Electron Delocalization Boosting Highly Efficient Electrocatalytic Water Oxidation in Layered Hydrotalcites

Developing high-performance oxygen evolution reaction (OER) electrocatalysts is of great importance for sustainable and renewable energy conversion and storage. Here, via delocalizing the electron population around the active sites of layered hydrotalcites, we significantly facilitate the electron donation from the active sites in Cr-doped Ni 0.75 Fe 0.25 (OH) 2.25 and greatly reduce the charge transfer barrier by 1 order of magnitude for high OER activity. The Cr-doped Ni 0.75 Fe 0.25 (OH) 2.25 hydrotalcite nanosheets could thus achieve a small overpotential of 235 mV at 10 mA/cm 2 with an excellent Tafel slope of ∼39 mV/dec. The X-ray absorption fine structure spectroscopy and theoretical calculations reveal that the incorporated Cr ions are substituted for Fe sites in Ni 0.75 Fe 0.25 (OH) 2.25 and the strong overlap of d orbitals between Cr with unpaired d electrons and Fe ions promotes ∼0.3 electron π-donation from Ni 2+ to neighboring Cr (Fe) ions, and then evidently decreases the adsorption free energy of a water molecule to −1.45 eV for efficient OER performance.