Nonmetallic Active Sites on Nickel Phosphide in Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Efficient and durable catalysts are essential for the oxygen evolution reaction (OER).
• Nickel phosphides, particularly Ni12P5, have shown promising OER catalytic activity.
• Understanding the reaction mechanism is key to catalyst optimization.

Purpose of the Study:

• To elucidate the microscopic mechanism of the OER on the Ni12P5 surface.
• To identify the active sites and rate-determining steps in the OER process.
• To explore strategies for optimizing OER catalysts based on electronic properties.

Main Methods:

• Density functional theory (DFT) calculations were employed to study the OER mechanism.
• Ab initio molecular dynamics (AIMD) simulations were used to analyze reaction pathways and dynamics.
• Analysis of electronic properties, including charge distribution and adsorption energies.

Main Results:

• Water adsorption preferentially occurs on P atoms, identifying P as the active site for OER.
• AIMD simulations revealed a step-wise dissociation of water molecules.
• The formation of the OOH group was identified as the rate-determining step, with Ni12P5 exhibiting the lowest overpotential.
• A linear relationship was found between the charge of Ni and P sites and the adsorption energies of OH and O intermediates.

Conclusions:

• The nonmetallic P atom is the active site for OER on Ni12P5.
• Ni12P5 demonstrates enhanced OER catalytic activity compared to other nickel phosphides due to its low overpotential.
• The established relationship between site charge and adsorption energy offers a pathway for designing improved OER catalysts.