Ferromagnetic Hybrid 2D FeS/FeS2 Nanostructures as Electrocatalysts for the Hydrogen Evolution Reaction

The development of highly effective and durable catalysts for the hydrogen evolution reaction (HER) using abundant earth materials is crucial for advancing the hydrogen economy. In this work, we present an approach for synthesizing two-dimensional (2D) combined phase materials with tunable catalytic and magnetic properties. We successfully synthesized ferromagnetic pristine pyrite (FeS 2 ) nanoparticles (NPs) and hybrid 2D troilite (FeS) nanosheets utilizing the hot-filament metal–chemical vapor deposition (HFMCVD) technique. The mixed phase of 2D FeS/FeS 2 exhibited an exceptional HER catalytic performance, achieving a low overpotential of 40 mV at 10 mA·cm –2 current density. Additionally, the magnetic saturation and magnetic moments of the mixed phase 2D FeS/FeS 2 materials were significantly higher compared to pristine FeS 2 NPs. This increase is attributed to a higher density of unpaired electrons and spins in the mixed phase hybrid materials. These enhanced magnetic properties facilitate more efficient electron transfer, leading to superior catalytic performance with low overpotentials during HER. The ferromagnetic 2D FeS/FeS 2 material holds promise as an electrocatalyst for next-generation water splitting as well as energy conversion applications. Moreover, our computational results based on DFT are consistent with the experimental findings.