Highlights• Catalytic hydrogen combustion was studied in a Pt washcoat on SiC foam• The catalyst contains Pt particles of 5-20 nm size on porous Al 2 O 3 with ceria additive • Kinetics was monitored by measuring water concentration through FTIR • The Pt/SiC material shows high thermal stability and reaction start-up at room temperature • Catalyst converted at least 18.5 L H2 .min -1 .g Pt -1 with 35kJ.mol -1 activation energy Abstract A commercial Pt based washcoat, used for catalytic methane combustion, was studied supported on a commercial SiC foam as catalytic material (Pt/SiC) for catalytic hydrogen combustion (CHC). Structural and chemical characterization was performed using Electron Microscopy, X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). The reaction was monitored following water concentration by Fourier Transform Infrared spectra (FTIR). The FTIR method was compared with H2 detection by Gas Cromatography (GC) and has shown to be adequate to study the kinetics of the CHC reaction in steady state under our experimental conditions (very lean 1% (v/v) H2/air mixtures). The catalyst is composed of 5-20 nm disperse Pt nanoparticles decorating a mixture of high surface area Al2O3 and small amounts of ceria supported on the SiC foam which also contains alumina as binder. The Pt/SiC catalytic material has demonstrated to be active enough to start up the reaction in a few seconds at room temperature. The material has been able to convert at least 18.5Lhydrogen.min -1 .gPt -1 at room temperature in conditions of excess of catalyst. The Pt/SiC material was studied after use using XPS and no significant changes on Pt oxidation states were found. The material was characterized from a kinetic point of view. From the conversion-temperature plot a T50 (temperature for 50% conversion) of 34 o C was obtained. Activation energy measured in our conditions was 35±1 kJ.mol -1 .

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We report the study of the catalytic hydrogen combustion over Pt-impregnated powdery silicon carbide (SiC) using H 2 PtCl 6 as precursor. The reaction was conducted in excess of oxygen. -SiC was selected for the study because of its thermal conductivity, mechanical properties, chemical inertness and surface area. The obtained Pt particles over SiC were medium size (average particle diameter of 5 nm for 0.5wt% Pt). The activity of the Pt-impregnated catalyst over SiC was compared to those obtained in oxidized form over TiO 2 and Al 2 O 3 commercial supports (Pt particles very small in size, average particle diameter of 1 nm for 0.5wt% Pt in both cases). The case of a SiO 2 support was also discussed. Those Pt/SiC particles were the most active because of their higher contribution of surface Pt 0 , indicating that partially oxidized surfaces have better activity than those totally oxidized in these conditions. SiC was modified with an acid treatment and thus bigger (average particle diameter of 7 nm for 0.5wt% Pt) and more active Pt particles were obtained. Durability of the SiC and TiO 2 supported catalysts was tested upon 5 cycles and both have shown to be durable and even more active than initially. Exposure to the oxidative reaction mixture activates the *Revised Manuscript Click here to view linked References catalysts and the effect is more pronounced for the completely oxidized particles. This is due to the surface oxygen chemisorption which activates catalysts´ surface.

In this work, we prepared SiC-supported Pt-Cu thin films by magnetron sputtering for use as catalysts for the combustion of hydrogen under oxidizing conditions. We tested the catalysts as prepared and after chemical dealloying. A methodology is presented to fabricate catalytic thin films of a desired composition with tailored magnetron targets with lower Pt consumption. The deposition gas was changed to prepare columnar (Ardeposited) and closed-porous (He-deposited) films to study the effect of the microstructure on the activity. The effect of composition was also studied for the columnar samples. The as-prepared Pt-Cu thin films showed significant activity only at temperatures higher than 100°C. Dealloying permitted an increase in the activity to achieve near room-temperature activity. The dealloyed closed-porous He-deposited sample was the most active, being able to convert as much as 13.15 LH2•min -1 •gPt -1 at 70°C (Ea=1kJ.mol -1 ). This sample was preferentially dealloyed on the surface, yielding Código de campo cambiado Código de campo cambiado Código de campo cambiadoan almost pure Pt shell (96% at. Pt) and a Cu-depleted interior (71% at. Pt). This compositional inhomogeneity enabled the sample to achieve enhanced activity compared to the Ar-deposited columnar sample (with similar initial composition, but uniformly dealloyed), probably due to the compressive surface lattice strain. The dealloyed closedporous He-deposited sample was shown to be durable over five cycles.