Catalytic Oxidation Of Methanol Research Articles

In situ low-energy electron microscopy of chemical waves on a composite V-oxide/Rh(110) surface.

Chemical wave patterns and V-oxide redistribution in catalytic methanol oxidation on a VOx/Rh(110) surface have been investigated in the 10-4 mbar range with low-energy electron microscopy (LEEM) and micro spot low-energy electron diffraction (micro-LEED) as in situ methods. V coverages of θV = 0.2 and 0.4 MLE (monolayer equivalents) were studied. Pulses display a c(2⨯2) pattern in the reduced part and (1⨯2) and c(2⨯8) structures in the oxidized part of the surface. At θV = 0.4 MLE (1⨯2) / (1⨯4) patterns with streaks along the [001] direction at the 1/8 positions are present on the oxidized part of the surface. This phase can be assigned to V-oxide. Annealing the surface to 990 K under reaction conditions results in a macroscopic hole pattern in which holes of low VOx coverage are surrounded by a V-oxide layer. Chemical waves propagate inside the holes as well as on the VOx covered parts of the surface.

Activation energy of heterogeneous catalytic oxidation of methanol in oscillatory regime

Activation energy of heterogeneous catalytic oxidation of methanol in oscillatory regime

Synergistic photothermal catalytic oxidation of methanol and toluene mixture over Co-MOFs-derived catalyst: Interfacial and promotion effects

Herein, a series of Co/CoOx@CN nanocomposites with tunable synergistic interfacial structure were successfully obtained by a facile pyrolysis treatment. Among these nanocomposites, the nanocomposite pyrolyzed at 500 °C (denoted as Co/CoOx@CN-500) exhibited the best methanol photothermal catalytic activity (97% methanol conversion and 96% CO2 yield) under simulated solar irradiation. Compared with Co nanoparticles and Co@CN, Co/CoOx@CN-500 showed higher methanol photothermal catalytic activity. Moreover, the Co/CoOx@CN-500 also displayed a good ability to degrade methanol under outdoor natural solar. Such excellent photothermal activity mainly benefited from the strong interaction between the metals Co, CoOx and graphitic-carbon, which enhanced the photothermal effect by inducing the high work temperature, and the surface adsorb oxygen species of Co/CoOx@CN-500. Besides, the promotion effect of methanol on toluene oxidation was observed over Co/CoOx@CN-500 for the photothermal catalytic oxidation of the methanol and toluene mixture relative to their individual component. Water molecules did not affect the promotion effect of methanol on the photothermal catalytic oxidation of toluene. Reaction mechanism studies showed that 2-methylbenzaldehyde, the key intermediate formed by the reaction of formaldehyde generated by methanol oxidation and toluene, is the main reason for the improvement of the oxidation activity of toluene.

Catalytic Oxidation of Methanol to Formaldehyde Catalyzed by Iron Complex with N3S3-type Tripodal Ligand.

A Fe3+ complex with N3S3-type tripod ligand, 1, reacts with O2 in CH3OH to generate formaldehyde, which has been studied structurally, spectroscopically, and electrochemically. Complex 1 crystallizes as an octahedral structure with crystallographic C3 symmetry around the metal, with Fe-N=2.2917(17) Å and Fe-S=2.3574(6) Å. UV-vis spectrum of 1 in CH3OH under Ar shows an intense band at 572 nm (ϵ 4,100 M-1cm-1), which shifts to 590 nm (ϵ 2,860 M-1cm-1) by the addition of O2, and a new peak appeared at 781 nm (ϵ 790 M-1cm-1). Such a spectral change is not observed in CH2Cl2. Cyclic voltammogram (CV) of 1 in CH2Cl2 under Ar gives reversible redox waves assigned to Fe2+/Fe3+ and Fe3+/Fe4+ couples at -1.60 V (ΔE=69 mV) and -0.53 V (ΔE=71 mV) vs Fc/Fc+, respectively. In contrast, in CH3OH, the reversible redox waves, albeit accompanied by a positive shift of the Fe2+/Fe3+ couple, are observed at -1.20 V (ΔE=85 mV) and -0.53 V (ΔE=64 mV) vs Fc/Fc+ under Ar. Interestingly, a catalytic current was observed for the CV of 1 in CH3OH in the presence of CH3ONa under Ar, when the sweep rate was slowed down.

