A new Ni-Fe alloy based on recycled hard carbon support for the oxygen evolution reaction in alkaline media

Ni–Fe-based materials are among the most promising non noble electrocatalysts for the oxygen evolution reaction (OER) in anion exchange membrane water electrolyzers (AEMWEs), a key technology for the sustainable production of clean green hydrogen[1-2]. In this work, we introduce a low impact synthesis route that combines earth abundant metals with a hard carbon (HC) support derived from waste hazelnut shells[3]. The method employs a mild citric acid pretreatment of the biomass recovered by waste hazelnuts and a fully water based metal impregnation, significantly reducing hazardous reagents and environmental footprint. It is presented a systematic evaluation of different Ni:Fe weight ratios on the hazelnut derived HC highlights how composition governs porosity, graphitization, metal dispersion, and alloy formation. Variations in composition strongly influenced charge transfer kinetics, active site accessibility, and stability under potential cycling. Among all formulations, the Ni₂Fe₁–HC catalyst exhibited the highest intrinsic OER activity, improved Tafel behavior, and excellent durability during RDE operation, correlating with its superior metal dispersion and optimized HC microstructure. Electrochemical characterization through rotating disk electrode (RDE) in 0.1M NaOH measurements reveals that the Ni₂Fe₁–HC formulation achieves the most favorable balance of activity. The electrocalyst integrated into an AEMWE single cell exhibited superior OER performance compared to bare Ni-foam electrode, confirming the synergistic effect between optimized Ni–Fe ratios and biomass derived carbon supports that can favour metal distribution and electronic transfer.Overall, this study demonstrates a practical and sustainable pathway to high performance Ni–Fe OER catalysts and underscores the potential of agricultural waste derived carbons in advancing efficient, low cost hydrogen production technologies. Acknowledgements The financial support of ENEA within the PNRR POR H2 - Mission 2 – Component 2 – Investment 3.5, is gratefully acknowledged (Project title: “Synthesis and characterization of low-cost alternative catalysts for low-temperature fuel cells). MAN, and MGB thank the financial support of the National Recovery and Resilience Plan (PNRR), Mission 4 Component 2 Investment 1.3, funded from the European Union – Next Generation EU, within the Spoke 6 “Energy Storage of the Extended Partnership (PE2) NEST - Network 4 Energy Sustainable Transition”. Project founded by Investimento 3.5 “Ricerca e sviluppo sull’idrogeno” Progetto Tecnologie innovative per la produzione di H2 clean senza emissioni di CO2 - TIPIC”. References [1] A. Al-Douri, Int. J. Hydrogen Energy,2024,63, 775. [2] P. Wei, ACS Appl. Mater. Interfaces 2020 ,12, 31503. [3] J. Ñanculeo et al, Biochar 2025, 7, 1.