Porous superstructures constructed from ultrafine FeP nanoparticles for highly active and exceptionally stable hydrogen evolution reaction

Abstract

Aiming at providing an efficient strategy to design non-precious metal electrocatalysts with high electrocatalytic activity and simultaneously long-term stability for the hydrogen evolution reaction (HER), we report in this work the fabrication of porous FeP microsphere superstructures (SSs) made up of ultrafine FeP NPs through a self-templating gas–solid phosphorization reaction of urchin-like FeOOH microspheres. Since the ultrafine FeP NPs are arranged in a loose and isolated manner instead of being densely packed like in the resulting FeP microspheres, the FeP SS with high porosity exhibits highly active and exceptionally stable HER performance even at a low mass loading of the electrocatalyst. At a mass loading of 0.566 mg cm⁻², an overpotential of 66 mV is achieved. At a mass loading as low as 0.142 mg cm⁻², the highest mass activity of up to 70.4 mA mg⁻¹ with a η₁₀ of 102 mV is achieved, which is superior to that of all other non-precious metal electrocatalysts. The chronopotentiometry (CP) test at a current density of 10 mA cm⁻² for 24 h shows that the overpotential increases slightly from 66 mV to 80 mV, indicating a fairly stable HER process.