A novel, easily synthesized, anhydrous derivative of phosphoric acid for use in electrolyte with phosphoric acid-based fuel cells

We build on the success of phosphoric acid as a fuel cell electrolyte, by designing a variant of the molecular acid that provides increased temperature range without sacrifice of high temperature conductivity or open circuit voltage. This is achieved by introduction of a hybrid component, based on silicon coordination of phosphate groups, which prevents decomposition or water loss to 250 °C, while enhancing free proton motion. We report conductivity studies to 285 °C and full H2/O2cell polarization curves to 226 °C with careful monitoring of fuel consumption. The current efficiency we report (current density per unit of fuel supplied per sec) is as high as the highest on record. A power density of 184 mW cm−2 is achieved at 226 °C with hydrogen flow rate of 4.1 ml min−1.

► A phosphoric acid-based fuel cell liquid electrolyte for T > 200 °C without pressure. ► An unhumidified electrolyte of H3PO4, saturated with a new silicophosphoric acid. ► Polarization curves at 226 °C with OCV >0.95 V, and current densities to 1.0 A cm−2. ► Fuel cell of exceptional current efficiency – burns almost all the available fuel.