Proton Conductivity and Stability of Ba[sub 2]In[sub 2]O[sub 5] in Hydrogen Containing Atmospheres

Abstract

Ba 2 In 2 O 5 is one of the oxygen deficient ceramic materials widely investigated for both oxygen ion conduction and proton conduction in oxidizing atmospheres. However, its electrochemical properties have not been studied in hydrogen containing atmospheres. In this work, the electrical conductivity of Ba 2 In 2 O 5 in hydrogen containing atmospheres was investigated by ac impedance spectroscopy in the temperature range between 100 and 500°C and compared to its conductivity in air and nitrogen in order to estimate the contribution of proton conductivity to the total conductivity. A stable electrical conductivity of over 0.3 S/cm was achieved in the temperature range of 300-480°C in a 50% vol H 2 /50% vol N 2 atmosphere. Electromotive force measurements ͑and complimentary open circuit cell voltage measurements͒ revealed high proton transport numbers over the temperature range. Ba 2 In 2 O 5 shows chemical stability in hydrogen containing atmospheres at temperatures up to 480°C, while decomposing at higher temperatures. Mechanical instability was noticed in humid atmospheres at 400°C and above. This previously unreported high conductivity in H 2 atmosphere creates an opportunity for use of Ba 2 In 2 O 5 as a proton conductive material for a range of intermediate temperature electrochemical devices.

Preparation and characterization of Ce- and La-doped Ba2In2O5 as candidates for intermediate temperature (100–500°C) solid proton conductors

“…Again, for the as-prepared BIO sample, an effect of water was noticed, in this case as a sharp increase in conductivity. When present, water in the structure is in interaction with the oxygen vacancies and oxygen ions [12,34]. When water is released, hydrogen incorporates directly and interacts with the free oxygen vacancies and ions, significantly improving conductivity.…”

“…When water is released, hydrogen incorporates directly and interacts with the free oxygen vacancies and ions, significantly improving conductivity. The mechanisms are suggested in the literature [12][13][14]34]. The decomposition or reduction of the material were excluded as possible causes for increased conductivity, as no changes in composition or structure were observed by XRD after the test in hydrogen.…”

“…Effect of water and its contribution to the total conductivity is also more enhanced for the BIO sample prepared by the GNP method. In the literature [11,12,34] it is anticipated that this conductivity in hydrogen and humidity is mainly due to the proton conductivity. Therefore, our results suggest that the grain boundary plays an important role in the conduction mechanism of protons, possibly by having a higher concentration of oxygen vacancies in this region.…”

Electrochemical Impedance Spectroscopy of Ba2In2O5: Effect of Porosity, Grain Size, Dopant, Atmosphere and Temperature

“…[1][2][3][4][5][6][7][8][9] Undoped and Ce-doped Ba 2 In 2 O 5 are reported to show oxygen ion conductivity in oxygen and nitrogen atmospheres, as well as protonic conductivity in humid air and hydrogen-containing atmosphere, especially at temperatures below 500…”

Ionic Conduction and Power Generation Characteristics of Pr-Doped Ba2In2O5for Proton-Conducting SOFCs

“…• C. 34 The hydrogen concentration cell condition in their study was as follows: In that study, emf was only observed under a humidified atmosphere. For this non-doped Ba 2 In 2 O 5 , the estimated t H + decreased with increasing temperature, and t H + = 0.74 at 350…”