Active MnOx Electrocatalysts Prepared by Atomic Layer Deposition for the Oxygen Evolution and Oxygen Reduction Reactions, Katie L. Pickrahn,Sang Wook Park, Yelena Gorlin, Han-Bo-Ram Lee, Thomas F. Jaramillo, and Stacey F. Bent, Advanced Energy Materials, 2012
http://dx.doi.org/10.1002/aenm.201200230
Abstract
The ability to deposit conformal catalytic thin fi lms enables opportuni- ties to achieve complex nanostructured designs for catalysis. Atomic layer deposition (ALD) is capable of creating conformal thin fi lms over complex substrates. Here, ALD-MnO x on glassy carbon is investigated as a catalyst for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), two reactions that are of growing interest due to their many applica- tions in alternative energy technologies. The fi lms are characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, ellipsometry, and cyclic voltammetry. The as-deposited fi lms consist of Mn(II) O, which is shown to be a poor catalyst for the ORR, but highly active for the OER. By controllably annealing the samples, Mn 2 O 3 catalysts with good activity for both the ORR and OER are synthesized. Hypotheses are presented to explain the large difference in the activity between the MnO and Mn 2 O 3 catalysts for the ORR, but similar activity for the OER, including the effects of surface oxidation under experimental conditions. These catalysts synthesized though ALD compare favorably to the best MnO x catalysts in the literature, demonstrating a viable way to produce highly active, conformal thin fi lms from earth-abundant materials for the ORR and the OER.
