Methanol Decomposition Research Articles

Activated carbon from waste biomass as catalyst support: formation of active phase in copper and cobalt catalysts for methanol decomposition

Activated carbons (AC) from various waste agriculture precursors with different texture and surface characteristics were obtained by different preparation procedures. These AC were used as a host matrix of mono- and bi-component copper and cobalt nanoparticles. The effect of carbon properties on the formation of copper/cobalt phases was studied by Boehm method, XRD, nitrogen physisorption, UV–Vis, FTIR, TPR–TG analysis and methanol decomposition as a catalytic test. The elucidation of activated carbons from waste biomass as catalyst support was based on the comparative study with similar materials supported on mesoporous silica KIT-6. It was demonstrated that contrary to KIT-6, the reduction properties of AC support hinders the formation of spinel CuCo2O4 phase in the bi-component materials, but provides formation of mixture of finely dispersed and highly active and selective in methanol decomposition Cu2O and CoO nanoparticles.

Activated carbons from waste biomass and low rank coals as catalyst supports for hydrogen production by methanol decomposition

Activated carbons with different textural and chemical surface characteristics were synthesized from waste biomass and low rank coals, and furthermore used as a host matrix for cobalt species, varying the preparation and modification methods. The obtained activated carbons and modified samples were characterized by complex of various physicochemical methods, such as: low temperature physisorption of nitrogen, XRD, EPR, XPS, UV–Vis and TPR with hydrogen. Boehm method was applied for qualitative and quantitative determination of oxygen-containing groups on the carbon surface before and after cobalt deposition. The catalytic properties of cobalt modifications were tested in methanol decomposition. The dominant effect of activated carbon texture over the surface chemistry on the state and catalytic behavior of cobalt species was discussed.

(Invited) A Kinetics Analysis of Methanol Oxidation Under Electrolysis/Fuel Cell Working Conditions

Instead of using a DMFC hardware as an elementary Direct Methanol Fuel Cell, it is possible to use it as an electrolyzer to produce clean hydrogen at the Pt/C electrode negatively polarized by applying a positive electrode potential at the Pt-Ru anode. In this way the DMFC hardware works as an elementary electrolysis cell with hydrogen generation at the Pt/C cathode by electro-reduction of the protons coming from methanol oxidation at the Pt-Ru anode and crossing over the protonic membrane. The elementary electrochemical reactions involved are: CH3OH + H2O → CO2 + 6 H+ + 6 e- anode reaction (1) 6 H+ + 6 e- → 3 H2 cathode reaction (2) ____________________________________ CH3OH + H2O → CO2 + 3 H2 overall reaction (3) with the thermodynamic data ΔHo = + 131.5 kJ/mole and ΔGo = + 9.3 kJ/mole for the overall reaction (3). Thus the minimum energy needed to generate one mole of hydrogen is equal to ΔHo/3 ≈ + 44 kJ/mole, which is much lower than that used in water electrolysis (ΔHo = + 286 kJ/mole under standard conditions). Moreover the anode potential is Ea + = + ΔGo/6F » 0.016 V/SHE and the cell voltage under standard conditions is Uo cell = Ea + - Ec- ≈ 0.016 V where Ec- = 0 V is the cathode potential vs. the Standard Hydrogen Electrode (SHE). Thus the electrochemical decomposition of methanol according to reaction (3), using a Proton Exchange Membrane Electrolysis Cell (PEMEC), is a more convenient and efficient process [1-2] to produce high-purity hydrogen than water electrolysis [3], since the theoretical cell voltage under standard conditions is much lower (Uo cell = 0.016 V) than that of water decomposition (Uo cell= 1.23 V). The DMFC hardware, provided by ElectroChem (ref.: EFC-05-02-DM), consists of a Pt/C electrode and a Pt-Ru (1/1)/C electrode of 5 cm2 surface area separated by a Nafion®117 membrane. The cell was polarized at a constant current density, j (from 1 to 100 mA cm-2), using a potentiostat and the methanol anode potential was deduced from the cell voltage since the hydrogen evolution cathode can be used as a hydrogen reference electrode. In that way it was possible to obtain the methanol oxidation electric characteristics Emeth= f(j) at several methanol concentrations (from 0.1 M to 10 M) and several working temperatures (from 25°C to 85°C). These methanol oxidation characteristics, corrected from ohmic losses due to membrane and interface resistances, were then analysed leading to the transfer coefficient, α, the reaction order vs. methanol, p, and the heat of activation, ΔH*. The results obtained (α ≈ 0.5 to 0.6, p ≈ 0.3 and ΔH* ≈ 50 to 60 kJ/mole) are in good agreement with those obtained in a 3-electrode electrochemical cell [4-7].

