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(a) XPS spectra of the MnO 2 @NiCo 2 O 4 nanowire and O 1s XPS spectra (inset); (b-d) XPS survey scan of Mn 2p, Co 2p and Ni 2p regions, respectively.
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In this work, we have rationally designed and originally developed a novel monolith de-NOx catalyst with nickel foam as the carrier and three dimensional hierarchical MnO2@NiCo2O4 core-shell nanowire arrays in-situ grown on the surface via a two-step hydrothermal process with a post calcination treatment. The catalysts were systematically examined...
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... homogeneously aligned and separated apart adequately. The high-magnication SEM image (Fig. 1d) clearly reveals that the surface layer of each nanowire is made up of numerous small nanoparticles, and the nanowire is about 100 nm in diameter and 600-700 nm in length. A similar morphology can be observed on the Ni-Co basic carbonate precursors ( Fig. S3a and b, ESI †), suggesting that the well- dened array structure is well retained and MnO 2 nanoparticles preferentially in situ deposit on the surface of Ni-Co nanowires and forms a uniform coverage. The EDS spectrum (Fig. S2b, ESI †) of the MnO 2 @NiCo 2 O 4 nanowires also conrms that the NiCo 2 O 4 nanowires have been coated by the MnO 2 ...
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... XPS studies were also conducted to determine the chemical composition and elemental chemical state on the surface of MnO 2 @NiCo 2 O 4 @Ni foam. Fig. 3a shows the pres- ence of O, Mn, Co, Ni elements within the nanowire, consistent with the results of EDS and element mapping. Fig. 3a-d show the XPS survey scan of O 1s, Mn 2p, Co 2p and Ni 2p regions, respectively. The XPS spectra of O 1s (Fig. 3a) could be tted into two peaks denoted as O a and O b . Normally, the peak located at ...
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... XPS studies were also conducted to determine the chemical composition and elemental chemical state on the surface of MnO 2 @NiCo 2 O 4 @Ni foam. Fig. 3a shows the pres- ence of O, Mn, Co, Ni elements within the nanowire, consistent with the results of EDS and element mapping. Fig. 3a-d show the XPS survey scan of O 1s, Mn 2p, Co 2p and Ni 2p regions, respectively. The XPS spectra of O 1s (Fig. 3a) could be tted into two peaks denoted as O a and O b . Normally, the peak located at 531.3-532 eV (denoted as O a ) is the characteristic peak of surface-adsorbed oxygen from the oxide defects or hydroxyl groups, and the ...
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... the chemical composition and elemental chemical state on the surface of MnO 2 @NiCo 2 O 4 @Ni foam. Fig. 3a shows the pres- ence of O, Mn, Co, Ni elements within the nanowire, consistent with the results of EDS and element mapping. Fig. 3a-d show the XPS survey scan of O 1s, Mn 2p, Co 2p and Ni 2p regions, respectively. The XPS spectra of O 1s (Fig. 3a) could be tted into two peaks denoted as O a and O b . Normally, the peak located at 531.3-532 eV (denoted as O a ) is the characteristic peak of surface-adsorbed oxygen from the oxide defects or hydroxyl groups, and the other centered at 529.6-530.1 eV is ascribed to lattice oxygen. 50 The abundance of O a in MnO 2 @NiCo 2 O 4 @Ni ...
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... the peak located at 531.3-532 eV (denoted as O a ) is the characteristic peak of surface-adsorbed oxygen from the oxide defects or hydroxyl groups, and the other centered at 529.6-530.1 eV is ascribed to lattice oxygen. 50 The abundance of O a in MnO 2 @NiCo 2 O 4 @Ni foam may be benecial to the NH 3 -SCR of NO. 50 The Mn 2p 3/2 spectra (Fig. 3b) typical reduction peak of Mn 3 O 4 to MnO, 51,54 demonstrates that there are abundant manganese oxides on the surface of the catalyst, and this may be due to the fact that the unique hier- archical structure of Ni-Co nanowires provides large specic areas and makes it easier to deposit more manganese oxides on the surface. It has been ...
