Electrochemically activated NiOOH/NiFeV-LDH@CC for a highly efficient oxygen evolution reaction

The surface reconstruction of NiFe-based layered double hydroxide (LDH) electrocatalysts has been widely studied. The reconstructed NiOOH phase plays a critical role in improving the oxygen evolution reaction (OER) performance of NiFe-based LDHs, but observing the NiOOH phase is difficult because of its instability and exploring the functional mechanism of NiOOH in NiFe-based LDHs remains a great challenge. A simple electrochemical activation was used to synthesize a NiOOH/NiFeV-LDH@CC catalyst consisting of an array of V-doped NiFe-LDH nanosheets on carbon cloth (CC), in which the reconstructed NiOOH phase is the active species. During electrochemical activation, the release of doped V leads to the formation of abundant vanadium vacancy (V V ) and oxygen vacancy (V O ) species, and thus the surface of the NiFe-LDH nanosheets is reconstructed to form NiOOH. Because of the improved intrinsic activity from the NiOOH active phase, and the increased electrical conductivity produced by the abundant V O , NiOOH/NiFeV-LDH@CC has an excellent OER performance in an alkaline solution, with low overpotentials of 209 mV and 241 mV at 20 mA cm −2 and 100 mA cm −2 , respectively. It also has a long-term stability of 80,000 s at a constant current density of 10 mA cm −2 . Using NiOOH/NiFeV-LDH@CC as the anode, an assembled over water splitting (OWS) battery can drive a current density of 20 mA cm −2 (without iR compensation) at a much lower voltage of 1.597 V. At the same time, the electrolytic cell can deliver a current density of 10 mA cm −2 at ~1.55V for more than 80,000 s without significant loss. This electrochemical activation method can be used in future designs of electrocatalysts for OER. Download: Download high-res image (154KB) Download: Download full-size image