Determining the "Best Catalyst" Depends on the Method of Catalyst Evaluation

 http://pubs.acs.org/doi/abs/10.1021/jacs.5b05093

The “Best Catalyst” for Water Oxidation Depends on the Oxidation Method Employed: A Case Study of Manganese Oxides

Ravi Pokhrel, McKenna K. Goetz, Sarah E. Shaner, Xiaoxia Wu, and Shannon S. Stahl^*

Department of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States

J. Am. Chem. Soc., 2015, 137 (26), pp 8384–8387

DOI: 10.1021/jacs.5b05093

Abstract

Manganese oxides are a highly promising class of water-oxidation catalysts (WOCs), but the optimal MnO_x formulation or polymorph is not clear from previous reports in the literature. A complication not limited to MnO_x-based WOCs is that such catalysts are routinely evaluated by different methods, ranging from the use of a chemical oxidant such as Ce⁴⁺, photoactive mediators such as [Ru(bpy)₃]²⁺, or electrochemical techniques. Here, we report a systematic study of nine crystalline MnO_x materials as WOCs and show that the identity of the “best” catalyst changes, depending on the oxidation method used to probe the catalytic activity.