No abstract

Protonic conductors are gaining use in solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs) as well as for H2 separation membranes. However, for SOFC/SOEC electrode and membrane applications their performance is limited by low electronic conductivity. One of the most promising classes of ceramic proton conductors, perovskites, have highly-tunable compositions allowing for the optimization of both ionic and electronic conductivity. In this work Pr-doped SrCeO3 was studied over a wide range of oxygen partial pressures (pO2’s) and temperatures to determine its defect properties and conductivity. Under reducing conditions Pr-doped SrCeO3 was found to be chemically and structurally stable, with an optimal Pr doping level of 10%. This composition shows greater conductivity compared to previously reported Eu-doped SrCeO3. Under low pO2 Pr-doped SrCeO3 exhibited n-type behavior as conductivity increased with decreasing pO2, suggesting that the electronic conductivity of SrCeO3 is significantly enhanced by Pr doping. Under high pO2 conditions, Pr-doped SrCeO3 exhibited p-type conductivity with higher conductivity in the presence of water affirming its protonic conductivity. This work validates the use of Pr as a means of enhancing electronic conductivity in proton conducting perovskites.

Power generation from electrochemical devices based on solid oxide fuel cells (SOFCs) is in great demand for both stationary and automotive applications to achieve carbon neutrality goals by 2050. In particular, SOFCs are known for their fuel-flexible operations; for example, SOFCs can operate on simple and complex renewable fuels (such as ethanol, natural gas, jet fuel, propane, etc.). Unlike H2-based fuel cells, liquid and hydrocarbon fuels in SOFCs adopt the existing fuel infrastructure and contribute to reducing greenhouse gas emissions significantly. This article presents the potential of using metal-based SOFCs (metal cells) as highly performing and durable power generators. The metal cells technology could be the most accessible solution for using SOFCs for versatile industrial needs.

Stainless steel interconnects in solid oxide fuel cells can lead to chromium poisoning of the cathode, necessitating the use of protective coatings. Electrophoretic deposition is an efficient method to deposit coatings on substrates with complex microstructures. In this study, four spinel coatings; CuMn2O4, CuNi0.2Mn1.8O4, MnCo2O4, and MnFe0.34Co1.66O4, were deposited by direct-current electrophoretic deposition on flat SUS430 stainless steel substrates. The coatings were evaluated on multiple criteria, including microstructural stability, conductivity, Cr gettering ability, and the ability to act as a diffusion barrier at 700°C and 800°C. It was concluded that CuNi0.2Mn1.8O4 is an excellent candidate at temperatures at and below 700oC, while MnFe0.34Co1.66O4 coatings perform better at higher temperatures.

A hybrid Li-ion capacitor represents an emerging class of devices, which results from the coupling of high-energy-density battery-type electrode materials at one side and high-power EDLC electrode at other side. Here, we develop a simple and scalable method including ball-milling, followed by a heating process to synthesize MoS2/graphene composite material. The structural and morphological analyses were carried out by powder X-ray diffraction analysis and scanning electron microscopy. The composite electrode delivers high specific capacity (725 mAh/g at 0.1 A/g and 265 mAh/g at 5 A/g). The hybrid device composed of MoS2/graphene composite electrode as negative electrode and commercial activated carbon as the positive electrode exhibits a high energy density of 117 Wh/kg at 200 W/kg and a maximum power density of 3.9 kW/kg at 79 Wh/kg. The hybrid device showed a long cycle stable Li storage capacity (62% after 5000 cycles at 1 A/g).