Citations
... Zhu et al. 25 investigated the dual interfacial effects between PtFe and FeO x in each nanowire (NWs) as well as the interaction between NWs and TiO 2 support on the PtFe-FeO x /TiO 2 catalyst, and discovered their interfacial synergy in CO oxidation. Liu et al. 26 designed a hierarchical MnO 2 @NiCo 2 O 4 @Ni foam catalyst, and found that the threedimensional core-shell structure maximizes the interaction between NiCo 2 O 4 and MnO 2 , consequently improving the performance of NH 3 -SCR at low temperature. Zhang et al. 27 constructed AgO/CeSnO x tandem catalysts and studied the synergistic effects between AgO and CeSnO x dual sites for selective oxidation of NH 3 . ...
Multicomponent oxides are intriguing materials in heterogeneous catalysis, and the interface between various components often plays an essential role in oxidations. However, the underlying principles of how the hetero-interface affects the catalytic process remain largely unexplored. Here we report a unique structure design of MnCoOx catalysts by chemical reduction, specifically for ethane oxidation. Part of the Mn ions incorporates with Co oxides to form spinel MnxCo3-xO4, while the rests stay as MnO2 domains to create the MnO2-MnxCo3-xO4 interface. MnCoOx with Mn/Co ratio of 0.5 exhibits an excellent activity and stability up to 1000 h under humid conditions. The synergistic effects between MnO2 and MnxCo3-xO4 are elucidated, in which the C2H6 tends to be adsorbed on the interfacial Co sites and subsequently break the C-H bonds on the reactive lattice O of MnO2 layer. Findings from this study provide valuable insights for the rational design of efficient catalysts for alkane combustion.
... The broad peak appearing in the spectrum has been ascribed to Mn 2p 3/2 , which on deconvolution reveals the co-existence of a mixed valence states: Mn 4+ (646.2 eV) and Mn 3+ (641.6-642.3 eV)[50][51][52][53]. The characteristic peak at about 529.2 eV in the high-resolution O-1s spectrum, shown infigure 4(d), is attributed to a metal-oxygen bond, while the second peak at a binding energy of approximately 531 eV is ascribed to / or hydroxyl ions absorbed on the surface[54]. ...
Present study reports electrochemical behavior of BiNi 0.6 Mn 0.4 O 3 nanostructures synthesized via citric acid and ethylene glycol assisted hydrothermal process at low temperature calcination of 400 o C. Raman spectroscopy and Rietveld refinement have confirmed BiNi 0.6 Mn 0.4 O 3 to crystallize in tetragonal phase with P4 ̅21c space group symmetry. X-ray photoelectron spectroscopic analysis showed the presence of ‘B’ cations, Ni and Mn in (+2) and (+4) oxidation states, respectively, which mainly contributed to faradaic reactions as observed in CV curves. The specific capacitance of BiNi 0.6 Mn 0.4 O 3 electrodes has been found to be ~243 F/g at the current density of 1 A/g in a 6 M KOH aqueous solution. The nanostructured electrodes showed a cyclic stability of ~ 70% after 4000 charge-discharge cycles at the current density of 6 A/g.
... eV corresponded to Mn 3+ , and the two peaks centered at 645.91 and 654.52 eV were assigned to Mn 4+ [48,51]. As an intermediate ion, Co 3+ ion and Mn 3+ ion could significantly promote the redox cycle during the catalytic process due to their strong conversion ability between various valence states of Co and Mn ions [52,53]. As shown in Figure 3d, the O 1s spectrum was fitted into three peaks located at 529.84, 531.54, and 531.95 eV, which were assigned to Co-O, Ni-O and Mn-O, respectively [54]. ...
Given the serious harm of toxic phenol to human health and the ecological environment, it is urgent to develop an efficient, low-cost and sensitive nanoenzyme-based method to monitor phenol. MOF-derived nanozyme has attracted wide interest due to its hollow polyhedra structure and porous micro-nano frameworks. However, it is still a great challenge to synthesize MOF-derived multimetal synergistic catalytic nanoenzymes in large quantities with low cost. Herein, we reported the synthetic strategy of porous hollow CA-CoNiMn-CLDHs with ZIF-67 as templates through a facile solvothermal reaction. The prepared trimetallic catalyst exhibits excellent peroxidase-like activity to trigger the oxidative coupling reaction of 4-AAP and phenol in the presence of H2O2. The visual detection platform for phenol based on CA-CoNiMn-CLDHs is constructed, and satisfactory results are obtained. The Km value for CA-CoNiMn-CLDHs (0.21 mM) is lower than that of HRP (0.43 mM) with TMB as the chromogenic substrate. Because of the synergistic effect of peroxidase-like activity and citric acid functionalization, the built colorimetric sensor displayed a good linear response to phenol from 1 to 100 μM with a detection limit of 0.163 μM (3σ/slope). Additionally, the CA-CoNiMn-CLDHs-based visual detection platform possesses high-chemical stability and excellent reusability, which can greatly improve economic benefits in practical applications.
