Small-Size Intermetallic FeMnPt Nanoparticles Electrocatalyst for HER Under Acidic and Alkaline Conditions

Intermetallic FeMnPt nanoparticles with fine sizes (4–7 nm) and ordered phases (L10 and L12) were successfully synthesized by a facile one-step solid-state reaction method. NaCl powder with size less than 10 μm was employed as the solid-state isolate medium and the mass ratio of precursors to NaCl powders was set as 1:300; the solid reaction was done at 780 °C under a reducing atmosphere (90% Ar + 10% H2) for 180 min. The electrocatalytic hydrogen evolution reaction (HER) performances in both acidic and alkaline solutions were tested. Increasing the Mn precursor amounts in the solid-state reaction process would increase the content of Mn and Pt elements, transform the crystal structure from the L10-phase to the L12-phase, and increase the grain sizes of FeMnPt nanoparticles. Comparing the electrocatalytic HER performance of intermetallic FeMnPt nanoparticles in acidic and alkaline solutions, it was found that the L12-FeMnPt nanoparticles with higher Mn and Pt contents presented a low electrocatalytic overpotential and high specific activity in acidic solution. However, the Mn-containing L10-FeMnPt nanoparticles with higher ordering degrees showed low electrocatalytic overpotentials and high electrocatalytic activity in alkaline solution. The electrocatalytic HER stabilities of intermetallic FeMnPt nanoparticles with different components and ordered phases were comparable in acidic and alkaline solutions. This study provides the guidance for discovering highly efficient intermediate HER catalysts for servicing different acidic and alkaline environments.