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

High concentrations of proton carriers (5.0 × 1021 cm− 3) were injected into tungsten phosphate glass (8WO3-35NaO1/2-8NbO5/2-5LaO3/2-44PO5/2) 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.