... With regard to the morphological architectures of CuO nanoparticles (NPs), plate-, needle-, and wire-shaped arrangements and nano-cuboids, -platelets, -rods, and -belts with preferentially oriented crystal planes have been reported [44][45][46]. ...
The link between morphology and properties is well-established in the nanoparticle literature. In this report, we show that different approaches in the synthesis of copper oxide can lead to nanoparticles (NPs) of different size and morphology. The structure and properties of the synthesized NPs are investigated with powder X-ray diffraction, scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). Through detailed SEM analyses, we were able to correlate the synthetic pathways with the particles’ shape and aggregation, pointing out that bare hydrothermal pathways yield mainly spheroidal dandelion-like aggregates, whereas, if surfactants are added, the growth of the nanostructures along a preferential direction is promoted. The effect of the morphology on the electronic properties was evaluated through DRS, which allowed us to obtain the electron bandgap in every system synthesized, and to find that the rearrangement of threaded particles into more compact structures leads to a reduction in the energy difference. The latter result was compared with Density Functional Theory (DFT) computational models of small centrosymmetric CuO clusters, cut from the tenorite crystal structure. The computed UV-Vis absorption spectra obtained from the clusters are in good agreement with experimental findings.
... Compared with MnO x / CNT and MnO x /TiO 2 catalysts, nf-MnO x @CNT catalyst showed excellent H 2 O resistance. Additionally, Liu et al. 94 prepared MnO 2 @NiCO 2 O 4 core−shell nanorods with nickel foam as carrier. The Ni−Co nanorods had high specific surface area and there was an excellent synergy among Ni, Co, and Mn oxides, thus promoting the excellent low-temperature activity and H 2 O resistance of the catalyst. ...
The treatment of NO x has become an urgent issue due to it being difficult to degrade in air and its tremendous adverse impact on public health. Among numerous NO x emission control technologies, the technology of selective catalytic reduction (SCR) using ammonia (NH3) as the reducing agent (NH3-SCR) is regarded as the most effective and promising technique. However, the development and application of high-efficiency catalysts is severely limited due to the poisoning and deactivation effect by SO2 and H2O vapor in the low-temperature NH3-SCR technology. In this review, recent advances in the catalytic effects from increasing the rate of the activity in low-temperature NH3-SCR by manganese-based catalysts and the stability of resistance to H2O and SO2 during catalytic denitration are reviewed. In addition, the denitration reaction mechanism, metal modification, preparation methods, and structures of the catalyst are highlighted, and the challenges and potential solutions for the design of a catalytic system for degenerating NO x over Mn-based catalysts with high resistance of SO2 and H2O are discussed in detail.
... where, [ ] in and [ ] out represent the inlet and outlet concentrations of different gases at steady state, respectively. At high GHSV, assuming that the NH 3 -SCR catalytic reaction is not controlled by diffusion but by the dynamic mode, the normalized SCR reaction rate constant per specic surface area of the catalyst can be calculated according to the following equation: 16,17 Rate ...
... 37 The lower activation energy of BC-10Ce-2La/TiO 2 also indicates that this catalyst requires less energy and is more likely to undergo catalytic reactions. 16,17 To further understand the catalytic rate of different catalysts, the TOF value per Ce atom was calculated in the range of 200-270°C. In the experiments, the maximum conversion of NO x is controlled below 20% in the whole temperature range to eliminate the inuence of diffusion. ...