Different methanol oxidation behaviors on defectively nanoporous hematite photoanode modified with platinum via photoreduction versus electrodeposition

The present study involved the fabrication of a novel photoanode which was comprised with porously hematite nanorods (Vo-α-Fe2O3 PNRs); the electrode was subsequently employed as a support for anchoring Pt and used as a catalyst for the methanol oxidation reaction (MOR). Depending upon Pt decorations (electrodeposition versus photoreduction), the proposed photoanodes towards MOR displayed notable disparities. The electrode after Pt decoration by photoreduction (Vo-α-Fe2O3 PNRs/PtPR) demonstrated a hysteresis pattern in the cyclic voltammetry which was a typically catalytic oxidation of methanol. In the forward scan, the density of peak current reached 2.46 mA/cm2 at 0.71 VRHE. In contrast, the electrode after Pt decoration by electrodeposition (Vo-α-Fe2O3 PNRs/PtED) showed a robust lift in photocurrent as the voltage was increased in the voltammogram, reaching 2.5 mA/cm2 at 0.7 VRHE. The product generated at the latter electrode was identified to be formaldehyde with an impressive Faradaic efficiency of 95%. This finding was innovative and attractive. The detailed characterizations and DFT calculation revealed that the platinum’s different valence state and the charge transfer resistance variation on the electrode were the main factors for their disparate catalytic functions. Those two factors were closely related to the different Pt decoration methods. The disparate catalytic functions and their associated reaction mechanisms were proposed in this work.

Copper selenide - Porous carbon derived from metal-organic frameworks as an efficient electrocatalyst for methanol oxidation

In the present study, a metal-organic framework (Cu-MOF) was used as the precursor for synthesis of carbon-encapsulated copper selenides (namely, Cu2-xSe@PCs). After carbonization of Cu-MOF to Cu/Cu2O@PCs, the selenidation process was applied by selenium powder at 500 °C to form Cu2-xSe@PCs. Scanning electron microscopy showed the maintenance of the initial octahedral structure of Cu-MOF after carbonization and selenidation. Nickel foam (NF) was modified with the prepared composite and used as anode in electrochemical cells. Cyclic voltammetric study in alkaline solution (in the absence of methanol) showed highly increased peak currents (∼4 times) on Cu2-xSe@PCs/NF compared to that on Cu/Cu2O@PCs/NF. The electrocatalytic oxidation of methanol in alkaline solution showed lower overpotential and much higher catalytic currents (629.3 mA cm−2 in methanol 0.5 M) on Cu2-xSe@PCs/NF compared to that on Cu/Cu2O@PCs/NF (204.6 mA cm−2). The long-term stability of the proposed electrocatalyst was studied by chronopotentiometry and chronoamperometry. High potential stability was observed when a constant current (22.3 mA cm−2) was drawn from the cell (>4 h). Similar stability was observed for the catalytic current when a constant voltage (1.62 V vs. RHE) was imposed on the electrode in chronoamperometry. In addition, more than 88.5 % of the catalytic current remained after the application of 300 consecutive potential cycles to Cu2-xSe@ PCs/NF in the alkaline solution of methanol. The electrocatalyst was also used in a two-electrode system. Polarization and power density plots showed improved catalytic methanol oxidation by using Cu2-xSe@PCs/NF compared to Cu/Cu2O@PCs/NF. Excellent electrocatalytic properties of the proposed composite towards methanol, long-term stability and the simple synthetic route of the mono-metal electrocatalyst make it a good candidate as the anode of direct methanol fuel cells.

Stepwise Preparation of Uniform-Size Ultrafine Pt Nanoparticles for High-Performance Catalysis of Methanol Oxidation and Nitrophenol Reduction

Stepwise Preparation of Uniform-Size Ultrafine Pt Nanoparticles for High-Performance Catalysis of Methanol Oxidation and Nitrophenol Reduction

Regulating the surface local environment of MnO2 materials via metal-support interaction in Pt/MnO2 hetero-catalysts for boosting methanol oxidation

Rational use of the strong metal-support interaction (SMSI) is an important way to achieve the complete destruction of volatile organic compounds (VOCs). In order to investigate the influence of SMSI on the catalytic oxidation of VOCs, three Pt/MnO2 hetero-catalysts, i.e., Pt/α-MnO2, Pt/γ-MnO2 and Pt/δ-MnO2, were synthesized and then applied to the catalytic oxidation of methanol. The results showed that, compared with their corresponding pure MnO2, the temperatures (T90) at which 90% of methanol is converted to CO2 for the above three synthesized catalysts were reduced by 54 °C, 67 °C and 32 °C, respectively. The Pt/α-MnO2 catalyst has the best reducibility at lower temperature (T90 = 91 °C). Multiple characterization analyses confirm that the interaction between Pt and MnO2 support can increase the amount of Mn4+ and surface lattice oxygen on the catalyst surface. Thanks to the optimization of local reaction environment on the catalyst surface, Pt/MnO2 hetero-catalysts have better low temperature reduction capacity and stronger VOC deep oxidation capacity than corresponding pure MnO2 catalysts.

