The slow kinetics of the water oxidation half-reaction limit the efficiency of both electricity and photodriven water splitting technologies. We have studied a variety of electrocatalysts for the oxygen evolution reaction (OER) in a thin film geometry, enabling simple and direct comparison of the activity of different catalyst materials. Ni0.9Fe0.1Ox was found to be the most active water oxidation catalyst in basic media, passing 10 mA cm-2 at an overpotential of 336 mV with a Tafel slope of 30 mV dec-1 and intrinsic OER activity roughly an order of magnitude higher than IrOx control films and similar to or better than the best known OER catalysts in basic media. The high activity is attributed to the in situ formation of a layered Ni0.9Fe0.1OOH oxyhydroxide species with nearly every Ni atom electrochemically active.We will also discuss recent work to elucidate the role of Fe in enhancing the activity of NiOOH. Electrochemical, electrical, and surface spectroscopic characterizations of electrodeposited Ni and mixed Ni-Fe hydroxides are used to investigate the changes in structure, electronic properties, and catalytic activity of the films as a result of Fe inclusion.The high OER activity and simple synthesis make these Ni-based catalyst thin films potentially useful for incorporating with semiconductor photoelectrodes for direct solar-driven water splitting. Towards this goal, we use in situ spectroelectrochemistry to quantify the optical properties of the catalyst at electrode potentials where water oxidation is taking place. We propose a simple model of the composite semiconductor-catalyst system that accounts for parasitic optical absorption in the catalyst layer and calculate a figure-of-merit as a function of thickness to inform composite semiconductor-catalyst device design.(Trotochaud, L.; Ranney, J.K.; Williams, K.N.; Boettcher, S.W. J. Am. Chem. Soc. 2012  , 134, 17253. Trotochaud, L.; Mills, T.J.; Boettcher, S.W. J. Phys. Chem. Lett. 2013  , 4, 931.)

Mechanism and application of mixed nickel-iron oxyhydroxide oxygen-evolution electrocatalysts

246th National Meeting (2013)

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