Solid oxide electrolysis cells can theoretically achieve high energy-conversion efficiency, but current density must be further increased to improve the hydrogen production rate, which is essential to realize widespread application. Here, we report a structure technology for solid oxide electrolysis cells to achieve a current density higher than 3 A cm⁻², which exceeds that of state-of-the-art electrolyzers. Bimodal-structured nanocomposite oxygen electrodes are developed where nanometer-scale Sm_0.5Sr_0.5CoO_3−δ and Ce_0.8Sm_0.2O_1.9 are highly dispersed and where submicrometer-scale particles form conductive networks with broad pore channels. Such structure is realized by fabricating the electrode structure from the raw powder material stage using spray pyrolysis. The solid oxide electrolysis cells with the nanocomposite electrodes exhibit high current density in steam electrolysis operation (e.g., at 1.3 V), reaching 3.13 A cm⁻² at 750 °C and 4.08 A cm⁻² at 800 °C, corresponding to a hydrogen production rate of 1.31 and 1.71 L h⁻¹ cm⁻² respectively.

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu₆₈Al₁₆Zn₁₆(CuAlZn) and Cu₇₃Al₁₅Mn₁₂(CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s⁻¹(adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔT_ad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g⁻¹for the CuAlZn alloy and 5.0 J g⁻¹for the CuAlMn alloy. Potential coefficients of performance (COP_mat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COP_matof approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

The present work investigates electrochemical performance of anode-supported protonic ceramic fuel cells (PCFCs) with composite cathodes consisting of an electronic conductive perovskite oxide and a protonic conductive BaZr _0.1 Ce _0.7 Y _0.1 Yb _0.1 O _{3– δ} (BZCYYb). Although PCFCs are expected as a future high-efficiency device, further higher performance and reliability are essential. Thus, to enhance cathode performance, three conventional perovskite oxides, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _{3– δ} (LSCF), La _0.6 Sr _0.4 CoO _{3– δ} (LSC), and La _0.6 Ba _0.4 CoO _{3– δ} (LBC), that are commonly used in traditional solid oxide fuel cells, are evaluated here as the electronic conductive phase in cathodes containing BZCYYb. Results show that all three of these electronic conductive perovskite oxides are compatible with BZCYYb and stably function as a cathode in PCFC operation. Comparison among these three composite cathodes reveals that the PCFC with the LBC-BZCYYb cathode demonstrate the highest performance, e.g., maximum power densities of 0.57 W cm ⁻² at 600 °C and 1.0 W cm ⁻² at 700 °C. In addition, impedance spectra and fitting analysis reveal that the low electrode polarization resistance in the lower frequency range of the LBC-BZCYYb cathode contributes to the PCFC performance. In summary, composites of perovskite oxides, particularly LBC-BZCYYb, are suitable as cathode material to achieve high performance as well as stable operation in PCFCs.

A NASICON-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) electrolyte sheet for all-solid-state batteries was fabricated by a cold sintering process (CSP). The microstructure of the LATP sheet was controlled to improve the wettability which is an essential factor in CSP. The porous sheets of LATP were prepared by calcination the green sheets to remove the organic components and form the porous structure. By the CSP using the porous sheets, the densification of grain boundary was observed and further densified with increasing reaction time. The total conductivity of the prepared LATP sheet was improved from 3.0 × 10⁻⁶ S/cm to 3.0 × 10⁻⁴ S/cm due to the formation of necks between the particles at the grain boundary.