Multishelled FeCo@FeCoP@C Hollow Spheres as Highly Efficient Hydrogen Evolution Catalysts.

Active nonprecious metal-based hydrogen evolution reaction (HER) electrocatalysts are critical for the clean and sustainable generation of hydrogen. Here, we synthesized multishelled FeCo@FeCoP@C hollow spheres by the carbonization and phosphorization of the FeCo-MIL-88 metal-organic framework. Owing to both composition (FeCo mixed phosphide) and morphology (multishelled morphology) effects, the as-obtained FeCo@FeCoP@C exhibits excellent HER performance with a low overpotential of 65 mV to achieve an HER current density of 10 mA cm-2 and high stability in acidic solution. Density functional theory calculations show that the FeCoP have the optimal hydrogen absorption energy than that of FeP and CoP. The carbon shell prevents the oxidation of the phosphides, and the FeCo core provides better conductivity. Our work provides a new method to synthesize multishelled structure catalysts, which has potential applications in the further hydrogen production.