Concerning the Role of Sacrificial Reagents in Photocatalytic Water Splitting Systems: A Critical Assessment

One of the most important limitations for the application of photocatalytic techniques for water decomposition is that the process employing pure water is usually found to be rather inefficient. This is generally related to the fact that the simultaneous reduction and oxidation of water is a complex multistep reaction involving (at least!) four electrons. Using sacrificial molecules as electron donors can remarkably improve the H2 production with the holes being scavenged by these molecules thus reducing the charge carrier recombination significantly. Furthermore, as O2 is not produced, the back reaction to produce water is suppressed, increasing the H2 yield and avoiding a subsequent gas separation stage. However, it should be noted here that the yield of the H2 formation will eventually be reduced by competing reduction reactions with the products formed upon the oxidation of the sacrificial reagents. Organic compounds such as alcohols, organic acids, and hydrocarbons can act as efficient hole scavengers (i.e., as electron donors) for the photocatalytic H2 generation. In particular, methanol is frequently used as sacrificial reagent. For practical applications, the utilization of methanol will only be environmentally sensible provided that it is derived from biomass or from toxic residues that must be disposed of. Adding methanol as electron donor to react irreversibly with the photo-generated holes can enhance the photocatalytic electron/hole separation efficiency resulting in higher quantum yields. Since electron donors are consumed in the photocatalytic reaction, their continuous addition is required to sustain H2 production. A sequential oxidation mechanism has been proposed for the overall methanol decomposition resulting in a lower energy that can be stored as compared with the cyclic splitting of water. While the first two reactions have a positive Gibbs free energy and are thus thermodynamically unfavorable at room temperature, the third reaction has a large negative Gibbs energy, thus it intrinsically provides a barrier for the undesired reverse consumption of the generated H2 gas. Two possible mechanisms are proposed for photocatalytic oxidation of methanol: (1) the direct oxidation by photogenerated holes and (2) the indirect oxidation via interfacial by formed •OH radicals that are products of trapping valence band holes by surface −OH groups or adsorbed water molecules. It is still a challenge to distinguish between the two mechanisms in practice due to the lack of suitable probe techniques. While the choice of sacrificial electron donors for studies concerning the photocatalytic formation of molecular H2 appears to be rather large, the sacrificial photocatalytic oxidation of water is only reported for a rather limited variety of electron acceptors. By far the vast majority of the research groups working on this topic employs silver cations, Ag+, as electron acceptors with the involved reactions being proposed just suggest that silver cations act solely as electron acceptors. Hence, the photocatalytic formation of molecular oxygen is accompanied by the deposition of metallic silver nano-contacts on the semiconductor’s surface. Obviously, this will lead to irreversible optical changes of these systems due to the plasmonic absorption band of the silver nanoparticles in the visible spectral region. Moreover, noble metal nanoparticles are known for their catalytic activity resulting most likely in changes in the chemical and photochemical properties of these systems. It is interesting to note that these rather drastic changes are hardly ever discussed in the respective literature nor is any experimental work conducted to ensure that the photocatalytic properties remain unchanged upon the formation of the silver particles. Even though no exact count exists here, it seems fair to say that Ag+ is employed in at least 95 % of the published papers dealing with the sacrificial photocatalytic water oxidation. However, no O2 is formed once electron acceptors such as carbon tetrachloride or tetranitromethane are used even though their irreversible one-electron reduction is readily observed. To explain these at first sight contradictory results it is suggested here that the role of suitable sacrificial electron acceptors such as (and also ) is highly underestimated. In particular, their possible involvement in the actual water oxidation mechanism has so far not been discussed at all. We are convinced that it is most certainly highly indicated to study the role of such metal cations in the photocatalytic water oxidation in detail. Their catalytic role is proposed here for the first time, however, it could be part of a much more general mechanism thus opening up new design features for photocatalytic and photoelectrochemical energy-to-fuel conversion systems. Reference: J. Schneider, D. W. Bahnemann, “Undesired Role of Sacrificial Reagents in Photocatalysis”, J. Phys. Chem. Letters 4 (2013) 3479-3483

