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A reconfigurable phononic crystal (PnC) is proposed where elastic properties can be modulated by rotation of asymmetric solid scatterers immersed in water. The scatterers are metallic rods with a cross section of 120◦ circular sector. Orientation of each rod is independently controlled by an external electric motor that allows continuous variation of the local scattering parameters and dispersion of sound in the entire crystal. Due to asymmetry of the scatterers, the crystal band structure possesses highly anisotropic band gaps. Synchronous rotation of all the scatterers by a definite angle changes the regime of reflection to the regime of transmission and vice versa. The same mechanically tunable structure functions as a gradient index medium by incremental, angular reorientation of rods along both row and column, and, subsequently, can serve as a tunable acoustic lens, an acoustic beam splitter, and finally an acoustic beam steerer. 

In this work, a robust solid oxide electrolysis cell with Sr 2 Fe 1.5 Mo 0.5 O 6−δ –Ce 0.8 Sm 0.2 O 1.9 (SFM–SDC) based electrodes has been utilized to verify the conceptual process of partial oxidation of methane (POM) assisted steam electrolysis, which can produce syngas and hydrogen simultaneously. When the cathode is fed with 74%H 2 –26%H 2 O and operated at 850 °C, the open circuit voltage (OCV), the minimum energy barrier required to overcome the oxygen partial gradient, is remarkably reduced from 0.940 to −0.012 V after changing the feed gas in the anode chamber from air to methane, indicating that the electricity consumption of the steam electrolysis process could be significantly reduced and compensated by the use of low grade thermal energy from external heat sources. It is found that after ruthenium (Ru) impregnation, the electrolysis current density of the electrolyzer is effectively enhanced from −0.54 to −1.06 A cm −2 at 0.6 V and 850 °C, while the electrode polarization resistance under OCV conditions and 850 °C is significantly decreased from 0.516 to 0.367 Ω cm 2 . Long-term durability testing demonstrates that no obvious degradation but a slight improvement is observed for the electrolyzer, which is possibly due to the activation of the SFM–SDC electrode during operation. These results indicate that the robust Ru infiltrated solid oxide electrolyzer is a very promising candidate for POM assisted steam electrolysis applications. Our result will provide insight to improve the electrode catalysts used in POM assisted steam electrolysis. 

Electron doping in perovskites is an effective approach to design and tailor the structure and property of materials. In A 2 BB′O 6−δ -type double perovskites, B-site cation order can be tunable by A-site modification, potentially leading to significant effect on the oxygen nonstoichiometry of the compounds. La 3+ -doped Sr 2 FeMoO 6−δ (Sr 2−x La x FeMoO 6−δ , SLFM with 0 ≤ x ≤ 1) double perovskites have been designed and characterized systematically in this study as anode materials for solid oxide fuel cells. Rietveld refinement of powder X-ray diffraction reveals a crystalline symmetry transition of SLFM from tetragonal to orthorhombic with the increase of La content, driven by the extra electron onto the antibonding orbitals of e g and t 2g of Fe/Mo cations. An increase in Fe/Mo anti-site defect accompanies this phase transition. Solid oxide fuel cells incorporating the Sr 1.8 La 0.2 FeMoO 6−δ (SLFM2) anode demonstrate impressive power outputs and stable performance under direct CH 4 operation because of its altered electronic structure, desired oxygen vacancy concentration and enhanced reducibility. Density functional theory plus U correction calculations provide an insight into how La doping affects the Fe/Mo anti-site defects and consequently the oxygen transport dynamics. 

Abstract The proton‐conducting solid oxide electrolysis cell (H‐SOEC) is a promising device that converts electrical energy to chemical energy. H‐SOECs have been actively studied in the past few years, due to their advantages over oxygen‐ion‐conducting solid oxide electrolysis cells (O‐SOECs), such as lower operation temperature, relatively lower activation energy, and easier gas separation. A critical overview of recent progress in H‐SOECs is presented, focusing particularly on the period from 2014 to 2018. This review focuses on three aspects of H‐SOECs, namely, the materials, modeling, and current leakage in proton conducting oxide electrolytes. Specifically, the current leakage in proton conducting oxides, which is often neglected, leads to two problems in the studies of H‐SOECs. One is the distortion of the electrochemical impedance spectra and the other is low faradaic efficiency of electrolysis. Based on the comprehensive and critical discussion in these three sections, challenges in the development of H‐SOECs are highlighted and prospective research in H‐SOECs is outlined.