Electrochemical catalysts, or substances that speed up the rate of a chemical reaction, are the focus of extensive research for advanced energy applications, including production and storage of hydrogen and electricity, along with remediation of pollutants.

Catalytic materials work by adding electrons to (reduce) or removing them from (oxidize) the target reactant. The catalytic potential is determined by the magnitude of its band gap, i.e., the distance between the native upper electron energies (the valence band) and the conduction band, where the electrons are mobile. When electrons gain sufficient energy to move into the conduction band, a positively charged “hole” that can capture electrons is created (Figure 1).