Operation of hydrogen–air fuel cells based on proton conducting oxides and hydrogen storage metals

Abstract

Abstract We constructed a hydrogen–air fuel cell consisting of proton conducting oxides as an electrolyte and hydrogen storage metals as a hydrogen source. By using the hydrogen storage metals as the hydrogen source, we could test very easily both the electrolyte and the electrode materials. We tested three kinds of proton conducting oxides, i.e. SrCe 0.95 Yb 0.05 O 2.975 , SrZr 0.9 Yb 0.1 O 2.95 and BaCe 0.9 Y 0.1 O 2.95 as well as two kinds of the negative electrode materials, i.e. graphite and nickel pastes. The fuel cell operated stably giving open circuit voltages of about 1.2 V, when the cell was maintained near a specific temperature at which hydrogen gas of about 0.1 MPa was released from the hydrogen storage metal. Under load, current densities varied depending on the kind of proton conducting oxides as well as on the negative electrode materials. Also the current densities varied with temperature and the thickness of electrolyte. The best current density–voltage performance was obtained from the fuel cells based on BaCe 0.9 Y 0.1 O 2.95 and nickel paste. The highest current density at 700 mV, 31.6 mA cm −2 , was delivered by a cell of 0.9 mm electrolyte thickness at 640°C.