Proton conducting tungsten phosphate glass and its application in intermediate temperature fuel cells

Abstract

Abstract High concentrations of proton carriers (5.0 × 10 21 cm − 3 ) were injected into tungsten phosphate glass (8WO 3 -35NaO 1/2 -8NbO 5/2 -5LaO 3/2 -44PO 5/2 ) by electrochemical substitution of sodium ions with protons at 345 °C. The electromotive force of a hydrogen concentration cell that used the substituted glass as a solid electrolyte indicated a mixed conduction of protons and electrons in the glass with a mean proton transport number of 0.8 at 300 °C. The partial conductivity of the protons was 8.0 × 10 − 4 Scm − 1 . The fuel cell generated electricity at a maximum power density of 1.3 mWcm − 2 , even though its open circuit voltage was only 0.77 V because of the electronic contribution to the conductivity. Methods to increase the proton conductivity for improving fuel cell performance are discussed.