Tubular high-temperature proton conductors: transport numbers and hydrogen injection

Tubes of high-temperature proton conductors [Sr(Zr 0.8Ce 0.2) 0.8In 0.2O 3− x , BaZr 0.9Y 0.1O 3− x and CaZr 0.9In 0.1O 3− x ] were investigated in various gas atmospheres. Transport numbers for selected species were measured and compared with literature values. The electrochemical injection of hydrogen into inert gases was demonstrated. By increasing the proton current, titration curves were obtained analogous to those for strong acid–strong base titrations. The modelling of such curves is presented. Fuel cell operation and steam electrolysis was also demonstrated. Exposure of one side of the tubes to ethanol vapor was found to lead to proton pick-up of the tubes. More drastic effects were observed with acetone vapor, which also produced proton pick-up but also the deposition of undesirable carbonaceous layers.