Borate narrowed band gap of nickel-iron layer double hydroxide to mediate rapid reconstruction kinetics for water oxidation

Nickel-iron layer double hydroxide (NiFe LDH) is deemed as an attractive pre-catalyst to lower the reaction barrier of oxygen evolution reaction (OER). However, the catalytic efficiency of NiFe LDH is always hampered by the slow and incomplete reconstruction during OER process. Herein, a strategy of borate ion (BO33-) regulation is developed to achieve a fast and adequate reconstruction of NiFe LDH. The BO33- is easy to fill the oxygen vacancy in NiFe LDH, which can narrow the band gap of NiFe LDH to realize an efficient reconstruction under OER conditions. DFT calculations demonstrate the enhanced effect of BO33- on adsorption of hydroxyl ion (OH-) to further improve the OER activity. Sequentially, the BO33- decorated NiFe LDH (NiFeB) shows a desirable catalytic activity for OER with an ultralow overpotential of 201 mV to reach a current density of 10 mA cm−2, which is 40 mV lower than the overpotential of pure NiFe LDH. Moreover, membrane electrode assembly cell using anodic NiFeB and cathodic Pt/C for water splitting affords a cell voltage of only 2.0 V to drive a current density of 540 mA cm−2. This work widens the horizon of ion effect on electrocatalysis and offers an effective approach for developing high-active electrocatalysts.