Publication date: 10th April 2024
Oxide-ion and proton conductors have found diverse applications such as in electrolytes of solid-oxide, proton-conducting, and hybrid-ion fuel cells. Research of fuel cells with higher energy efficiency at lower operating temperature has stimulated the search for ion conductors and improved the understanding of the ion-diffusion mechanism. Ion conduction in hexagonal perovskite-related materials is rare, and the mechanism of ion diffusion is unclear. Herein, we report high oxide-ion and proton conductivity (bulk conductivities in wet air: 11 and 2.7 mS cm−1 at 537 and 326 °C, respectively), high chemical, and electrical stability in a new hexagonal perovskite-related oxide Ba7Nb3.8Mo1.2O20.1. Total direct current conductivity at 400 °C in wet air of Ba7Nb3.8Mo1.2O20.1 was 13 times higher than that of Ba7Nb4MoO20. We also report a unique dimer-mediated cooperative mechanism of the high oxide-ion conduction of Ba7Nb3.8Mo1.2O20.1 (bulk conductivities in dry air: 10 mS cm−1 at 593 °C and 1.1 mS cm−1 at 306 °C). Ab initio molecular dynamics (AIMD) simulations, neutron-diffraction experiments at 800 °C, and neutron scattering length density analyses of Ba7Nb3.8Mo1.2O20.1 indicated that the excess oxygen atoms are incorporated by the formation of both 5-fold coordinated (Nb/Mo)O5 monomer and its (Nb/Mo)2O9 dimer with a corner-sharing oxygen atom and that the breaking and reforming of the dimers lead to the high oxide-ion conduction in the oxygen-deficient BaO2.1 c′ layer. The long distance between Nb/Mo and Ba cations sandwiching the c′ layer of Ba7Nb3.8Mo1.2O20.1 was found to be responsible for its low activation energy for oxide-ion conduction, leading to high conductivity at low temperatures. AIMD simulations showed that high proton conduction can be attributed to proton migration in the hexagonal close-packed BaO3 layers of Ba7Nb3.8Mo1.2O20.1. The present findings hold a great promise for the development and design of ion conductors.
We thank Dr. S. Torii, Dr. T. Kamiyama, and Dr. S. Lee for their assistance in the neutron-diffraction experiments. We express special thanks to Mr. T. Tsujiguchi, Dr. W. Zhang, Dr. H. Yaguchi, Mr. R. Inoue, Mr. H. Tejima, Mr. K. Saito, and Mr. K. Matsuzaki for useful discussion and assistance in the experiments/analyses. We would like to acknowledge Kojundo Chemical Laboratory Co. Ltd. for arrangements of the ICP measurements and providing raw materials. We thank Dr. S. Iguchi for the assistance in the XPS measurements. We also thank Ms. K. Suda for measurements of thermogravimetrymass spectroscopy (TG-MS). We acknowledge Dr. M. Tada for measurements of Raman spectra. We thank Mr. M. Ohkawara for the assistance in neutron-diffraction measurements at HERMES and the support from the Center of Neutron Science for Advanced Materials, Institute for Materials Research, Tohoku University. Neutron-diffraction measurements were carried out by the project approval (JPARC: Proposal Nos. 2017L1301, 2017L1302, 2020L801; ANSTO: Proposal No. PP5198; JAEAISSP (JRR-3): Proposal Nos. 22410(IRT), 22603, 22610, 22614, 21578).
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.