Tailoring Competitive Adsorption Sites by Oxygen‐Vacancy on Cobalt Oxides to Enhance the Electrooxidation of Biomass

Abstract

The electrooxidation of 5‐hydroxymethylfurfural (HMF) offers a promising green route to attain high‐value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH− on the electrode surface. An in‐depth understanding of these adsorption sites and reaction processes on electrocatalysts is fundamentally important. Herein, the adsorption behavior of HMF and OH−, and the role of oxygen vacancy on Co3O4 are initially unraveled. Correspondingly, instead of the competitive adsorption of OH− and HMF on the metal sites, it is observed that the OH− can fill into oxygen vacancy (Vo) prior to couple with organic molecules through lattice oxygen oxidation reaction process, which could accelerate the rate‐determining step of the dehydrogenation of 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA) intermediates. With the modulated adsorption sites, the as‐designed Vo‐Co3O4 shows excellent activity for HMFOR with the earlier potential of 90 and 120 mV at 10 mA cm−2 in 1 m KOH and 1 m PBS solution. This work sheds insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel electrocatalysts to modulate the multi‐molecules combined adsorption behaviors.

Selective Electrooxidation of Biomass‐Derived Alcohols to Aldehydes in a Neutral Medium: Promoted Water Dissociation over a Nickel‐Oxide‐Supported Ruthenium Single‐Atom Catalyst

“…As shown in the LSV curves (Figure S21), a current density of 97.2 mA cm À 2 is achieved at 1.5 V in 1.0 M KOH, which is 3.2 times than that in 1.0 M PBS, indicating that the alkaline medium facilitates the HMFOR, in consistence with the previous result. [24] As proposed by Koper and colleagues, the higher activity of alcohol oxidation in alkaline medium can be attributed to base-catalyzed deprotonation of alcohol, which results in the formation of more reactive alkoxide species. [21,22] Figure 3f shows the product distribution of the HMFOR in 1.0 M KOH.…”

“…Indeed, as reported by Wang et al, at neutral pH, oxidation of aldehyde groups of HMF can be largely suppressed, as evidenced by the formation of 2,5-diformylfuran (DFF) intermediate and the accumulation of formyl-2furancarboxylic acid (FFCA), indicating that neutral pH is more favorable for aldehyde synthesis. [24] Nevertheless, the activity of BDAORs in neutral/near-neutral medium is orders of magnitude lower than that in alkaline medium, [18,24] representing a major obstacle of BDAORs to aldehyde at neutral pH.…”

Insights into the activity of nickel boride/nickel heterostructures for efficient methanol electrooxidation

“…In 1 M KOH electrolyte (Fig. 3a ), the response appearing in the high frequency region after 1.36 V is associated with the oxidation of the electrode inner 30 . The response appearing in the low frequency region is related to the nonhomogeneous charge distribution caused by surface oxidized species 30 , 31 .…”

Conversion of Catalytically Inert 2D Bismuth Oxide Nanosheets for Effective Electrochemical Hydrogen Evolution Reaction Catalysis via Oxygen Vacancy Concentration Modulation

“…For the Pl-60, the peaks were located at 158.2 and 163.5 eV, corresponding to a 0.5 eV shift. This type of down shifting is due to lowering the coordination of Bi atoms by the formation of plasma induced oxygen vacancies [ 58 , 67 ].

Fig.

…”

“…4 b), where the O 1s state located at around 530.8 eV is associated with V o or more accurately the change of chemical states of the lattice oxygen resulted by the formation of oxygen vacancies, and the one at 529.6 eV corresponds to lattice oxygen [ 62 , 68 ]. Although the assignment of V o has been disturbed by attached the hydroxyls, water molecules, and organic contaminants [ 69 ], the same fabrication, storage, and treatment conditions of the samples ensure that the increase of the high-energy core level of O 1s after plasma irradiation were ascribed by surface oxygen vacancies formation [ 58 , 70 , 71 ]. Therefore, we did not deconvolute the oxygen peak at 530–533 eV but exclude the contributions originated from the hydroxyls and the adsorbed water molecules by taking the non-treated sample Pl-0 as the baseline to calculate the generated oxygen vacancy concentrations resulted by the plasma irradiations.…”