Coke formation during high-temperature CO2 electrolysis over AFeO3 (A = La/Sr) cathode: Effect of A-site metal segregation

A-site ordered PrBaMn2O5+δ was investigated as a potential cathode for CO2 electrolysis using a La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte. The A-site ordered layered double perovskite, PrBaMn2O5+δ, was found to enhance electrocatalytic activity for CO2 reduction on the cathode side since it supports mixed valent transition metal cations such as Mn, which could provide high electrical conductivity and maintain a large oxygen vacancy content, contributing to fast oxygen ion diffusion. It was found that during the oxidation of the reduced PrBaMn2O5+δ (O5 phase) to PrBaMn2O6−δ (O6 phase), a reversible oxygen switchover in the lattice takes place. In addition, here the successful CO2 electrolysis was measured in LSGM electrolyte with this novel oxide electrode. It was found that this PrBaMn2O5+δ, layered perovskite cathode exhibits a performance with a current density of 0.85 A cm−2 at 1.5 V and 850 °C and the electrochemical properties were also evaluated by impedance spectroscopy.

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Phase Diagram of the W-doped Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 System Around a Morphotropic Phase Boundary Composition

Journal of Materials Research ◽

10.1557/jmr.2002.0160 ◽

2002 ◽

Vol 17 (5) ◽

pp. 1085-1091 ◽

Cited By ~ 1

Author(s):

W. Z. Zhu ◽

M. Yan ◽

A. L. Kholkin ◽

P. Q. Mantas ◽

J. L. Baptista

Keyword(s):

High Temperature ◽

Phase Boundary ◽

Morphotropic Phase Boundary ◽

Room Temperature ◽

X Ray Diffraction ◽

X Ray ◽

Electrical Neutrality ◽

Phase Boundary Composition ◽

A Site ◽

Successive Phase

The morphotropic phase boundary (MPB) composition that is characterized by the coexistence of rhombohedral and tetragonal phases in the Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 system was modified by W-doping at the B site of a perovskite structural block. To maintain the electrical neutrality, creation of A-site vacancies was intentionally introduced in the formulation of the examined compositions. Incorporation of W ions was revealed to stabilize the tetragonal phase against the rhombohedral one, shifting the MPB toward the PZN-rich end at room temperature. High-temperature x-ray diffraction examination in combination with dielectric measurements discloses two successive phase transitions as a sample is cooled from high temperature, namely, paraelectric cubic to ferroelectric rhombohedral followed by ferroelectric rhombohedral to ferroelectric tetragonal. W addition appears to suppress the first transition while promoting the second one.

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Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

Mineralogical Magazine ◽

10.1180/002646100549166 ◽

2000 ◽

Vol 64 (2) ◽

pp. 255-266 ◽

Cited By ~ 10

Author(s):

J. J. Reece ◽

S. A. T. Redfern ◽

M. D. Welch ◽

C. M. B. Henderson

Keyword(s):

Crystal Structure ◽

Phase Transition ◽

New York ◽

High Temperature ◽

Powder Diffraction ◽

Elevated Temperatures ◽

Neutron Powder Diffraction ◽

Site Preference ◽

A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

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