Synergistically engineered Pt-decorated NiCo phosphide anchored on a Fe-MIL-88-derived MOF support for enhanced hydrogen evolution

A Pt-decorated bimetallic nickel-cobalt phosphide (NiCoP_z) catalyst was prepared on an optimized Fe-MIL-88 framework supported on nickel foam (NF). Fe-MIL-88 was synthesized via a solvothermal method using polyvinylpyrrolidone (PVP) and subsequently annealed at 250–400 °C. A bimetallic NiCo structure was hydrothermally grown on this framework, followed by Pt deposition using table-top magnetron sputtering (TMS) and a final phosphorization to prepare Pt@NiCoP_z/MIL-400. Scanning Electron Microscopy (SEM) revealed interconnected nanosheets anchored to the MIL-derived framework. X-ray Diffraction (XRD) confirmed retention of the MIL-derived structure with NiCoP phases. Transmission Electron Microscopy (TEM) and Scanning (STEM) coupled with Energy-Dispersive X-ray Spectroscopy (EDS) mapping revealed distinct lattice fringes and a homogeneous distribution of Ni, Co, P, and Pt. X-ray Photoelectron Spectroscopy (XPS) confirmed metal-phosphorus bonding, retained Fe-centers, and the persence of Pt, while Brunauer-Emmett-Teller (BET) showed a hierarchical mesoporous structure with an increased surface area. The Pt@NiCoP_z/MIL-400 catalyst required an overpotential of ∼111 mV at 10 mA cm^-2 and ∼181 mV at 100 mA cm^-2 in 0.5 M H₂SO₄ with a Tafel slope of ∼56 mVdec^-1. A 48-h chronoamperometric test showed reasonable stability, although partial detachment of the surface from the substrate was observed. This approach offers a promising route to efficient HER electrocatalysts, where improved interfacial adhesion could further enhance stability.