Prussian-blue-analogue derived FeNi2S4/NiS nanoframes supported by N-doped graphene for highly efficient methanol oxidation electrocatalysis

The design of effective and robust non-noble metal electrocatalysts to enhance catalytic reaction kinetic is critical to promote methanol oxidation catalysis. Herein, hierarchical Prussian blue analogue (PBA)-derived sulfide heterostructures supported by N-doped graphene (FeNi2S4/NiS-NG) as efficient catalysts have been developed for methanol oxidation reaction (MOR). Benefiting from the merits of hollow nanoframes structure and heterogeneous sulfide synergy, FeNi2S4/NiS-NG composite not only possesses abundant active sites to boost the catalytic properties but also alleviates the CO poisoning effect during the process exhibiting favorable kinetic behavior toward MOR. Specifically, the remarkable catalytic activity (97.6 mA cm−2/1544.3 mA mg−1) of FeNi2S4/NiS-NG for methanol oxidation was achieved, superior to most reported non-noble electrocatalysts. Additionally, the catalyst showed competitive electrocatalytic stability, with a current density of over 90% after 2000 consecutive CV cycles. This study offers promising insights into the rational modulation of the morphology and components of precious-metal-free catalysts for fuel cell applications.

Electrochemical Properties and Perspectives of Nickel(II) and Cobalt(II) Coordination Polymers-Aspects and an Application in Electrocatalytic Oxidation of Methanol

The electrochemical sensing potential of two isostructural one-dimensional nickel(II) and cobalt(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy) and 6-oxonicotinate (6-Onic), namely, {[Ni(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n and {[Co(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n, was investigated along with the polymers’ potential applications in the catalytic oxidation of methanol. The highly oxidative species from redox pairs Ni(II)/Ni(III) and Co(II)/Co(III) in these compounds represent catalytically active centres for oxidation of small molecules. A glassy carbon electrode (GCE) modified with a Ni polymer showed stability and reproducibility in 0.1 M NaOH, while the oxidation current inc 2reased with the increasing methanol concentration, suggesting that the Ni-polymer-modified electrode possess good sensing ability with respect to methanol. The GC electrode modified with the Co polymer is not reproducible and cannot be used for electroanalytical purposes under these experimental conditions. The GC electrode modified with the Ni polymer was successfully applied in the determination of methanol. This method showed favourable linear concentration dependence with a good sensitivity of 2.65 and 11.0 mA mM−1, a wide concentration range (0.001–4 mM), and a detection limit of 0.8 μM, which indicates its excellent application potential for methanol oxidation and thus its determination.

Unraveling the role of Co3O4 facet for photothermal catalytic oxidation of methanol via operando spectroscopy and theoretical investigation

Tubular, pie- and bread-shaped forms of Co3O4 with exposed {110}, {112} and {111} facets were prepared and compared in their photothermal catalytic performance and reaction pathways during the oxidation of methanol. Among them, the Co3O4 with exposed {110} facet exhibited the best photothermal catalytic performance (95% methanol conversion, 93% CO2 yield) under solar irradiation, while also maintaining good stability and moisture resistance. Reaction mechanism studies showed that the {110} facets had a strong adsorption capacity for formaldehyde, which facilitated its conversion to formate. The transformation of formaldehyde to formate species was the key step. The key step on the {110} facet was conversion of formaldehyde to a mono-dentate formate species, while conversion on the {112} and {111} facets was mainly to bi-dentate formate species. This study demonstrated that the design of preferential exposed crystal facet can regulate the pathway of photothermal catalytic reaction and realize efficient solar energy utilization.

Green preparation of self-supporting platinum nanoflower catalyst and its electrocatalytic oxidation performance of methanol

The three-dimensional (3D) self-supporting Pt nanoflower catalyst was prepared by using Pt organic compounds as precursors in a low-temperature molten salt system. The obtained Pt nanoflower nanoparticle can reach 400–500 nm with a face-centered cubic structure, which has the structural characteristics of a loose framework and more exposed active sites. The surfactant-free Pt nanoflower was directly used as methanol electrooxidation reaction (MOR) electrocatalysts without any pretreatment and activated carbon support. The results of electrochemical catalytic oxidation of methanol showed that the Pt nanoflower catalyst exhibit more enhanced electrocatalytic oxidation performance toward methanol compared with the commercial platinum black catalyst. The green and effective method can be developed and expected to enable mass production of fuel cell catalysts.

