A biomimetic structural strategy employing needle-like NiOOH anchored cu-doped nickel‑iron-based electrocatalysts for efficient and stable overall water splitting

Developing a cost-effective and high-performance electrocatalyst for efficient water splitting is crucial for the sustainable production of green hydrogen. In this study, a self-supported three-dimensional hierarchical needle-sheet heterostructured bifunctional electrocatalyst NiOOH/NiFeCu_x was designed. First, copper (Cu) was doped into nickel‑iron layered double hydroxide (NiFe LDH) using a simple hydrothermal method. The trace amount of Cu doping enhanced the electrical conductivity while effectively preventing transient electrochemical dissolution of the Cu during reactions in alkaline solutions. Then, the nickel oxyhydroxide (NiOOH) nanoneedle array was anchored onto the surface of NiFeCu_x, constructing a dogail grass-like needle-sheet biomimetic structure to significantly increase and optimize the accessible active surface area. The results demonstrate that NiOOH/NiFeCu_0.2 delivers outstanding performance in 1 M KOH, exhibiting optimal overpotentials of 224.7 ± 2.1 mV for the oxygen evolution reaction and 137.0 ± 2.0 mV for the hydrogen evolution reaction, alongside stable activity after 40 h of continuous operation. When employed as both the anode and cathode for overall water splitting, it achieves a current density of 10 mA cm^-2 at a minimal cell voltage of 1.598 V and maintains stability for over 80 h at 100 mA cm^-2. This study offers a promising strategy for the development of low-cost, high-efficiency electrocatalysts for water splitting.