A Green\nSolvent-Free Approach Synthesis for Rational\nDesigning of a NiFe-Layered Double Hydroxide [NiFe-LDH] Electrocatalyst\nfor Hydrogen Generation

Creating cost-effective, chemically stable electrocatalysts\nto\nimprove the hydrogen evolution reaction (HER) and oxygen evolution\nreaction (OER) remains a major challenge in electrocatalytic water\nsplitting. We synthesized a highly efficient NiFe-layered double hydroxide\n(LDH) electrocatalyst using a solvent-free method. The formation of\nwell-interconnected metal ions with nanospherical architectures created\nan extensive electrochemically active surface area enriched with catalytically\nactive sites, demonstrating synergistic effects. Preserving the suitable\nstoichiometric ratio, such as Ni<sub>6</sub>Fe<sub>4</sub>LDH, was\ncrucial in enhancing the catalytic performance for both the HER and\nOER. The optimal Ni<sub>6</sub>Fe<sub>4</sub>LDH ratio established\noverpotentials of 167 mV (112 mV dec<sup>–1</sup>) for the\nHER and 280 mV (116 mV dec<sup>–1</sup>) for the OER, attaining\na 10 mA cm<sup>–2</sup> current density in 1 M KOH. Moreover,\nNi<sub>6</sub>Fe<sub>4</sub>LDH demonstrated impressive robustness,\nstable up to 90 h with a minor decrease of 4.1 and 4.6% in the current\ndensity for the HER and OER. Notably, in the bifunctional two-electrode\narrangement of Ni<sub>6</sub>Fe<sub>4</sub>LDH/NF||Ni<sub>6</sub>Fe<sub>4</sub>LDH/NF, effective water electrolysis was accomplished, preserving\na stable 10 mA cm<sup>–2</sup> current density at a bias of\n1.64 V for over 140 h, with a slight current loss of 3.9% of the current\ndensity.