PdMo supported by graphene for synergistic boosting electrochemical catalysis of methanol oxidation

PdMo supported by graphene for synergistic boosting electrochemical catalysis of methanol oxidation

A NixCu100-x/NiOOH synergetic Pd complex for durable methanol oxidation electrocatalysis

Pd-based electrocatalysts play a crucial role in catalyzing methanol oxidation reaction (MOR) on the anode of direct methanol fuel cells due to their relative abundance (vs Pt) and novel activity. Unfortunately, the repaid activity loss seriously limits the practical application of these catalysts. Here, we report Pd-NixCu100-x/NiOOH synergy materials (PNCH-x) as a possible solution to this repaid activity loss issue. The oxygen evolution reaction performance of NixCu100-x/NiOOH counterparts is believed to play a decisive role in MOR durability enhancement and the reactivation feature of devitalized-Pd. As a result, the PNCH-83 presents an adaptive and activatable feature towards methanol oxidation, which shows an exhibited novel activity of 1565 A/g Pd, durability ∼ 200,000 s as well as exceptional periodic durability of ∼ 540,000 s. We anticipate that these findings and our methodology will help in understanding the synergistic effect and represent an important step forward in boosting MOR durability.

Synthesis of intermetallic FePtPd nanoparticles and their enhanced catalysis for electro-oxidation of methanol

Searching for efficient and CO-tolerant catalysts for electro-oxidation of methanol is desirable for the development of direct-methanol fuel cells. Here, we present a novel and facile procedure for the synthesis of intermetallic face-centered tetragonal (fct)-Fe50PtxPd50-x Nanoparticles (NPs) with Fe and Pt/Pd atoms forming alternative layers, which are highly active and stable in catalyzing methanol oxidation reaction (MOR) in 0.1 M HClO4 and 0.2 M methanol aqueous solution. The carbon-supported fct-Fe48Pt35Pd17 NPs show the highest peak current density of 626 A g−1Pt at 909 mV (vs RHE) over fcc-Fe48Pt35Pd17 (428 Ag−1Pt at 930 mV) and the commercial Pt (218 Ag−1Pt at 952 mV). The superior performance observed on the fct-Fe48Pt35Pd17 NPs is attributed to the stabilization of Pd by the intermetallic fct-structure, which improves the Pt CO-tolerance and catalytic activity. The activity of fct-FePtPd depends further on the Pt/Pd ratios. An increase in Pd content improves CO tolerance but reduces the number of active Pt sites on NPs surface, and the optimized Pt/Pd ratio should be around 1.0. Our work demonstrates a new approach to the rational design and synthesis of highly active NP catalysts for MOR.

Soft nanobrush-directed multifunctional MOF nanoarrays

Controlled growth of well-oriented metal-organic framework nanoarrays on requisite surfaces is of prominent significance for a broad range of applications such as catalysis, sensing, optics and electronics. Herein, we develop a highly flexible soft nanobrush-directed synthesis approach for precise in situ fabrication of MOF nanoarrays on diverse substrates. The soft nanobrushes are constructed via surface-initiated living crystallization-driven self-assembly and their active poly(2-vinylpyridine) corona captures abundant metal cations through coordination interactions. This allows the rapid heterogeneous growth of MOF nanoparticles and the subsequent formation of MIL-100 (Fe), HKUST-1 and CUT-8 (Cu) nanoarrays with tailored heights of 220~1100 nm on silicon wafer, Ni foam and ceramic tube. Auxiliary functional components including metal oxygen clusters and precious metal nanoparticles can be readily incorporated to finely fabricate hybrid structures with synergistic features. Remarkably, the MIL-100 (Fe) nanoarrays doped with Keggin H3PMo10V2O40 dramatically boost formaldehyde selectivity up to 92.8% in catalytic oxidation of methanol. Moreover, the HKUST-1 nanoarrays decorated with Pt nanoparticles show exceptional sensitivity to H2S with a ppb-level detection limit.

Low-Temperature Catalytic Ozonation of Multitype VOCs over Zeolite-Supported Catalysts.

