As one of the most efficient, low-cost, and readily available electrocatalysts for oxygen evolution reaction (OER) in alkaline environments, the nickel-iron electrocatalyst is of great significance to commercial water splitting. In this study, NiFe-layered double hydroxide loaded on nickel foam (NiFe-LDH/NF) was synthe-sized via a simple one-step hydrothermal method, whose OER catalytic performance could be successfully optimized by further electrochemical reconstruction. The results show that NF is an effective precursor to loading crystallized Ni(OH)2 nanoparticles during hydrothermal synthesis, leading to the generation of high-performance NiOOH during OER reconstruction. Under the optimal Ni:Fe feeding ratio, Ni2Fe1-LDH/NF requires an ultra-low OER overpotential of 239 mV at 50 mA cm-2 and 260 mV at 100 mA cm-2 , whose Tafel slope is only 64.1 mV dec-1. Impressively, Ni2Fe1-LDH/NF also achieves an ultra-low voltage of 1.44 V at 10 mA cm-2 with excellent long-term stability for overall water splitting. Unlike the previous viewpoint that only Ni species dominate surface reconstruction of NiFe-LDH, in this article the decisive influence related to Fe species on the reconstruction layers' activity and stability is confirmed by electrochemistry, Raman, and XPS analysis during reconstruction process. During OER reconstruction, the surface Ni:Fe ratios can be "self -adaptively" regulated to an appropriate region, thus the stable reconstruction layers rich in NiOOH can be formed as the protective shells for NiFe-LDH. Furthermore, such "self-adaptive" reconstruction, assisted with appropriate initial Ni:Fe feeding ratios, can also stimulate more Ni3+ active sites for OER, benefitting the outstanding catalytic performance of NiFe-LDH/NF for overall water splitting and prospective large-scale application.(c) 2022 Elsevier B.V. All rights reserved.