Performance of a combined cooling heating and power system with mid-and-low temperature solar thermal energy and methanol decomposition integration

In this paper, a new distributed energy system that integrates the mid-and-low temperature solar energy thermochemical process and the methanol decomposition is proposed. Through the solar energy receiver/reactor, the energy collected by a parabolic trough concentrator, at 200–300°C, is used to drive the decomposition reaction of the methanol into the synthesis gas, and thus the solar thermal energy is converted to the chemical energy. The chemical energy of the synthesis gas released in the combustion chamber of a micro gas turbine is used to drive the combined cooling heating and power systems. Energy analysis and exergy analysis of the system are implemented to evaluate the feasibility of the proposed system. Under the considerations of the changes of the solar irradiation intensity, the off-design performances of the micro turbine and the variations of the load, the design and off-design thermodynamic performances of the system and the characteristics of the chemical energy storage are numerically studied. Numerical results indicate that the primary energy ratio of the system is 76.40%, and the net solar-electricity conversion rate reaches 22.56%, which is higher than exiting large-scale solar thermal power plants. Owing to the introduction of a the solar thermochemical energy storage in the proposed system, the power generation efficiency is insensitive to the variations of the solar radiation, and thus an efficient and stable utilization approach of the solar thermal energy is achieved at all work condition.

Kinetics Analysis of the Electrocatalytic Oxidation of Methanol inside a DMFC working as a PEM Electrolysis Cell (PEMEC) to generate Clean Hydrogen

The electrochemical decomposition of methanol for hydrogen production has been carried out at several temperatures (25 to 85°C) and different methanol concentrations (0.1 to 10M in 0.5M H2SO4) using a DMFC hardware working as a Proton Exchange Membrane Electrolysis Cell (PEMEC). Conversely to most of recent studies which investigated the effect of working parameters (cell voltage, methanol concentration, flow rate of reactants, temperature, etc.) on the hydrogen evolution rate, this work is focussed on the analysis of the kinetics of methanol oxidation at the anode using the hydrogen cathode as a reference electrode. In this way it was possible to plot the cell voltage (corrected from the ohmic drop) as a function of the logarithm of the imposed current density. A Tafel analysis of these plots allowed us to estimate the kinetics parameters of methanol oxidation, i.e. the charge transfer coefficient α of the rate determining step and the heat of activation Δ of the overall process. The values obtained for these parameters (α≈ 0.5 to 0.6, Δ̑H̆*≈50–60kJmol−1) are similar to those published in the literature as deduced from the analysis of methanol oxidation both on smooth Pt-Ru electrodes and on Pt-Ru nanoparticles supported on carbon powders.

Single-phase Ni3Sn alloy alkali-leached for hydrogen production from methanol decomposition

Methanol decomposition over alkali-leached Ni3Sn powder at 513–793 K was investigated. Compared with untreated Ni3Sn, alkali-leached Ni3Sn had high catalytic activity and selectivity toward H2 and CO production above 633 K. A maximum H2 production rate of 100 × 10−3 mol h−1 g-Cat−1 and H2 selectivity above 95% were attained over alkali-leached Ni3Sn at 793 K. Alkali-leached Ni3Sn presented good catalytic activity for 45 h of reaction at 713 K, whereas Ni3Sn had none. The activation energy was calculated, and its values rapidly decreased from Ni3Sn to alkali-leached ones. The improvement was attributed to the formation of Ni nanoparticles less than 100 nm in diameter in the alkali-leaching process, which had high activity for methanol decomposition. The improved catalytic activity favored the gradual formation of fine Ni3Sn particle during the reaction, which served as the active sites for methanol decomposition when the catalytic activity decreased because of carbon deposition on the Ni surface. Results demonstrated that alkali-leached Ni3Sn was a promising potential catalyst for hydrogen production from methanol.

Density Functional Theory Comparison of Methanol Decomposition and Reverse Reactions on Metal Surfaces

Methanol decomposition on metals has been subject of several theoretical studies, usually concentrating on a particular set of reactions in the main reaction path. In this work, we present an extensive study that considers all potential elementary steps for four close-packed surfaces including Cu, Ru, Pt, and Pd that shows the different behaviors and alternative routes through which the decomposition can take place by theoretical methods, including dispersion contributions. Decomposition follows different paths on these metals; while Cu would produce CH2O, CO is the major product for the other metals. In addition, coverage effects might change the first step in Pt and Ru from methylenic to alcohol H activation. Alternatively the reaction network can be inspected for the formation of methanol from CO and hydrogen. Under these conditions, Cu generates CH2O and only at very high H coverages is methanol likely to appear. On Pd, methanol formation and CHOH dissociation compete, thus leading to an inefficient process. A similar path takes place for Pt. For Ru the lateral paths leading to C–O breaking can occur at several points in the reaction network, never reaching CH3OH. A compilation of the results with comparable computational setups presents a detailed database that can be added to the thermodynamics and kinetics for other reactions, such as methanation, with which they share a common list of reactions, or employed when analyzing larger alcohols such as those derived from biomass.

