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

• Fe-MIL-88 annealed at 400°C serves as an optimized MOF support on Ni foam. • NiCoP z nanosheets grown on MIL-400 improve HER activity via bimetal synergy. • Pt sputtering enhances charge transfer and lowers HER overpotential. • Pt@NiCoP z /MIL-400 shows 111 mV@10 mA cm -2 and 56 mV dec -1 Tafel slope. 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), then 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 Pt, while Brunauer-Emmett-Teller (BET) showed a hierarchical mesoporous structure with 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 H 2 SO 4 with a Tafel slope of ∼56 mVdec -1 . A 48-h chronoamperometric test showed reasonable stability, though partial detachment of the surface from the substrate was observed. This approach offers a route to efficient HER, where improved interfacial adhesion could further enhance stability.