Why Is Bulk Thermochemistry a Good Descriptor for the Electrocatalytic Activity of Transition Metal Oxides?

It is well known that transition metal oxides can efficiently catalyze electrochemical reactions of interest in electrolyzers and fuel cells. The question is how to describe and rationalize the variations in catalytic activity among a given class of oxides, so that known materials can be improved and new active materials be predicted. In this context, descriptor-based analyses are a powerful tool, as they help to rationalize the trends in catalytic activity through correlations with other properties of the material. Particularly, bulk thermochemistry has long been used to describe the trends in catalytic activity of oxide surfaces. Here we explain the reason for the apparent success of this descriptor on the basis of perovskite oxides and monoxides and the oxygen evolution reaction: essentially, bulk thermochemistry and surface adsorption energetics depend similarly on the number of outer electrons of the transition metal in the oxide. This correspondence applies to a wide number of transition metals and is responsible for the linear relationship between bulk and surface properties that enables the construction of volcano-type activity plots.