressed in the conventional nanocoral Fe2O3, resulting in its high bias potential and low photocurrent density. Herein, by improving the radial growth of FeOOH precursor, highly dispersed Fe2O3 nanorods could be prepared. It enabled them to have sufficient light-harvesting and short charge transport distance, high light absorption and charge separation/injection efficiencies, increased photocurrent density and reduced onset potential Von. The optimized Fe2O3 photoanodes obtained a remarkable low-bias photocurrent density of 0.84 mA cm-2 at 1.0 V versus reversible hydrogen electrode (vs. RHE). It was further improved to 1.36 mA cm-2 at 1.0 V vs. RHE with the Von reduced to 0.50 V vs. RHE when post-treated with a solvothermal method and loaded with NiOOH/FeOOH cocatalysts. The applied bias photo-to-current conversion efficiency was maximized to 0.45% at 0.84 V vs. RHE.