Ni-Incorporated FeCo Layered Double Hydroxides with Nanosheet/Nanoneedle Hybrid Morphology for LOM-Assisted Bifunctional Water Splitting

Abstract

Water electrolysis for hydrogen production is a clean energy technology, but the anodic oxygen evolution reaction (OER) inherently exhibits slow kinetics. Here, we synthesized FeCo layered double hydroxides on nickel foam (FeCo LDHs/NF) with different Fe/Co ratios via a one-step hydrothermal method. At Fe/Co = 1.5:1, FeCo LDHs/NF-d shows a hybrid nanosheet/nanoneedle morphology with abundant vacancy defects. Partial dissolution of the NF incorporates Ni into the LDH layers. The catalyst displays excellent bifunctional behavior in 1 M KOH, with low overpotentials of 187 mV (OER) and 155 mV (HER) at 10 mA cm–2, with no significant decay after 50 h. In situ infrared spectroscopy and pH dependence confirm a dual-pathway mechanism involving the adsorbate evolution mechanism and the lattice oxygen oxidation mechanism. As bifunctional electrodes in a symmetric two-electrode cell, FeCo LDHs/NF-d achieves 10 mA cm–2 at 1.59 V in 1 M KOH and exhibits robust stability for 96 h at 50 mA cm–2. Density functional theory calculations demonstrate that Ni doping induces an upward shift of the d-band center, enhances *OH adsorption, and reduces the OER rate-determining step barrier from 2.10 to 1.61 eV. This work proposes an effective route to develop durable nonprecious bifunctional electrocatalysts for sustainable hydrogen production.