High-temperature 10Ce-2La/TiO2 catalysts for selective catalytic reduction of NO with NH3 were prepared by the ball milling, impregnation and co-precipitation methods and their catalytic performance was compared. The effects of different starting materials of the ball milling method on the catalytic activity were investigated. The results showed that the 10Ce-2La/TiO2 catalyst prepared by the ball milling method using carbonates as starting materials exhibited the highest NO conversion, which was more than 80% in the temperature range of 330-550 °C. The as-prepared catalysts were characterized by XRD, TEM, and XPS. Results showed that the ball milling prepared 10Ce-2La/TiO2 had the advantages of uniform active site distribution, high oxygen storage capacity, and high Ce3+ and Oα ratio. The results of NH3-TPD and H2-TPR showed that the ball milling method not only improved the redox ability but also increased the quantities and concentration of the acidic sites. The green production and economically viable concept of this process provides a new solution for the production application of industrial catalysts.
... The low-temperature characteristics of NH 3 -SCR catalysts have been studied extensively at home and abroad and have made a significant progress [29]. According to the active components, the SCR catalysts can be divided into three categories: noble metal catalysts (platinum (Pt), palladium (Pd), Argentum (Ag), etc.) [30][31][32], transition metal oxide catalysts (Mn, Ferrum (Fe), Nickel (Ni), Vanadium (V), Copper (Cu), Chromium (Cr), Cobalt (Co), Cerium (Ce), etc.) [33][34][35][36][37], and transition metal ion exchange zeolite catalysts [29]. Although noble metals have the excellent catalytic activity at low temperatures [38], they are not widely used due to their high prices, shortage of resource, narrow operation windows, and poor sulfur poisoning resistance [39]. ...
Selective catalytic reduction technology has been widely used to remove NO x. However, the development of low-temperature selective catalytic reduction catalysts with high removal efficiency still faces severe challenges. This paper reviews the progress of research on Mn-based catalysts for selective catalytic reduction of NO x at low temperatures. Catalysts were divided into three categories: single manganese oxide catalysts, polymetallic oxide catalysts, and supported Mn-based catalysts. In the part of single manganese oxide catalysts, the effects of oxidation state, crystallinity, specific surface area, and species morphology on catalytic activity were systematically reviewed. In the part of polymetallic oxides catalysts, Mn-based catalysts were studied from the aspects of preparation strategy, catalytic performance, resistance to H 2 O and SO 2 , and broadening the operating temperature window. In the part of supported metal oxides, Mn-based catalysts supported on Al 2 O 3 , TiO 2 , CeO 2 , activated carbon fibers, and carbon nanotubes were reviewed. In addition, the mechanisms of hydrothermal deactivation, chemical deactivation, sulfur poisoning, and hydrocarbon poisoning of Mn-based catalysts were studied. Finally, the prospects and future directions for the development of Mn-based low-temperature selective catalytic reduction catalysts are presented.
... Besides, the Co/Ni element played an effective role in delaying the poison effects by SO 2 , while the mixed oxides would still loss its SCR activity during a longtime reaction . Most importantly, the design of Mn-based catalysts with micro-crystal morphology (coreshell ( Liu et al., 2015 ), micro-sheet , spinel crystal ( Gao et al., 2019 ), etc.) are the potential ideas to overcome the above poisoning process. ...
One-step synthesis Mn-SnO 2 nanosheet Ni or Co modification SCR performances Promotional mechanism a b s t r a c t NH 3-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis method. Due to its strong oxidation performance, Sn-MnOx was prone to side reactions between NO, NH 3 and O 2 , resulting in the generation of more NO 2 and N 2 O, here most of N 2 O was driven from the non-selective oxidation of NH 3 , while a small part generated from the side reaction between NH 3 and NO 2. Co or Ni doping into Sn-MnOx as solid solution components obviously stronged the electronic interaction for actively mobilization and weakened the oxidation performance for signally reducing the selective tendency of side reactions to N 2 O. The optimal modification resulted in improving the surface area and enhancing the strong interaction between polyvalent cations in Co/Ni-Mn-SnO 2 to provide more surface adsorbed oxygen, active sites of Mn 3 + and Mn 4 + , high-content Sn 4 + and plentiful Lewis-acidity for more active intermediates, which significantly broadened the activity window of Sn-MnOx, improved the N 2 selectivity by inhibiting N 2 O formation, and also contributed to an acceptable resistances to water and sulfur. At low reaction temperatures , the SCR reactions over three catalysts mainly obeyed the typical Elye-rideal (E-R) routs via the reactions of adsorbed l-NH x (x = 3, 2, 1) and B-NH 4 + with the gaseous NO to generate N 2 but also N 2 O by-products. Except for the above basic E-R reactions, as increasing the reaction temperature, the main adsorbed NO x-species were bidentate nitrates that were also active in the Langmuir-Hinshelwood reactions with adsorbed l-NH x species over Co/Ni modified Mn-SnO 2 catalyst.
