Iridium catalysts are highly active for the oxygen evolution reaction [1], [2] in proton exchange membrane water electrolyzers. The high cost of iridium, however limits the widespread use of these devices. One approach to solve this issue is to use small iridium particles or thin iridium coatings supported over various inexpensive substrates to maximize the mass activity and minimize the total amount of iridium required. The challenge is to identify the substrate material which exhibits the optimal interactions with iridium, stabilizing the thin iridium coating while maintaining the high activity for the oxygen evolution reaction of the supported iridium. In this research, we used density functional theory to calculate the adsorption energy of a single iridium atom, small iridium islands, and a complete iridium overlayer onto transition metals and transition metal compounds, including carbides, borides and nitrides, to estimate the stability of the iridium supported on these materials. Across FCC (111) and BCC (110) transition metal substrates, we found that the BCC substrates bind Ir more strongly than FCC substrates. Furthermore, we also found that the adsorption energy of iridium correlates with substrate d-band center and lattice constant. For the transition metals compounds, it was found that a carbon terminated surface of a carbide support showed stronger iridium binding in comparison to that on a metal terminated surface. On all transition metal compound supports, the binding of iridium weakens with increasing iridium coverage. By using these DFT results, we will discuss the design of different catalyst support such as transition metals, carbides, borides and nitrides for oxygen evolution reaction catalysts.