Volatile organic compounds (VOCs) are an important source of air pollution, harmful to human health and the environment, and important precursors of secondary organic aerosols, O3 and photochemical smog. This study focused on the low-temperature catalytic oxidation and degradation of benzene, dichloroethane, methanethiol, methanol and methylamine by ozone. Benzene was used as a model compound, and a molecular sieve was selected as a catalyst carrier to prepare a series of supported active metal catalysts by impregnation. The effects of ozone on the catalytic oxidation of VOCs and catalysts' activity were studied. Taking benzene as a model compound, low-temperature ozone catalytic oxidation was conducted to explore the influence of the catalyst carrier, the active metal and the precious metal Pt on the catalytic degradation of benzene. The optimal catalyst appeared to be 0.75%Pt-10%Fe/HZSM(200). The catalytic activity and formation of the by-products methylamine, methanethiol, methanol, dichloroethane and benzene over 0.75%Pt-10%Fe/HZSM(200) were investigated. The structure, oxygen vacancy, surface properties and surface acidity of the catalysts were investigated. XRD, TEM, XPS, H2-TPR, EPR, CO2-TPD, BET, C6H6-TPD and Py-IR were combined to establish the correlation between the surface properties of the catalysts and the degradation activity.

Effect of the Potentiostatic and Potentiodynamic Dealloying on the Structure and Chemical Distribution of Ag Atoms in Au-Enriched Nanoparticles

Recently, nanoporous gold (np-Au) prepared by dealloying has emerged as an efficient and durable catalyst for electrochemical oxidation of small alcohols. [1] An additional increase of surface-to-volume ratio by nano-sizing of AuxAg1-x master alloy might improve the catalytic methanol oxidation reaction (MOR). Only few research groups have recently shown that the morphology, structure and elemental distribution of dealloyed nanoparticles (NPs) depend on the various parameters such as initial particle size and composition.[2-4] Starting from AuxAg1-x alloy NPs, it is, however, unclear how the different dealloyed Au-rich NP motifs such as core-shell, hollow or porous NPs and the Ag distribution influence the catalytic MOR performance.In this work, we have investigated the effects of potentiodynamic and potentiostatic dealloying methods on the structure and chemical distribution of the residual Ag atoms for dealloyed Au-rich NPs. First, two size types of Ag-rich AuxAg1-x alloy NPs were prepared by one pot colloidal route and wet impregnation route. Larger Au23Ag77 NPs (size of 77 ± 26 nm) form a homogeneous disordered alloy, while the Au14Ag86 NPs with a size of 12 ± 5 nm show a strong enrichment of Ag atoms at the particle surface, referred to as core-shell arrangement. Subsequently, the as-prepared NPs with two sizes (12 nm and 77 nm) were electrochemically dealloyed using a potentiodynamic (cyclic voltammetry, CV) or potentiostatic (chronoamperometry, CA) method in 0.1 M HClO4. We observed that the CV method leads to the formation of pores inside the initial 77 nm NPs. Very interestingly, high-resolution STEM-EDX shows the appearance of Ag-rich regions near to the pore network of these dealloyed NPs. Unlike, after the dealloying by CV method the initial 12 nm NPs are still dense and solid, forming a thin Au-rich particle shell. After the exposure to air, the internal Ag atoms tend to segregate to the particle surface. In the CA method, we pointed out that the applied anodic potential has a strong influence of the surface diffusion behavior of the remaining Au atoms. Below a critical potential of 1.3 V vs. RHE, the dealloying process is kinetically hindered by the passivation of Au surface atoms. This critical potential in the CA method is strongly different to the critical dissolution potential of Ag atoms for AgxAu1-x NPs obtained from the CV profile (around 1.05 V vs. RHE). However, when the applied potential is larger than the critical potential, e.g. 1.6 V vs. RHE, the difference in the obtained structure and composition of dealloyed 77 nm NPs is negligible between potentiodynamic and potentiostatic approaches. On the other hand, the potentiostatic dealloying at 1.6 V vs. RHE leads to higher surface content of residual Ag for dealloyed NPs with 12 nm compared to potentiodynamic. This increased enrichment of the residual Ag atoms near the particle surface is also supported by XPS.In summary, we correlate the structural parameters (initial particle size, composition/distribution) of dealloyed AgxAu1-x NPs with the electrochemical dealloying methods (potentiostatic vs. potentiodynamic). Tailoring the surface diffusion rate of the Au atoms and the Ag distribution helps to improve the catalytic performance for MOR.

Challenges and Prospects in the Catalytic Conversion of Carbon Dioxide to Formaldehyde

AbstractFormaldehyde (HCHO) is a crucial C1 building block for daily‐life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy‐ and cost‐intensive gas‐phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2‐to‐HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed.

Challenges and Prospects in the Catalytic Conversion of Carbon Dioxide to Formaldehyde.

Formaldehyde (HCHO) is a crucial C1 building block for daily-life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy- and cost-intensive gas-phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2 ) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2 -to-HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed.