Hydrochloric acid etching induced flower-like NiFe-layered double hydroxide as efficient electrocatalyst for oxygen evolution reaction

To meet the increasing demand for clean energy storage in modern society, the development of efficient and low-cost electrocatalysts that can overcome and accelerate the sluggish kinetics of electrochemical reactions is required. NiFe-Layered Double Hydroxide (NiFe-LDH) is regarded as an effective oxygen evolution reaction (OER) electrocatalyst, but most of the current synthesis methods, such as electrochemical deposition and calcination, are complex and difficult to operate on a large scale. Herein, we report the preparation of NiFe-LDH directly on a NiFe foam substrate using a simple two-step method in which the surface oxide layer is first removed from NiFe foam using a room-temperature hydrochloric acid bath for 10 min, followed by soaking in hydrochloric acid solution at 80 °C for 20 h. The prepared NiFe foam etched by hydrochloric acid for 20 h (NiFe-20-H) exhibited a unique hydrangea flower-like structure with a large surface area and abundant active sites, which is favorable for OER. Combining the structural advantages of large number of exposed active sites, synergistic effects of nickel and iron, and the convenient charge transfer path provided by the NiFe foam, the resulting NiFe-20-H sample achieved a current density of 10 mA cm⁻² at an extremely low overpotential (241 mV) and a small Tafel slope of 44.2 mV dec⁻¹, providing excellent long-term stability in alkaline electrolyte, surpassing pristine NiFe foam reported in our work, as well as many state-of-the-art electrocatalysts and IrO₂. This efficient synthesis of NiFe-LDH provides a new approach for the development of non-noble OER electrocatalysts and has wide application prospects in the field of electrocatalysts.