NiFeOxHy with electron-deficient Ni2+ for oxygen evolution in mild media

NiFe-layered double hydroxide (NiFe–OH) is one of the most promising candidate materials for the oxygen evolution reaction (OER) in an alkaline electrolyte . However, it is difficult to be oxidized into Ni 3+ FeOOH active species with high valence Ni under mild conditions; thus, the activity under mild conditions is inferior. We report here that NiFe–OH is converted to amorphous NiFeO x H y (a3-NiFe-OH) with easily oxidized electron-deficient Ni 2+ after pre-oxidation in an alkaline solution boosts the OER performance under mild conditions. The amorphous structure of a3-NiFe-OH also enlarges the electrochemically active area to expose more active sites. It merely needs an overpotential of 350 mV at 10 mA cm −2 in 0.1 M KHCO 3 electrolyte. The corresponding Tafel slope is as low as 89 mV dec −1 . This work affords a strategy for developing (near) neutral OER catalysts.