Metal-organic framework-derived CoP2@N-doped carbon hollow spheres for efficient oxygen evolution reaction

Developing a highly efficient and low-cost electrocatalyst is an important route to overcome the sluggish kinetics of the oxygen-evolution-reaction (OER). In this work, a series of hollow CoP2@N-doped carbon spheres are synthesized by a pyrolysis-phosphidation method. These hollow spheres are evaluated as electrocatalysts for the OER. Benefiting from the synergistic effects between highly active CoP2 and N-doped carbon (NC), the CoP2@NC-700H (pyrolyzed at 700 °C) exhibits outstanding electrocatalytic performances. The as-prepared hollow CoP2@NC-700 spheres tested on nickel foam have an onset potential of 1.36 V and reached a current density of 100 mA cm–2 at a potential of 1.42 V vs. RHE. It can attain a very high current density (600 mA cm–2) at a very low overpotential (265 mV). An alkaline water electrolyzer (Pt/C as cathode and hollow CoP2@NC-700 spheres as anode catalysts) exhibited excellent electrocatalytic activity and durability. As confirmed by experimental results, the CoP2@NC-700H works as a pre-catalyst for OER rather than as an active material.