Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe₂O₃ from First Principles

The challenge of improving the efficiency of photo-electrochemical devices is often addressed through doping. However, this strategy could harm performance. Specifically, as demonstrated in a recent experiment, doping one of the most widely used materials for water splitting, iron (III) oxide (Fe₂O₃), with niobium (Nb) can still result in limited efficiency. In order to better understand the hazardous effect of doping, we use Density Functional Theory (DFT)+U for the case of Nb-doped Fe₂O₃. We find a direct correlation between the charge of the dopant, the charge on surface of the Fe₂O₃ material, and the overpotential required for water oxidation reaction. We believe that this work contributes to advancing our understanding of how to select effective dopants for materials.