A CFD Simulation of Hydrogen Production in Microreactors

In this study, the modeling of hydrogen production process in microreactors by methanol-steam reforming reaction is investigated. The catalytic reaction of methanol-steam reforming producing hydrogen is simulated considering a 3D geometry for the microreactor. To calculate diffusion among species, mixture average correlations are compared to Stephan-Maxwell equations. The reactions occurring inside the microreactor include reforming of methanol with steam, methanol decomposition, and a reaction between carbon dioxide and hydrogen. The main objectives of this study are the prediction of temperature profile along the microreactor using either mixture average method or Stephan-Maxwell one and the comparison between the present predictions and some existing experimental data. The simulation results indicate that Stephan-Maxwell method conforms more suitably to the experimental results. The difference is more at lower feed flow rates since, when the flow rate increases, mass transfer mechanism changes from diffusion to convection, which in turn reduces the difference.

A cuboctahedral platinum (Pt79) nanocluster enclosed by well defined facets favours di-sigma adsorption and improves the reaction kinetics for methanol fuel cells.

The methanol dehydrogenation steps are studied very systematically on the (111) facet of a cuboctahedral platinum (Pt79) nanocluster enclosed by well-defined facets. The various intermediates formed during the methanol decompositions are adsorbed at the edge and bridge site of the facet either vertically (through C- and O-centres) or in parallel. The di-sigma adsorption (in parallel) on the (111) facet of the nanocluster is the most stable structure for most of the intermediates and such binding improves the interaction between the substrate and the nanocluster and thus the catalytic activity. The reaction thermodynamics, activation barrier, and temperature dependent reaction rates are calculated for all the successive methanol dehydrogenation steps to understand the methanol decomposition mechanism, and these values are compared with previous studies to understand the catalytic activity of the nanocluster. We find the catalytic activity of the nanocluster is excellent while comparing with any previous reports and the methanol dehydrogenation thermodynamics and kinetics are best when the intermediates are adsorbed in a di-sigma manner.

Co-modified Pd/CeO2-ZrO2 catalysts for methanol decomposition

Pd/Ce0.8Zr0.2O2 catalysts modified by cobalt were prepared by a sequential impregnation method and characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption (Brunauer-Emmet-Teller), oxygen storage capacity (OSC), CO-chemisorption, H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The effect of Co on the performance of methanol decomposition was evaluated at a fixed-bed microreactor. The results showed that the addition of Co can improve the oxygen storage capacity of the catalyst and the dispersion of Pd. XPS results indicated that Pd was in a partly oxidized (Pdδ+, 1<δ<2) state and Co2+ was present in Pd catalysts modified by Co. A 90% conversion of methanol was achieved at around 280 °C over Pd-Co/Ce0.8Zr0.2O2 catalyst which was 20 °C lower than that over Pd/Ce0.8Zr0.2O2, indicating that both Pdδ+and Co2+ play an important role in improving the catalytic activity of methanol decomposition.

Nanostructured copper-zirconia composites as catalysts for methanol decomposition

Nanostructured mesoporous ZrO2 was obtained by hydrothermal synthesis using surfactant assisted approach. Copper modifications of thus obtained ZrO2 (4–25wt.% copper) were prepared by incipient wetness impregnation with the corresponding nitrate or acetyl acetonate precursors and further treatment in oxidative or reduction atmosphere. The obtained materials were characterized by N2 physisorption, XRD, UV–vis, FTIR, XPS and temperature programmed reduction with hydrogen and tested as catalysts in methanol decomposition to hydrogen and CO. Selected samples were investigated after partial coverage of the surface with 11C-labeled methanol and 11C-labeled methyl formate. The formation of monolayer of finely dispersed copper oxide species on zirconia at about 4wt.% copper loading and bulk copper nanoparticles at higher one is observed. It was assumed that zirconia support provides the formation of two types of catalytic sites: the first ones strongly adsorb methanol and exhibit predominantly dehydrogenation activity, while the others, possess acidic function. The modification of zirconia with copper significantly improves the catalytic activity and selectivity in methanol decomposition via (i) creation of additional surface acidic sites which contribute to generation of methoxy intermediates; (ii) stabilization of Cu2+-Cu+ and Cu+-Cu0 redox pairs where the electron transfer is facilitated by zirconia support and (iii) assisting the recombination and release of hydrogen during the transformation of produced on zirconia surface intermediates.

