Oxygen Vacancies Alter Methanol Oxidation Pathways on NiOOH

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The mechanism of methanol oxidation reaction (MOR) on Ni-based catalysts is crucial for electrocatalytic applications but remains controversial.
• Understanding the active sites and reaction pathways is essential for designing efficient catalysts.

Purpose of the Study:

• To elucidate the mechanism of MOR on monometallic Ni-based catalysts in alkaline media.
• To identify the active sites and determine the key intermediates and pathways involved in MOR.

Main Methods:

• In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) to monitor reaction intermediates.
• Density functional theory (DFT) calculations to compute reaction profiles and assess thermodynamic feasibility.

Main Results:

• SEIRAS detected formate and (bi)carbonate, with their distributions dependent on applied potential.
• DFT calculations supported a formate-involving pathway as the primary route, with a parallel pathway to (bi)carbonate at higher potentials.
• Oxygen vacancies were identified as active sites, suppressing deep dehydrogenation and favoring formate formation over CHO or CO.

Conclusions:

• The MOR on Ni-based catalysts in alkaline media predominantly proceeds through formate-involving pathways facilitated by oxygen vacancies.
• These pathways are thermodynamically more favorable than those involving CHO or CO intermediates.
• Defect engineering, specifically utilizing oxygen vacancies, shows promise for enhancing MOR activity and selectivity.