Toward iron upcycling for green hydrogen: target engineering for powder-derived iron-based nanoparticles by laser ablation in water

Developing sustainable and cost-effective oxygen evolution reaction (OER) electrocatalysts is urgently required to overcome the cost and critical raw material status of the benchmark iridium and ruthenium-based catalysts. To address this challenge, iron-based nanostructures represent promising alternatives due to their abundance, low cost and potential catalytic activity. Herein, we propose a proof-of-concept study toward future iron upcycling approaches through the synthesis of iron-based nanoparticles by pulsed laser ablation in water. Custom-made iron targets were fabricated from commercial iron (Fe) powders and polymethyl methacrylate (PMMA) employing different Fe:PMMA weight ratios. A bulk iron target was employed as a reference material. A comprehensive physicochemical characterization revealed a strong influence of the target composition on nanoparticles formation and phase evolution. While nanoparticles generated from the bulk target predominantly exhibited the hematite phase, the powder-based targets produced mixed-phase iron-based nanoparticles. Electrochemical investigations demonstrated a competitive OER activity with the nanoparticles obtained from Fe:PMMA 1:2 target showing an overpotential of 335 mV at 10 mA/cm 2 with a deposited total mass loading of ∼47 µg cm −2 . These findings demonstrate the feasibility of tailoring iron-based nanostructures through a versatile powder-based target engineering approach, providing a promising route toward circular manufacturing through iron upcycling for green hydrogen applications.