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Highlights: [•] Sodium added on Pt/YSZ system affects catalytic and electrocatalytic properties. [•] Proposed model considers work-function changes by promoter species independently. [•] High Na coverage causes interaction among promoter species and reaction components. [•] Reaction changes from electrophilic to volcano and electrophobic at high Na coverage. [ABSTRACT FROM AUTHOR]

Abstract: The effect of spillover processes on the activity of a catalyst system consisting of a mixed oxygen ion and electronic conducting support La0.6Sr0.4Co0.2Fe0.8O3− δ and a metal catalyst (Pt) were investigated. Two types of model single-pellet catalysts were used employing Pt deposited on both sides of a dense LSCF disc pellet. One of these single pellets employed highly disperse, physically non-continuous Pt, in contrast to studies on electrochemical promotion, while the other used a low dispersion continuous film. Driving forces for promoter migration were controlled through the manipulation of the oxygen chemical potential difference across the membrane. Catalyst rate modification was observed in all cases. However, it was found that there is a complex relationship between the rate modification, the driving forces for spillover and the geometrical arrangement of the catalyst on the support (i.e. catalyst dispersion). [Copyright &y& Elsevier]

The thermal and chemical expansivity of La 1- x Sr x FeO 3- δ (x ​= ​0.4) was measured using in situ powder neutron and synchrotron X-ray diffraction at temperatures between 932 ​K and 1170 ​K and oxygen partial pressures, P O 2 , between 10−19 ​bar and 0.1 ​bar, giving a wide range of oxygen non-stoichiometry from δ = 0.05 to 0.22. Changes in δ were measured independently using gas analysis. This P O 2 and temperature range covers the material's use as a chemical looping oxygen carrier, a sensor material and in solid oxide fuel cells. Thermal and chemical expansivities were found to be dependent on the oxygen non-stoichiometry, δ. For δ ​< ​0.2 and T ​= ​932–1050 ​K, the linear thermal expansivity was 5.72(4) ​× ​10−5 ​Å/K and the linear chemical expansivity was 0.144(9) Å per unit change in δ. For δ ​> ​0.2 and T ​= ​973–1173 ​K, the linear thermal expansivity increases to 6.18(8) ​× ​10−5 ​Å/K. For δ ​> ​0.2, the linear chemical expansivity varies with both δ and temperature. Image 1 • The chemical and thermal expansivity of La 0.6 Sr 0.4 FeO 3- δ was determined using in situ powder neutron and synchrotron XRD. • The temperature and oxygen partial pressure ranges used were T = 932–1173 K and P O 2 = 10−19–0.1 bar. [ABSTRACT FROM AUTHOR]