Comprehensive Structural Descriptor for Electrocatalytic Oxygen Evolution Activities of Iron Oxides
Yuuki Sugawara, Keigo Kamata, Eri Hayashi, Mitsuru Itoh, Yosuke Hamasaki, Takeo Yamaguchi
Abstract
Abstract To determine the structural descriptor of the oxygen evolution reaction (OER) in a wide range of Fe‐based oxides, we investigate Fe 2 O 3 polymorphs. Remarkably, the OER activity of the polymorphs strongly depends on the atomic configurations in the crystals, and shorter Fe−O bond lengths are more beneficial for the OER. DFT calculations reveal that the trend of Fe−O bond length on the Fe 2 O 3 polymorphs exhibits a positive correlation with their energy gaps between the occupied oxygen 2p and the unoccupied iron 3d orbitals, i. e., charge‐transfer energy, which promotes the OER activities of metal oxides. Surprisingly, the relationship between the Fe−O bond length and the OER activity can also be applied to a wide range of previously reported Fe‐based multimetal oxide OER catalysts, regardless of their chemical compositions and categories of crystal structures, including perovskite, spinel, brownmillerite, and other types of oxides. The discovered descriptor is an important guideline for the rational design of Fe‐based oxides with excellent catalytic properties for the OER and contributes to the establishment of a hydrogen society.