Hydrogen production through methanol steam reforming: Effect of synthesis parameters on Ni–Cu/CaO–SiO2 catalysts activity

The objectives of this study were to prepare Ni–Cu/CaO–SiO2 catalysts by a modified polyol process with different preparation conditions and evaluate the feasibility of hydrogen production from methanol steam reforming. CaO–SiO2 materials possess high specific surface areas and CO2 absorption capacities which were synthesized through the sol–gel method to serve as supports. The experimental results of the methanol steam reforming indicated that the highest catalytic activity was achieved when the Ni–Cu/CaO–SiO2 catalyst was prepared under Ar atmosphere at a reduction temperature of 160 °C (160-Ar). The 160-Ar catalyst synthesized by this method has a large pore volume and a high mesoporosity. These physical properties contribute to the effective dispersion of metal particles in the 160-Ar catalyst. Increasing the MeOH/H2O ratio was found to promote the water–gas shift reaction and direct methanol decomposition to produce more H2.

Reactive Sputtering of Plasmonic Pt/ZnO Films for Decomposition of Gas-Phase Methanol under Visible Light.

The preparation of ZnO films by a versatile and effective facing-target sputtering method under various sputtering pressures is described. The ZnO films are coated with an ultrathin (2 nm) Pt layer through dc diode sputtering to form hybrid Pt/ZnO photocatalytic films. Interestingly, the Pt/ZnO films show an efficient visible-light photoresponse for the decomposition of gas-phase methanol owing to the unique surface plasmon resonance of the Pt film.

Hydrogen Production by Partial Oxidation of Methanol Over Gold Supported on Fe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;

Partial oxidation of methanol (POM) to produce hydrogen was investigated over Au/Fe2O3 catalysts. The catalysts were prepared by inverse co-precipitation method. The influence of catalyst synthesis parameters such as precipitant, gold loading, calcination temperature and reaction parameter such as reaction temperature on POM reaction to produce hydrogen were investigated. The catalysts have been characterized by means of TGA, BET, XRD, TEM, SEM-EDS and XPS analyses. TGA and DTGA profiles clearly indicate that minimum decomposition temperature required to obtain Fe2O3 in Au/Fe2O3 catalysts is 660 K. SEM-EDS analysis confirms that Au and Fe in Au/Fe2O3 are homogeneously distributed over the agglomerate. A detailed microstuctural characterization of Au/Fe2O3 sample by XRD, TEM and XPS analyses has shown that nanometer sized gold particles with oxidized gold species is in predominant amount in the uncalcined catalysts sample. The mean particle size and metallic state of gold particles increase with increasing calcination temperature. A highly active Au/Fe2O3 catalyst is obtained by using Na2CO3 as precipitant with lower gold loading and calcination at 673 K. The catalytic behavior of the Au/Fe2O3 catalyst is related not only to the gold but also to the chemical state of the support. The effect of reaction temperature on the catalytic performance of the Au/Fe2O3 catalysts was studied in the temperature range of 423 to 523 K. Oxygen conversion was complete through out the examined temperature range. Methanol conversion increased with rise in temperature and attains 100% at 503 K; Hydrogen selectivity increased with rise in reaction temperature up to 523 K and then dropped off. The overall reactions involved are methanol combustion, partial oxidation, steam reforming and decomposition. CO produced by methanol decomposition and/or by reverse water gas shift is subsequently transformed into CO2 and H2 by the water gas shift and/or CO oxidation.

Decomposition of methanol on ZnO(CeO2, La2O3)-CuO-NiO-based monoliths

An influence of nickel oxide as a component of ZnO(CeO2, La2O3)-CuO-NiO/Al2O3 based catalysts, supported by structured ceramic monoliths, on their operation in methanol decomposition is studied. The results obtained, including with use of XRD, SEM, TPR techniques, show that NiO-doping causes promoting effect achieving 90–96 % of hydrogen yield as a target product at moderate temperatures of 250–320 °C. We attribute this effect to a decreased reducibility of a copper oxide within the catalyst composition.

