High-Entropy Layered Double Hydroxides for Efficient Methanol Electrooxidation.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic methanol oxidation (MOR) is a key process for hydrogen production, offering an alternative to oxygen evolution reaction (OER).
• Nickel-based catalysts face challenges due to sluggish kinetics and difficulty in breaking C-H bonds, hindering their widespread application.

Purpose of the Study:

• To synthesize and evaluate novel high-entropy layered double hydroxides (HELHs) for electrocatalytic methanol oxidation.
• To investigate the performance and stability of HELHs, particularly focusing on vanadium-doped variants.

Main Methods:

• Synthesis of three HELHs: ZnNiFeCoV-HELH, ZnNiFeCoCr-HELH, and ZnNiFeCoAl-HELH.
• Electrocatalytic performance testing, including potential measurements at 100 mA cm⁻² and stability assessments over multiple cycles.
• Experimental and theoretical investigations to understand reaction kinetics, active species, methanol adsorption, and energy barriers.

Main Results:

• V-HELH demonstrated the lowest potential (1.39 V at 100 mA cm⁻²) compared to Cr-HELH (1.41 V) and Al-HELH (1.44 V).
• V-HELH maintained over 95% formate yield after five cycles, indicating excellent stability.
• V-HELH exhibited the fastest reaction kinetics, a higher concentration of active Ni³⁺ species, and stronger methanol adsorption (-3.31 eV).
• Theoretical calculations revealed that vanadium introduction optimizes the d-band center (-0.54 eV) and lowers the energy barrier for C-H bond cleavage (-1.62 eV).

Conclusions:

• High-entropy layered double hydroxides, especially V-HELH, are highly effective electrocatalysts for methanol oxidation.
• Vanadium's role in optimizing electronic structure and reducing activation energy barriers is crucial for enhanced catalytic activity and stability.
• This research offers valuable insights for designing advanced electrocatalysts for efficient hydrogen production.