Advanced OER catalysts: MnCo-LDH integrated with NiP2 and Ni5P4 metal phosphides for superior water splitting performance

The oxygen evolution reaction (OER) is a critical step in water splitting, essential for renewable energy systems. This study presented advanced OER electrocatalysts composed of manganese‑cobalt layered double hydroxides (MnCo-LDH) integrated with nickel phosphides (NiP ₂ and Ni ₅P ₄). The MnCo-LDH@NiP ₂ and MnCo-LDH@Ni ₅P ₄ composites were synthesized via layer-by-layer electrochemical deposition on steel substrates. Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) confirmed the successful formation and integration of the composites. The MnCo-LDH@NiP ₂ and MnCo-LDH@Ni ₅P ₄ electrodes demonstrated superior OER activity with overpotentials of 276 mV and 318 mV at 100 mA cm ⁻², respectively, significantly lower than 423 mV for MnCo-LDH alone. Tafel slopes of 53.2 mV dec ⁻¹ for MnCo-LDH@NiP₂ and 60.9 mV dec ⁻¹ for MnCo-LDH@Ni ₅P ₄ indicated enhanced reaction kinetics compared to 84.0 mV dec ⁻¹ for MnCo-LDH. Electrochemical impedance spectroscopy (EIS) showed reduced charge transfer resistance ( R _ct) for MnCo-LDH@NiP₂ (0.62 Ω cm ²) and MnCo-LDH@Ni ₅P ₄ (0.77 Ω cm ²), outperforming MnCo-LDH (1.01 Ω cm ²). These findings along with the results from stability test highlighted the potential of MnCo-LDH integrated with nickel phosphides as highly efficient and stable OER catalysts.