Designing efficient catalysts and understanding the underlying mechanisms for anodic nucleophile electrooxidation are central to the advancement of electrochemically-driven technologies. Here, a heterostructure of nickel boride/nickel catalyst is developed to enable methanol electrooxidation into formate with a Faradaic efficiency of nearly 100%. Operando electrochemical impedance spectroscopy and in situ Raman spectroscopy are applied to understand the influence of methanol concentration in the methanol oxidation reaction. High concentrations of methanol inhibit the phase transition of the electrocatalyst to high-valent electro-oxidation products, and electrophilic oxygen species (O* or OH*) formed on the electrocatalyst are considered to be the catalytically active species. Additional mechanistic investigation with density functional theory calculations reveals that the potential-determining step, the formation of *CH2O, occurs most favorably on the nickel boride/nickel heterostructure rather than on nickel boride and nickel. These results are highly instructive for the study of other nucleophile-based approaches to electrooxidation reactions and organic electrosynthesis.
Urea electrooxidation reaction (UOR) plays an important
role in
environmental protection and energy regeneration. The extensively
studied nickel-based catalysts exhibit good activity for UOR, but
urea is more prone to be overelectrooxidized to another pollutant
NO
x
– (x = 2, 3). Herein, the Cu/Ni-B interface catalyst is presented. The
introduction of Cu significantly enhances the Faradaic efficiency
of N2 (nearly 70% at 1.70 V versus RHE). Electrochemical
tests and in situ Raman spectroscopy results show that the introduction
of Cu significantly affects the density of OH* species on the catalyst
in the UOR process. It is proposed that with a moderate decrease in
OH* density, the catalyst can provide enough sites for urea molecules
to allow simultaneous adsorption of the two N atoms, facilitating
the process of N-N coupling to form N2. This work is also
instructive for the design of electrocatalysts for other nucleophile
electrooxidation reactions.
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