Enhanced photocatalytic water oxidation efficiency with Ni(OH)₂ catalysts deposited on α-Fe₂O₃ via ALD.

Atomic layer deposition was used to deposit NiO onto thin-film α-Fe2O3 electrodes for photocatalytic water splitting. Photoelectrochemical conditioning of the deposited NiO converts it to Ni(OH)2, which results in a stable reduction of the photocurrent onset potential for water oxidation by ~300 mV and improves photocurrent density by two-fold at 1.23 V vs. RHE as compared to untreated α-Fe2O3. This enhanced performance is shown to be due to improved charge separation with the ion-permeable Ni(OH)2 catalyst film. These results not only demonstrate one of the most effective water oxidation catalysts when integrated with hematite, but help establish the operational principles that lead to the improved performance.