The conversion of water to oxygen and hydrogen, or water splitting, is crucial to the solar hydrogen economy and solar driven carbon dioxide reduction for fuel-producing reactions. Water oxidation is a thermodynamically uphill and kinetically hindered reaction. Reducing the high activation energy to facilitate the splitting of water can be done through the development of efficient, stable water oxidation catalysts. One particular metal oxide system of interest is birnessite, a naturally occurring layered manganese oxide with interstitial layers of water and alkali metal cationic species. In this report, a synthetic strategy to enhance the electrocatalytic activity of birnessite for the oxygen evolution reaction (OER) by simultaneous doping and intercalation of Co<sup>3+</sup> and Fe<sup>2+</sup> redox active metals, respectively, is reported. Electrocatalytic studies showed that the increasing activity of birnessite species is in the following order: standard potassium birnessite, cobalt-doped potassium birnessite, iron-intercalated birnessite, iron-intercalated birnessite with cobalt dopant. Synthesized samples were characterized by X-ray diffractometry, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-optical emission spectrometry, X-ray photoelectron spectroscopy, and cyclic voltammetry. Experimental data suggest a synergistic effect between doping and intercalation of metal ion species within the manganese oxide lattice and interstitial cationic regions, improving the water oxidation activity of birnessite beyond an individual doping or intercalation procedure.

Layered, ternary water oxidation catalyst prepared by in-layer cobalt doping, and interlayer iron-oxo cluster intercalation in Mn-O-based birnessite

255th National Meeting (2018)

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