The performance of several negative ͑fuel͒ and positive ͑air͒ electrode compositions for use in reversible solid oxide fuel cells capable of operating both as a fuel cell and as an electrolyzer was investigated in half-cell and full-cell tests. Negative electrode compositions studied were a nickel/zirconia cermet ͑Ni/YSZ͒ and lanthanum-substituted strontium titanate/ceria composite, whereas positive electrode compositions examined included mixed ion-and electron-conducting lanthanum strontium ferrite ͑LSF͒, lanthanum strontium copper ferrite ͑LSCuF͒, lanthanum strontium cobalt ferrite ͑LSCoF͒, and lanthanum strontium manganite ͑LSM͒. While titanate/ceria and Ni/YSZ electrodes performed similarly in the fuel cell mode in half-cell tests, losses associated with electrolysis were lower for the titanate/ceria electrode. Positive electrodes gave generally higher losses in the electrolysis mode when compared to the fuel cell mode. This behavior was most apparent for mixed-conducting LSCuF and LSCoF electrodes, and discernible but smaller for LSM; observations were consistent with expected trends in the interfacial oxygen vacancy concentration under anodic and cathodic polarization. Full-cell tests conducted for cells with a thin electrolyte ͑7 m YSZ͒ similarly showed higher polarization losses in the electrolysis than fuel cell direction.

Proton exchange membrane (PEM) water electrolysis is a promising energy storage solution by electrochemically splitting water into hydrogen fuel and oxygen. However, the sluggish kinetics, high operating potential, and corrosive acidic environment during the oxygen evolution reaction (OER) require the use of scarce and costly Ir-based oxides, tremendously hampering its large-scale commercialization. Hence, developing active and stable anode catalysts with reduced precious-metal usage is desperately essential. For the first time, we report a group of Y 2−x Ba x Ru 2 O 7 pyrochlore oxides and employ them in acid OER and PEM electrolyzers. We reveal the mechanism for the promoted OER performance of Ba-doped Y 2 Ru 2 O 7 in which partially replacing Y 3+ by Ba 2+ in Y 2 Ru 2 O 7 greatly facilitates the hole-doping effect, which generates massive oxygen vacancy and multivalence of Ru 5+ / Ru 4+ , thus boosting the OER performance of Y 2−x Ba x Ru 2 O 7 . This work provides an effective method and paradigm for improving the electrocatalytic property of pyrochlore oxides.

No abstract

No abstract

No abstract