Developing improved catalysts for the oxygen evolution reaction (OER) is a crucial step for advancing technology in renewable fuels, e.g. solar water splitting. In this work, we identify CoTiOx as a novel nonprecious metal catalyst for the OER and explore the effect of temperature treatments on its activity, structure, and electronic state. Using a simple and scalable sol-gel synthesis, this catalyst can be deposited on a wide variety of conductive substrates. Physical and electronic characterization of the most active CoTiOx catalyst, prepared at low temperature (150 degrees C), reveals an amorphous thin film structure with an oxidation state similar to that of other active cobalt catalysts. Electrochemical testing and X-ray absorption spectroscopy show that the more active, amorphous catalysts undergo greater changes in oxidation state during OER than the less active, crystalline catalysts. Extended electrochemical testing shows that the catalysts are stable in basic electrolyte. (C) 2015 The Electrochemical Society. All rights reserved.