Co ₃O ₄-decorated hematite nanorods as an effective photoanode for solar water oxidation

In this Article, we report a strategy to perform in situ incorporation of oxygen evolution catalyst, Co ₃O ₄, during hydrothermal growth of Fe ₂O ₃ nanorod arrays. It was found that the highest photocurrent increase and onset potential shift was observed with 5% Co ²⁺. The photocurrent density increases from 0.72 for the pristine Fe ₂O ₃ nanorod to 1.20 mA/cm ² at 1.23 V versus RHE (i.e., 67% improvement) with 5% Co ²⁺ added. Concomitant with this improvement was a shift in the onset potential by ∼40 mV and improvements in incident-photon-to-current efficiencies and oxygen evolution. Hematite photoanodes with in situ deposition of Co ₃O ₄ nanoparticles showed better performance than those prepared by ex situ procedures because of high surface roughness, larger Co ₃O ₄/hematite interfacial area, and smaller Co ₃O ₄ particle size.