Atomic Layer Deposition of a Submonolayer Catalyst for the Enhanced Photoelectrochemical Performance of Water Oxidation with Hematite

Abstract

Hematite photoanodes were coated with an ultrathin cobalt oxide layer by atomic layer deposition (ALD). The optimal coating1 ALD cycle, which amounts to <1 monolayer of Co(OH)₂/Co₃O₄resulted in significantly enhanced photoelectrochemical water oxidation performance. A stable, 100–200 mV cathodic shift in the photocurrent onset potential was observed that is correlated to an order of magnitude reduction in the resistance to charge transfer at the Fe₂O₃/H₂O interface. Furthermore, the optical transparency of the ultrathin Co(OH)₂/Co₃O₄ coating establishes it as a particularly advantageous treatment for nanostructured water oxidation photoanodes. The photocurrent of catalyst-coated nanostructured inverse opal scaffold hematite photoanodes reached 0.81 and 2.1 mA/cm² at 1.23 and 1.53 V, respectively.