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The kinetics of steam reforming of methane were studied on a Ni−ZrO2(Y2O3)−cermet film, at temperatures of 1073−1173 K and methane and steam partial pressures of up to 60 and 5 kPa, respectively. It was found that the reaction exhibits Langmuir−Hinselwood kinetic behavior, corresponding to competitive adsorption of methane (in the form of active carbon species, Cad) and H2O (in the form of adsorbed oxygen species, Oad) on the catalytic surface. Kinetic results concerning methane consumption were explained in the frame of a mechanistic scheme involving two rate-limiting steps. These steps correspond (i) to the activated adsorption of CH4 for the production of active carbon species, Cad, and (ii) to the surface reaction of the adsorbed Cad with the Oad species, originating from the adsorption of H2O, for the production of CO. The relative magnitude of the turnover frequencies of these two rate-limiting steps affects considerably the apparent activation energy of the reaction at different P CH 4 and P H 2 O values as well as the tendency of the reaction system to generate graphitic carbon on the catalytic surface. Regarding CO2 formation rate, the kinetic results were explained by considering as the rate-determining step the surface reaction of the adsorbed COad with adsorbed oxygen species.

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The effect of structural and surface versus bulk properties of Mo-Pt alloys and intermetallic phases taken along their phase diagram upon kinetic and electrocatalytic features for the cathodic hydrogen evolution (HER) has been thoroughly investigated and displayed. All specimens along Mo-Pt phase diagram in broader reversible potential range feature Volmer-Tafel mechanism with the catalytic recombination of Tafel as the rate-determining step (RDS), while further polarization plot in semi logarithmic (vs. log) system shows Volmer-Heyrowski mechanism with the electrochemical desorption of Heyrowski reaction being the RDS; the extension of the former depends on the degree of MoO3 coverage and blocking active centers of electrode surface. XPS, UPS, XRD and work function characterization of all specimens revealed congenial volcano plots relative to the same dependence in electrocatalysis. As the main observation the most stable and prevailing Pt content specimens feature the best electrocatalytic and kinetic properties. Activated (MoO3 free) MoPt3 and MoPt4 catalysts feature all along the Tafel plot reversible Tafel catalytic reaction as the RDS, and create properties of super-activity within a broader current density range. It has been pointed out that an intermetallic phase with prevailing Mo atomic percentage (MoPt3) features pronounced electrocatalytic properties for the HER.