High-efficiency oxygen evolution electrocatalysis enabled by Ar/O2 plasma-induced synergistic modifications in NiFe Prussian blue analogue systems

Abstract

The advancement of efficient and durable non-precious-metal oxygen evolution reaction (OER) electrocatalysts is pivotal for progressing green hydrogen generation via water electrolysis. Traditional metal–organic frameworks (MOFs) are constrained by their low conductivity and structural degradation during pyrolysis, hindering electrocatalytic performance. In this study, we introduce a synergistic Ar/O₂ plasma etching approach to reconfigure NiFe Prussian blue analogues (PBA) anchored on nickel foam (NF), simultaneously addressing structural and electronic limitations. The hybrid plasma treatment integrates physical Ar bombardment and chemical O₂ oxidation, selectively eliminating C/N ligands to expose active catalytic interfaces while creating porosity (20–50 nm pores) and stabilizing high-spin Fe³⁺ species. Structural analyses (SEM, TEM, XRD) validate maintained framework integrity alongside optimized surface roughness and mesoporous networks. XPS investigations demonstrate plasma-induced electronic modulation, wherein O₂ plasma oxidizes Fe²⁺ to Fe³⁺ and generates conductive Ni/Fe oxides, thereby refining intermediate adsorption/desorption kinetics. Electrochemical evaluations reveal superior OER activity: the NiFe PBA-Ar/O₂ catalyst attains a low overpotential of 334 mV at 100 mA cm⁻², a reduced Tafel slope of 97 mV dec⁻¹, and remarkable operational stability (40 mV degradation over 20 h at 100 mA cm⁻²), exceeding the performance of both Ar-treated counterparts and pristine NiFe PBA. This work establishes a universal non-equilibrium plasma engineering strategy for designing MOF-derived electrocatalysts, resolving the trade-off between structural robustness and catalytic efficiency for sustainable energy applications.