Converting surface-oxidized cobalt phosphides into Co₂(P₂O₇)-CoP heterostructures for efficient electrocatalytic...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient, noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) is critical for advancing the hydrogen economy.
• Transition metal phosphides show promise but are hindered by surface oxidation, limiting active site accessibility.

Purpose of the Study:

• To engineer a novel cobalt phosphide-based electrocatalyst with enhanced HER performance.
• To overcome the challenge of surface oxidation in transition metal phosphides for improved electrocatalytic activity.

Main Methods:

• A facile reduction followed by surface phosphorization was employed to create a Co₂(P₂O₇)-CoP heterostructure embedded in N-doped carbon (Co₂(P₂O₇)-CoP/NC).
• Electrochemical performance was evaluated in acidic (0.5 M H₂SO₄) and alkaline (1.0 M KOH) electrolytes.

Main Results:

• The Co₂(P₂O₇)-CoP/NC catalyst demonstrated efficient HER with low overpotentials of 88 mV (acidic) and 97 mV (alkaline) at -10 mA cm^-2.
• Small Tafel slopes of 51 mV dec^-1 (acidic) and 61 mV dec^-1 (alkaline) were recorded, outperforming the parent material and other Pt-free catalysts.
• The enhanced performance is attributed to the synergistic effect at the Co₂(P₂O₇)-CoP interface, boosted by the surface acidity of Co₂(P₂O₇).

Conclusions:

• The developed Co₂(P₂O₇)-CoP/NC material offers a promising, cost-efficient noble-metal-free electrocatalyst for HER.
• Surface engineering strategies, like the one presented, can effectively address challenges in transition metal phosphides for catalysis.
• This work paves the way for designing advanced electrocatalysts for sustainable energy applications.