Control of copper particles deposition in mesoporous SBA-15 silica by modified CVD method

Copper supported SBA-15 catalysts were prepared by modified Organometallic Chemical Vapor Deposition (OMCVD) technique. The materials were characterized by nitrogen physisorption, XRD, TEM, UV–Vis, XPS and temperature programmed reduction. Catalytic reductions of NO with CO and with a mixture of CO and methane as well as methanol decomposition were used as catalytic tests. The modified OMCVD procedure favors the formation of very finely dispersed nanoparticles located deeply into the micropores and the small mesopores of the SBA-15 silica matrix, while larger and predominantly located on the external surface copper species are detected for the materials prepared by conventional wet impregnation procedure.

Catalytic Performance of Oxidized Ni3Sn2 for Hydrogen Production from Methanol Decomposition

The catalytic properties of oxidized Ni3Sn2 powders were investigated for producing hydrogen from decomposing methanol in the temperatures ranging from 240 to 480 ºC. The oxidized Ni3Sn2 had much higher catalytic activity than that of Ni3Sn2 in the temperature range of 320~400 ºC. The results of an isothermal test performed at 320 ºC revealed that the oxidized Ni3Sn2 was spontaneously activated within 4 h of the reaction and slowly deactivated in the followed reaction time. The oxidized Ni3Sn2 suppressed side reactions such as methanation and water-gas shift reaction and showed a high efficiency for H2 production from methanol decomposition. Surface analysis revealed that the activity of oxidized Ni3Sn2 was attributed to the formation of Ni/SnO2 catalyst, which was supposed to serve as active sites for methanol decomposition.

Synthesis of C2+ hydrocarbons by CO2 hydrogenation over the composite catalyst of Cu–Zn–Al oxide and HB zeolite using two-stage reactor system under low pressure

The combination of methanol synthesis and methanol-to-gasoline (MTG) reaction is a beneficial process to produce particular C2+ hydrocarbons from CO2 and H2, because MTG reaction can produce C2+ hydrocarbons selectively without the formation of methane. However, the composite catalysts consisting of methanol synthesis catalyst and zeolite previously reported have produced C2+ hydrocarbons in poor yields especially under low pressure conditions. This paper reports the high yield production of C2+ hydrocarbons by CO2 hydrogenation using a two-stage reaction system consisting of a Cu–Zn–Al oxide catalyst in the first reactor and a composite catalyst of the Cu–Zn–Al oxide and HB (zeolite beta) in the second reactor. The key points of this system are reversed water-gas-shift (RWGS) reaction in the first reactor and the following H2O removal before the second reactor. The gas mixture supplied to the second reactor containing much amount of CO and little H2O enhanced the methanol synthesis and suppressed the methanol decomposition to CO over the Cu–Zn–Al oxide catalyst in the composite catalyst, promoting the MTG reaction to produce C2+ hydrocarbons over HB zeolite. The highest yield of C2+ hydrocarbons reached to approximately 15C-mol% under 0.98MPa.

Catalytic performance of Ni–Al nanoparticles fabricated by arc plasma evaporation for methanol decomposition

The catalytic properties of Ni-25 at% Al (Ni25Al) nanoparticles fabricated by arc plasma evaporation toward methanol decomposition were studied at temperatures ranging from 513 to 753 K. The Ni25Al nanoparticles showed much higher activity than gas atomized Ni25Al powders. They showed a high degree of selectivity for methanol decomposition into H2 and CO. Side reactions such as methanation and water-gas shift reaction were suppressed to a high temperature of 673 K, which is hardly achieved for common Ni catalysts. Detailed characterization of the Ni25Al nanoparticles showed that they were composed of Ni, Ni3Al, and Al2O3 phases with Ni and Al oxides on the surface of the Ni and Ni3Al phases. The Ni oxides were reduced to Ni phase by a hydrogen reduction prior to methanol decomposition, while the Al oxides remained unchanged. It is supposed that the Ni phase provided the active sites for methanol decomposition, and the Ni3Al and Al2O3 phases acted as supports for the Ni phase. Probably the Ni3Al and Al2O3 phases provided good resistance to agglomeration of the Ni phase during the reaction, which might contribute to maintain the high catalytic performance of the nanoparticles for methanol decomposition.