Oxygen vacancy enhanced catalytic activity of reduced Co 3 O 4 towards p -nitrophenol reduction

Chen, Huihui; Yang, Mei; Tao, Shuxia; Chen, Guangwen

doi:10.1016/j.apcatb.2017.03.038

Cited by 181 publications

(91 citation statements)

References 64 publications

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“…The SEM and TEM images of CoOxHy(H), Co3O4, Co3O4(H) and CoO(H) samples are shown in Figure 7. The SEM image of CoOxHy(H) (Figure 7a), indicates the presence of hexagonal platelets and rod-like morphology [48]. The TEM image (Figure 7a1) confirmed the presence of a hexagonal shapes overshadowed by some porous layer [48,49], in agreement with the XRD data.…”

Section: Thermal and Structural Properties Of Catalystssupporting

confidence: 81%

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

2019

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The as-prepared (Co3O4) and hydrazine-treated (Co3O4(H)) cobalt catalysts were prepared using the precipitation method and evaluated at a temperature range of 40–220 °C for preferential oxidation (PROX) of CO in excess hydrogen. An improved surface reducibility with smaller crystallite size was noted on hydrazine-treated cobalt species (i.e., Co3O4(H) catalyst), which indicates some surface transformation. This finding correlates with the surface roughness formation (as depicted by scanning electron microscope (SEM) and transmission electron microscope (TEM) data), which was further confirmed by an increase in the Brunauer–Emmett–Teller (BET) surface area. The mesoporous structure of the Co3O4(H) catalyst remained intact, as compared to that of the Co3O4 catalyst. Interestingly, the in situ treatment of the standalone Co3O4(H) catalyst decreased the maximum CO conversion temperature (T100%) from 160 °C (over Co3O4) to 100 °C, with good selectivity. The Co3O4(H) catalyst showed good stability, with approximately 85% CO conversion at 100 °C for 21 h, as compared to a faster deactivation of the Co3O4 catalyst. However, the Co3O4(H) catalyst was unstable in both CO2 and the moisture environment. Based on the evaluation of spent hydrazine-treated (CoO(H)) cobalt catalyst, the high PROX activity is associated with the formation of Co3+ species as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR) data.

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Section: Thermal and Structural Properties Of Catalystssupporting

confidence: 81%

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

2019

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“…In order to compare our results with other catalysts in the literature, we evaluated the catalytic ability of Ag-decorated SnO 2 by normalizing the κ app values to κ nor [45, 46]. The normalized rate constant κ nor ( κ nor = κ app / c cat , where c cat is the concentration of the catalyst) is a key indicator for estimating catalytic activity.…”

Section: Resultsmentioning

confidence: 99%

One-Pot Green Synthesis of Ag-Decorated SnO2 Microsphere: an Efficient and Reusable Catalyst for Reduction of 4-Nitrophenol

Zhang

Luo

et al. 2017

Nanoscale Res Lett

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In this paper, hierarchical Ag-decorated SnO2 microspheres were synthesized by a facile one-pot hydrothermal method. The resulting composites were characterized by XRD, SEM, TEM, XPS, BET, and FTIR analysis. The catalytic performances of the samples were evaluated with the reduction of 4-nitrophenol to 4-aminophenol by potassium borohydride (KBH4) as a model reaction. Time-dependent experiments indicated that the hierarchical microspheres assembled from SnO2 and Ag nanoparticles can be formed when the react time is less than 10 h. With the increase of hydrothermal time, SnO2 nanoparticles will self-assemble into SnO2 nanosheets and Ag nanoparticles decorated SnO2 nanosheets were obtained. When evaluated as catalyst, the obtained Ag-decorated SnO2 microsphere prepared for 36 h exhibited excellent catalytic performance with normalized rate constant (κ nor) of 6.20 min−1g−1L, which is much better than that of some previous reported catalysts. Moreover, this Ag-decorated SnO2 microsphere demonstrates good reusability after the first five cycles. In addition, we speculate the formation mechanism of the hierarchical Ag-decorated SnO2 microsphere and discussed the possible origin of the excellent catalytic activity.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2204-8) contains supplementary material, which is available to authorized users.

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“…Within the context of Co@600, enhanced activity over pristine commercially sourced Co 3 O 4 can be attributed to the presence of oxygen vacancies. Chen and coworkers have previously reported oxygen vacancy enhanced activity of Co 3 O 4 towards 4NP reduction, wherein pristine Co 3 O 4 exhibited long induction periods and low initial activity, whereas reduced species, denoted by higher Co 2+ content by XPS, were more active [50]. Co@600 exhibits a Co composition of Co 2+ :Co 3+ 47.7%:52.3% as compared with Co 3 O 4 (1:2 Co 2+ :Co 3+ ).…”

Section: Catalytic Reduction Of 4-nitrophenolmentioning

confidence: 98%

A Combined Mechanochemical and Calcination Route to Mixed Cobalt Oxides for the Selective Catalytic Reduction of Nitrophenols

et al. 2019

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Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent; this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas; Co@100, Co@350 and Co@600 (Co@###; # = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.

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Oxygen vacancy enhanced catalytic activity of reduced Co 3 O 4 towards p -nitrophenol reduction

Cited by 181 publications

References 64 publications

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

One-Pot Green Synthesis of Ag-Decorated SnO2 Microsphere: an Efficient and Reusable Catalyst for Reduction of 4-Nitrophenol

A Combined Mechanochemical and Calcination Route to Mixed Cobalt Oxides for the Selective Catalytic Reduction of Nitrophenols

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