High-performance ceramic composite electrodes for electrochemical hydrogen pump using protonic ceramics

Ceramic composite electrodes comprising an electron-conducting ceramic (Sr-doped LaVO3), a protonic ceramic [Cu and Y-doped Ba(Ce,Zr)O3], and small amounts of CeO2 and Pd as catalysts were fabricated using an infiltration method for use in an electrochemical hydrogen pump and the hydrogen fluxes and the faradaic efficiency were measured by analyzing the gas compositions. This composite electrode performed well; the area-specific resistance of the electrode polarization at 1 A cm−2 was just 0.15 Ω cm2 at 973 K in hydrogen pumping mode, and the overpotential at a large current density of 2 A cm−2 was only about 1.1 V at 973 K. To optimize the operating conditions, the effects of the steam vapor pressure and hydrogen partial pressure on the electrochemical performance of the hydrogen pump were investigated. The steam in the sweep side was consumed by the steam electrolysis due to the partial oxygen conductivity. Therefore, supplying insufficient steam to the cathode was found to cause a steep increase in the voltage at high currents owing to a decrease in the proton conductivity.