Electrochemical characterization of the Pt/β′′–Al2O3 system under conditions of in situ electrochemical modification of catalytic activity for propane combustion

Abstract

Linear sweep and cyclic voltammetry were used for electrochemical characterization of the Pt/sodiumb 00 -Al 2 O 3 system and investigation of the phases formed upon electrochemical pumping of sodium ions to the Pt catalyst-electrode under conditions of propane combustion or under mixtures of O 2 or CO 2 with helium, at temperatures between 320 and 480°C. The number, position and magnitude of the peaks in the obtained voltammograms were found to depend on gas phase composition, temperature, and pre-scan (initial polarization) conditions. The results showed that under conditions of propane combustion more than one sodium phases can be formed as a result of electrochemical pumping of sodium ions to the Pt catalyst. The related electrochemical reactions and the identity of these sodium phases, which correspond mainly to carbonate or bicarbonate phases but also to oxide phases, are discussed on the basis of the obtained results and those of former studies.

Electropositive Promotion by Alkalis or Alkaline Earths of Pt-Group Metals in Emissions Control Catalysis: A Status Report

“…This poisoning effect of electropositive promoters on Pt for alkanes oxidation can be attributed to the weak adsorption of alkanes compared to oxygen. A latter study published by the same authors dealt with the electrochemical characterization of the aforementioned catalytic system [49]. In this work they observed, in good agreement with some of the studies mentioned above, that the sodium promoter is on the metal surface mainly forming carbonate, bicarbonate and oxide phases.…”

“…The adsorption of these electrophobic adsorbates is being even worse on alkali-modified electron enriched surfaces. This makes the generally observed alkali-induced poisoning of alkanes oxidation reactions readily understandable, no matter of what oxidant agent (oxygen or NO) used [48,49,65,66].…”

Enhancing the catalytic activity and selectivity of the partial oxidation of methanol by electrochemical promotion

“…1 (CH 3 OH/O 2 = 7.2%/4.6%, 320°C). As already demonstrated in previous studies with alkali electro-promoted systems [28][29][30], the cathodic part of the cyclic voltammetry (negative potentials) could be linked with the migration of ions from the solid electrolyte to the catalyst-working electrode surface with the consequent formation of promoter-derived surface compounds after interaction with the chemisorbed species. On the other hand, the anodic part of the cyclic voltammetry could be linked to the decomposition of the previously formed species and the migration of the ions back to the solid electrolyte.…”

“…On the other hand, the anodic part of the cyclic voltammetry could be linked to the decomposition of the previously formed species and the migration of the ions back to the solid electrolyte. Thus, taking into account that the gold counter electrode is constituted by big particles of negligible activity, all the electrochemical processes displayed on the voltammetry could be mainly attributed to the formation and decomposition of surface compounds on the Pt catalyst-working electrode [30]. Without entering in a deep analysis on the nature of the different electrochemical processes that occur on the Pt catalyst-working electrode film, one can observe a much higher electrocatalytic activity (much higher cathodic and anodic peaks) for the case of the Pt impregnated film vs. the Pt film prepared by CAD, probably due, as commented above, to a higher tpb length of the former (porous film calcined at high temperature 450°C).…”

Facile preparation of Cu–Mn/CeO2/SBA-15 catalysts using ceria as an auxiliary for advanced oxidation processes

“…Porous materials are attractive because of their large accessible surface areas with exposed sites for metal oxide particle deposition to improve dispersibility. Porous materials, such as activated carbon, 19 zeolites, 20 and b-Al 2 O 3 , 21 have been employed as the matrix for the nanoparticles. However, poor activity for AOP reactions was observed due to diffusion limitations of the reactants in these irregular micropores.…”