Developing a clean and sustainable energy system is a necessary challenge to meet our rising energy demands. Hydrogen, a clean renewable energy source, is a promising alternative to fossil fuels. Through water electrolysis, the production of hydrogen could potentially achieve required fuel and electricity needs with little to no carbon emissions. Pt and Pt-based materials are the most widely studied due to a considerable overpotential; however, because of high costs and scarcity they are impractical for long-term use. Two-dimensional van der Waals materials are noteworthy electrocatalysts for the hydrogen evolution reaction (HER) because they have high surface area and metallic conductivity. Fe3GeTe2 (FGT) is notable since it is a cleavable and stable 2D material down to the monolayer, preserving metallic character. Very recently, Fe5Ge2Te2 (FG2T), a new exfoliable ferromagnet, was discovered that may have favorable results as well. In this work, we explore and demonstrate the potential of Fe3GeTe2 and Fe5Ge2Te2 as an effective HER electrocatalyst. FGT and FG2T were both synthesized by mixing high-purity elements in a stoichiometric ratio in a glove box. The mixture was sealed under vacuum in a quartz tube before placement into a furnace. Both were annealed at 800 oC followed by slow cooling. Phase purity of the samples were examined by a powder X-ray diffractometer and Rietveld refinement. FGT bulk powder, sonicated powder, and spark plasma sintering (SPS) pellet had HER activities of -0.337 eV, -0.222 eV, and -0.105 eV respectively in an acid media. These results indicate the structure-dependency of HER activity, with the SPS pellet closest to that of Pt (-0.09 eV). This is because a pellet electrode is the densest, giving more active sites for electrocatalysis. These studies show that FGT’s basal plane has HER activity without resorting to chemical modifications, giving insight into the use of 2D ferromagnets for energy storage and conversion.

Magnetic vdW materials for the hydrogen evolution reaction

ACS Fall 2020 Virtual Meeting

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