A reliable and high performance proton-conducting reversible solid oxide cell (P-RSOCs) is developed to generate electricity in a protonic ceramic fuel cell (PCFC) mode and to generate hydrogen gas in a protonic ceramic electrolysis (PCEC) mode in a single electrochemical device. Herein we propose a modified triple conducting (H+/O2-/e(-)) steam (air) electrode through the infiltration of an Sm0.2Ce0.8O2-delta (SDC) oxygen-ionic conductor, because the polarization resistance (R-p) of P-RSOCs mainly comes from the steam (air) electrode in both the operational modes. The SDC-infiltrated nanoparticles on the composite BaCo0.4Zr0.1Fe0.4Y0.1O3+delta (BCZFY)-BaCe0.7Zr0.1Y0.2-xYbxO3-delta (BCZYYb) electrode result in a considerable improvement in the oxygen reduction reaction and oxygen evolution reaction catalytic activity at 600-700 degrees C due to the extension of electrochemical active sites with the increasing of surface area. In addition, the enhanced ionic conduction of a triple conducting composite using infiltrated oxygen-ionic SDC conductors leads to an effective decrease in the R-p (1.388 -> 1.079 Omega.cm(2) at 600 degrees C symmetric cell) with improved cell performance in both the PCFC and PCEC modes. Furthermore, the NiO-BCZYYb anode-supported cell with the SDC-infiltrated composite BCZFY-BCZYYb air electrode shows excellent durability in the PCFC and PCEC modes without any degradation during 250 h each at 650 degrees C. (C) 2019 The Electrochemical Society.