High-durability, high-activity electrocatalysts for both polymer electrolyte fuel cells and water electrolyzers are developed by utilization of electronically conducting ceramic nanoparticles. These electrocatalysts require the function of a gas diffusion electrode, which in turn requires electronically conducting pathways, gas diffusion pathways, high surface area and durability at high electrode potentials. The electronically conducting ceramic nanoparticles should be modified to mitigate the resistivity originating from gas adsorption, quantum size effects, and interfacial contact between nanoparticles. The specific microstructure, interface structure, electronic state and crystallinity of the electronically conducting ceramic nanoparticles should also be controlled toward the specific application of the electrocatalyst. These electronically conducting ceramic nanoparticles have demonstrated promising possibilities toward their application in green hydrogen technology.

A novel environmentally friendly inorganic yellow-orange pigment, LiCeW_2−xMn_xO_8−δ (0 ≤ x ≤ 0.07), was synthesized and its optical and color properties were investigated. By partially substituting Mn, a promising source of orange-red coloration, into the octahedrally coordinated W site of the LiCeW₂O₈ host lattice, the absorption intensity of d–d transitions associated with W and Mn in octahedral coordination was modulated, thereby enabling control over light reflection in the visible spectrum. X-ray photoelectron spectroscopy and Rietveld refinement suggested that the electronic states of the constituent elements may have influenced the d–d transition absorption intensities of W^(6−δ)+ and Mn^(4−δ)+ species, thereby altering the overall light absorption behavior. As a result, the reflectance of LiCeW_1.97Mn_0.03O_8−δ was selectively enhanced in the red region, yielding the most vivid and bright orange pigment.

Ceramic proton conductors have attracted increasing attention due to their potential to improve the efficiency of electrochemical devices, such as fuel cells. BaSc_0.8Mo_0.2O_2.8 exhibits high proton conductivity, however, it is not fully hydrated, resulting in a low proton carrier concentration. Here, we report the full hydration and high proton concentration of a new material, large-sized Lu-substituted BaSc_0.8Mo_0.2O_2.8 (BaSc_0.6Lu_0.2Mo_0.2O_2.8). Due to the larger ionic radius of Lu³⁺ than Sc³⁺, the lattice volume of BaSc_0.6Lu_0.2Mo_0.2O_2.8 was larger than that of BaSc_0.8Mo_0.2O_2.8, which can be responsible for the full hydration and higher water uptake of BaSc_0.6Lu_0.2Mo_0.2O_2.8 compared with BaSc_0.8Mo_0.2O_2.8. The bulk conductivity of BaSc_0.6Lu_0.2Mo_0.2O_2.8 (0.01 S cm⁻¹ at 400 °C) was higher than that of the leading materials such as BaZr_0.8Y_0.2O_2.9 and BaCe_0.9Y_0.1O_2.95 (e.g., 19 times higher than BaCe_0.9Y_0.1O_2.95 at 243 °C). This is attributable to the higher proton concentration 0.40 of BaSc_0.6Lu_0.2Mo_0.2O_2.8 compared with 0.17 of BaZr_0.8Y_0.2O_2.9 and 0.08 of BaCe_0.9Y_0.1O_2.95. The bulk conductivity of BaSc_0.6Lu_0.2Mo_0.2O_2.8 was lower than that of BaSc_0.8Mo_0.2O_2.8 and BaSc_0.8W_0.2O_2.8 due to its lower proton diffusion coefficient D. The D of BaSc_0.6Lu_0.2Mo_0.2O_2.8 exhibited a non-Arrhenius behavior, and its activation energy for D increased with decreasing temperature, which is attributable to proton trapping.

Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode material to suppress the shuttle effect, as the active sulfur in SPAN is atomically dispersed and covalently bonded to the conductive skeleton, thereby eliminating the presence of elemental sulfur. This structure significantly reduces the dissolution of lithium polysulfides into the electrolyte during cycling. To enhance our understanding of the charge–discharge mechanism of SPAN, this study employed transmission electron microscopy (TEM) to investigate and analyze the microstructural changes in SPAN. Our findings revealed that SPAN particles undergo repeated expansion and contraction, leading to the expansion and closure of internal cracks. Li₂S nanocrystals appear in SPAN with lithiation and remain even when SPAN is fully delithiated. In parts of regions, sulfur migrates and accumulates at crack boundaries in the SPAN particles, forming Li₂S nanocrystals with sizes ranging from 20 to 50 nm. These Li₂S nanocrystals also persist even when SPAN is fully delithiated. The accumulation of sulfur and Li₂S at boundaries hinders lithium-ion transport, preventing lithiation of the internal SPAN regions and causing electrochemically inactive zones. Consequently, this contributes to capacity fading and limits the overall battery performance.

In two-dimensional protonated layered Zr phosphates, H⁺ ion exchange with monovalent alkali metal ions (M⁺) of smaller atomic radii (e.g., Li⁺, Na⁺) in aqueous solution proceeds much more easily than with larger ions (e.g., K⁺, Rb⁺, and Cs⁺). Therefore, this study investigated the preparation of M₂ZrP₂O₈·nH₂O (M: Li, Na) and M₂ZrP₂O₈·nH₂O (M: K, Rb, Cs) powders via ion substitution—from H⁺ to Li⁺ and Na⁺ in γ-Zr(PO₄)(H₂PO₄)-2H₂O in aqueous solution—and solid-state reactions, respectively. The prepared M₂ZrP₂O₈·nH₂O (M: Li, Na) was monoclinic with a thin plate-like crystal morphology, whereas M₂ZrP₂O₈·nH₂O (M: K, Rb, Cs) was tetragonal with a thick plate-like crystal morphology. Further analyses revealed (002) or (001) peaks, indicating an interlayer distance of approximately 5–10°. Moreover, the interlayer distance of M₂ZrP₂O₈·nH₂O (M: Li, Na) exceeded that of M₂ZrP₂O₈·nH₂O (M: K, Rb, Cs). Finally, the ionic conductivity of M₂ZrP₂O₈·nH₂O (M: K, Rb, Cs) at 30–80 °C exceeded that of M₂ZrP₂O₈·nH₂O (M: Li, Na) by approximately 1.5 orders of magnitude, while the apparent activation energy for ionic conduction was lower. The ionic conductivities of M: K, Rb, and Cs at room temperature were found to be 1.2 × 10⁻³, 9.1 × 10⁻⁴, and 1.3 × 10⁻³ S·cm⁻¹, respectively.