Promoting Effects of In₂O₃on Co₃O₄for CO Oxidation: Tuning O₂Activation and CO Adsorption Strength Simultaneously

Abstract

The doping of In2O3 significantly promoted the catalytic performance of Co3O4 for CO oxidation. The activities of In2O3–Co3O4 increased with an increase in In2O3 content, in the form of a volcano curve. Twenty-five wt % In2O3–Co3O4 (25 InCo) showed the highest CO oxidation activity, which could completely convert CO to CO2 at a temperature as low as −105 °C, whereas it was only −40 °C over pure Co3O4. The doping of In2O3 induced the expansion of the unit cell and structural distortion of Co3O4, which was confirmed by the slight elongation of the Co–O bond obtained from EXAFS data. The red shift of the UV–vis absorption illustrated that the electron transfer from O2– to Co3+/Co2+ became easier and implied that the bond strength of Co–O was weakened, which promoted the activation of oxygen. Low-temperature H2-TPR and O2-TPD results also revealed that In2O3–Co3O4 behaved with excellent redox ability. The XANES, XPS, XPS valence band, and FT-IR data exhibited that the CO adsorption strength became weaker due to the downshift of the d-band center, which correspondingly weakened the adsorption of CO2 and obviously inhibited the accumulation of surface carbonate species. In short, the doping of In2O3 induced the structural defects, modified the surface electronic structure, and promoted the redox ability of Co3O4, which tuned the adsorption strength of CO and oxygen activation simultaneously.

Integrated Cobalt Oxide Based Nanoarray Catalysts with Hierarchical Architectures: In Situ Raman Spectroscopy Investigation on the Carbon Monoxide Reaction Mechanism

“…The pre-edge region in the Co K-edge spectrum is observed as a single peak at approximately 7710 eV (Figure 9a), which correspondst ot he 1s!3d electron transition and is attributed to the Co 2 O 3 reference. Ther adial structure functions (RSFs) of Co 3 O 4 attributed to different Co coordination shells are showni nF igure 9b.A ccording to previous studies, [10,38] the first peak corresponds to the CoÀOc oordination shell, but the two CoÀOc oordination shells of the Co 2+ + and Co 3+ + cations coordinated to Oa toms are usually not separated in the Fourier transform moduli of Co 3 O 4 .T he second and third peaks correspond to the CoÀCo coordinations hell, and the fourth peak is attributed to higherC o ÀCo and CoÀOs hells. The highert he valency,t he higher the energy.I no ur work, the absorption edge energy ( % 7730 eV) is highert han that of CoO (7720 eV).…”

“…[36,37] The absorption edge energy is very sensitivet ot he oxidation state. [10] The 3D atomicarrangement over the spinel Co 3 O 4 with surface oxygen vacanciesi ss hown in Figure 9c.T hese resultss uggest that irislike Co 3 O 4 undergoes an expansion of the unit cell and has more structural defects, which promote the formation of a charge imbalance, oxygen vacancies, or unsaturated chemical bonds (the weakened bond strength and the elongated bond length of CoÀO) on the catalyst surface. However, there is ac lear distinction of the intensity of the main absorption edge position at 7730 eV,w hich indicates the presence of disorder in the structure.…”

“…[1,2] Nevertheless, there are still some inevitable disadvantages that need to be overcome,s uch as the requirement of ah igh temperature (300-400 8C) to catalyze the exhaust gas at nearly 100 %c onversion, ai nhomogeneous distribution of active species, and an increasingly high cost. [7,[9][10][11][12][13][14] For instance, Xie et al [13] reported that Co 3 O 4 nanorods with predominantly exposed (110)p lanes calcined at 450 8Cc ould catalyze CO oxidation at temperatures as low as À77 8Ca taspace velocity (SV) of 15 000 mL h À1 g cat À1 . [3][4][5][6][7][8] These studies on the design and synthesis of catalysts are divided into two types:p owder catalysts and monolithic catalysts.…”

Enhancing Catalytic CO Oxidation over Co3O4 Nanowires by Substituting Co2+ with Cu2+

“…In this regard, Cu 2+ is an ideal candidate for substituting Co 2+ in the Co 3 O 4 lattice because the Cu 2+ cation not only is active for CO oxidation, 1,15,16 but also has an ionic radius that is similar to that of the Co 2+ cation (Figure 1). In addition, replacing Co 2+ with Cu 2+ could also modify the intrinsic activity of Co 3+ by changing the bonding environment surrounding Co. 8,[17][18][19][20][21] In this study, we show that replacing Co 2+ with Cu 2+ cations in polycrystalline Co 3 O 4 nanowires greatly enhances their catalytic activity for CO oxidation. The Co 2+ cation…”

Hydrogenation of biomass-derived compounds containing a carbonyl group over a copper-based nanocatalyst: Insight into the origin and influence of surface oxygen vacancies

“…4B, there are two fitted peaks in the spectra of O1s regions, O I and O II , representing two different kinds of oxygen species. The peak at a lower binding energy of 530.7 eV is characteristic of the lattice oxygen bound to metal cations in the spinel structure [66]; the other at 532.3 eV is mainly assigned to surface-adsorbed oxygen species on oxygen vacancies belonging to defect-oxide and surface hydroxyl-like groups adsorbed on metal ions [66][67][68][69]. Correspondingly, the intensity ratio O II /O I can qualitatively estimate the relative abundance of surface oxygen vacancies to some extent.…”