The oxygen evolution reaction (OER), in which water is oxidized to molecular oxygen, is an important part of many technologies including the photoelectrochemical splitting of water. There is much interest in the development of earth-abundant, affordable electrocatalysts for OER. In this talk, we describe the use of atomic layer deposition (ALD) to deposit nanometer thick electrocatalyst layers of transition metal oxides for OER. ALD is a vapor phase deposition technique capable of forming highly uniform conformal thin films with a fine control over film thickness and film composition. It is becoming an attractive method for synthesizing catalytic thin films, opening new avenues for advanced catalytic designs. We synthesize MnOx- and NiO-based catalysts using ALD and test them in the oxygen evolution reaction. The catalysts are characterized using a variety of techniques and their activity is measured by cyclic voltammetry. The ALD process produces Mn(II)O, which can be changed to higher oxidation states by annealing. Annealing the film to form Mn2O3 generates a catalyst that is active for OER, approaching the activity of the most active MnOx catalysts known. Because ALD provides excellent control over film thickness, we show that the activity of the MnOx depends on the film thickness at the nanoscale. This effect is explored using other metal oxide films for comparison, and the results indicate that beyond a critical thickness, charge transport limitations begin to reduce the activity of the films. We also apply ALD to achieve compositional control over ternary metal oxide and doped transition metal oxide thin films. We discuss further implications of electrocatalyst design using ALD, including applications to photoelectrochemical water splitting.

Atomic layer deposited transition metal oxides as active electrocatalysts for the oxygen evolution reaction

251st National Meeting (2016)

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