The electronic and crystalline properties of solid complex materials dictate performance in electrochemical applications, such as electrodes or solid electrolytes in solid-state lithium ion power systems. Herein, we perform variable-temperature two-electrode impedance spectroscopy on a variety of nanocrystalline metal oxides to investigate their relative total conductivities and the kinetics of vacancy formation. Lithiated and unlithiated first-row transition metal oxides (manganese, iron, cobalt, and nickel) with various crystal structures, surface areas, and morphologies were investigated. Characterization of these materials by XRD, SEM, and TEM was performed to investigate the physiochemical properties and changes imparted by chemical lithiation, specifically on the textural properties. Activation energies derived from Arrhenius plots were found to vary between 17 and 33kJmol(-1) for the systems studied. Lithiated nickel oxide was observed to provide the lowest activation energy and highest conductivity of the studied systems. The relatively low electrical conductivity suggests conductive additives must be used to facilitate electron transfer in electrodes for these materials; however, the improved conductivity compared to nonporous bulk commercial oxide systems suggests these to be promising active materials for electrochemical applications.

A unique approach for the synthesis of nonstoichiometric, mesoporous molybdenum oxide (MoO 3– x ) with nanosized crystalline walls by using a soft template (PEO‐ b ‐PS) synthesis method is introduced. The as‐synthesized mesoporous MoO 3– x is very active and stable (durability > 12 h) for the electrochemical hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The intrinsic MoO 3 serves as an HER electrocatalyst without the assistance of carbon materials, noble metals, or MoS 2 materials. The results from transmission electron microscopy and N 2 sorption techniques show that the as‐synthesized mesoporous MoO 3– x has large accessible pores (20–40 nm), which are able to facilitate mass transport and charge transfer during HER. In terms of X‐ray diffraction, X‐ray photoelectron spectroscopy, temperature‐programmed oxidation, and diffusive reflectance UV–vis spectroscopy, the mesoporous MoO 3– x exhibits mixed oxidation states (Mo 5+ , Mo 6+ ) and an oxygen‐deficient structure. The as‐synthesized MoO 3– x only requires a low overpotential (≈0.14 V) to achieve a 10 mA cm −2 current density in 0.1 m KOH and the Tafel slope is as low as 56 mV dec −1 . Density functional theory calculations demonstrate a change of electronic structure and the possible reaction pathway of HER. Oxygen vacancies and mesoporosity serve as key factors for excellent performance.

Ceramic Matrix Composites (CMCs) combine the toughness of advanced composites with the high temperature functionality, oxidation resistance and mechanical strength of ceramic materials. These multi-component composites are capable of operating in extreme conditions such as those in power generation, aerospace, and aircraft technologies [1,2]. CMCs are typically composed of three components: reinforcing fiber, interphase, and matrix. The two major classifications of these multicomponent composites are oxide and non-oxide. Oxide CMCs are made with various metal oxide components allowing the CMC to be used in high temperature oxidizing environments without compromising the strength of the material due to unwanted oxidation. Some examples of ceramics used in oxide CMCs are alumina, silica, boria, zirconia and yittria [3]. Non-oxide CMCs can be composed of but are not limited to silicon carbide, boron nitride, titanium diboride, silicon nitride, and carbon [2].