Electrocatalytic activity sites for the oxygen evolution reaction on binary cobalt and nickel phosphides

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Binary cobalt and nickel phosphides show high activity and low cost for oxygen reduction reactions (OER).
• The exact active sites and composition-activity relationships in these phosphides remain unclear.
• Understanding these factors is crucial for designing efficient electrocatalysts.

Purpose of the Study:

• To investigate the correlation between composition and OER activity in CoNiP nanocage catalysts.
• To clarify the role of the CoOOH/NiOOH ratio in determining OER performance.
• To elucidate the origin of catalytic activity in CoNiP systems.

Main Methods:

• Systematic investigation of CoNiP nanocages with varying Ni/Co ratios.
• Electrochemical testing to evaluate oxygen reduction reaction (OER) activity.
• Analysis of the generated CoOOH and NiOOH species during catalysis.

Main Results:

• Increasing Ni/Co ratio enhances NiOOH formation, while CoOOH initially increases then decreases.
• Optimal OER activity was achieved at a Ni/Co ratio of 1.5, with an overpotential of 278 mV and Tafel slope of 67 mV dec⁻¹.
• CoNiP catalysts outperformed pure CoP, indicating a synergistic effect between CoOOH and NiOOH.

Conclusions:

• The OER activity of CoNiP is attributed to the synergistic interaction between CoOOH and NiOOH species.
• The optimal Ni/Co ratio is critical for maximizing catalytic performance.
• This research provides insights for designing superior CoNiP-based electrocatalysts.