... It mainly showed that the excellent NOx purification performance and water resistance of 3DH-NM/NF catalyst were due to its three-dimensional layered structure, strong synergistic effect between Mn and Ni species, exposed active sites, enrichment of structural defects and enhancement of surface acidity. Liu et al. [22] prepared a nano-wire array on the graded MnO 2 @NiCo 2 O 4 @Ni foam as a new overall De-NOx catalyst for NH 3 -SCR. While maintaining the stability of the catalyst, both the activation temperature and the optimum denitration temperature decreased by about 120 • C, which was lower than that of the Mn x Co 3− x O 4 particulate catalyst, and the maximum NO conversion rate reached 96%. ...
MnCeOx/NF, Co/MnCeOx/NF and HMoP/Co/MnCeOx/NF catalysts were optimized step by step and used for the selective catalytic reduction (SCR) of NOx with NH3. The catalytic performance, water/sulfur resistances and N2 selectivity of the overall catalyst were significantly improved and maintained during above continuous optimization processes. Firstly, MnCeOx loaded 3D monolithic Ni-foam (MnCeOx/NF) catalysts were investigated using response surface methodology (RSM) method with central composite design (CCD). Regression equations and 3D response surface graphs showed that the model-predicted value was highly in line with experiment-actual result for the catalytic performances synchronously corresponding to load and calcination temperature, calcination and reaction temperature, which obtained 95.7% NOx conversion with 76.7% N2-selectivity at 179.5 °C over the optimal 16.5%MnCeOx/NF catalyst calcinated at 432 °C. Calcination temperature has a great influence on SCR activity that a suitable one increased the surface Mn⁴⁺, Ce³⁺ and chemical adsorption oxygen, while a high one visibly decreased NOx conversion due to the rapid weakened oxygen absorption and lattice oxygen content. The coexistence of typical Eley–Rideal and Fast-SCR reaction mechanisms were found over MnCeOx/NF, while the reaction rate of intermediates changed significantly but also reduced N2-selectivity due to the increased rate of side reactions as reaction temperature increasing. Secondly, among Co-, Ni- or Fe-modified catalysts, the optimized Co/MnCeOx/NF obtain an acceptable H2O and SO2 resistance with stable NOx conversion above 72% within 10 h at 175 °C. Furthermore, phosphomolybdic acid modified Co/MnCeOx/NF catalyst maintained more than 80% N2-selectivity at 275 °C along with almost 100% NOx conversion within 175 °C–275 °C. These advantages synergistically accelerate the overall SCR performances of activity, selectivity and resistance of the optimized HMoP/Co/MnCeOx/NF catalyst.
... The phase purity of nickel cobalt oxide/sulfide was examined using X-ray diffraction. The X-ray patterns of the samples are shown in Fig. 2 [20]. For the nickel-cobalt sulfide, the peaks are located at 31.5, 38.5, 50.4, ...
With the advancement in technology, demand for green energy production is increasing year by year. To meet the increasing demand for green energy, there has been continuous research in a bid to find better materials and efficient ways to generate energy. Transition metals such as Fe, Mo, Ni, etc. based materials have shown great potential to be used as electrocatalysts for water splitting, and the urea oxidation reaction (UOR). In this work, nanostructured nickel-cobalt oxide and nickel-cobalt sulfide were synthesized using a facile hydrothermal method for their applications in water splitting and UOR. It was observed that the properties of nickel-cobalt oxide improved significantly after converting it to nickel-cobalt sulfide. Nickel-cobalt sulfide showed an overpotential of 282 mV while nickel-cobalt oxide displayed an overpotential of 379 mV to generate a current of 10 mA/cm ² , towards oxygen evolution. After introduction of 0.33 M urea, the potential for oxidation of urea for both nickel-cobalt oxide and nickel-cobalt sulfide is decreased to 1.34 V.
