Oxygen Atom Migration in Ni₂P/TiO₂ Heterostructures Dynamically Regulates the Electrocatalytic CO₂ Reduction Pathway

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Transition metal phosphides (TMPs) are effective electrocatalysts but face challenges in CO₂ reduction due to competing hydrogen evolution.
• Efficiently activating CO₂ and selectively producing valuable products like methane remains a significant hurdle.

Purpose of the Study:

• To develop a novel electrocatalyst for enhanced CO₂ reduction to methane.
• To investigate the role of oxygen doping in modulating the electronic structure of Ni₂P for improved catalytic performance.

Main Methods:

• Fabrication of an O-Ni₂P/TiO₂ nanowire array electrode via impregnation and low-temperature phosphidation.
• Electrocatalytic performance evaluation for CO₂ reduction, including methane production rate and Faraday efficiency.
• In situ infrared spectroscopy and density functional theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• The O-Ni₂P/TiO₂ electrode demonstrated a methane production rate of 1.46 μmol·h^-1·cm^-2 at -0.4 V (vs RHE) with 11.8% Faraday efficiency.
• The catalyst exhibited excellent long-term stability over a 36-hour electrocatalytic process.
• In situ spectroscopy and DFT calculations confirmed the facile formation of key intermediates (CO*, CH₃*) and a lower activation barrier for CHO* formation on the oxygen-doped surface.

Conclusions:

• Oxygen doping in Ni₂P effectively modulates its electronic structure, suppressing hydrogen evolution and promoting CO₂ activation.
• The O-Ni₂P/TiO₂ nanowire array serves as a highly efficient and stable electrocatalyst for CO₂ to CH₄ conversion.
• This work provides a promising strategy for designing advanced electrocatalysts for CO₂ utilization.