Facile Proton Transport in Ammonium Borosulfate-An Unhumidified Solid Acid Polyelectrolyte for Intermediate Temperatures

Efficient Proton Conductor Based on Bismuth Oxide Clusters and Polyoxometalates

Developing new solid-state electrolyte materials for improving the proton conductivity remains an important challenge. Herein, a novel two-dimensional layered solid-state proton conductor Bi2O2-SiW12 nanocomposite, based on silicotungstic acid (H4SiW12O40) and Bi(NO3)3·5H2O, was synthesized and characterized. The composite consists of a layered cation framework [Bi2O2]2+ and interlayer-embedded counteranionic [SiW12O40]4-, which forms continuous hydrogen bond (O-H···O) networks through the interaction of adjacent oxygen atoms on the surface of the [Bi2O2]2+ and oxygen atoms of the H4SiW12O40. Facile proton transfer along these pathways endows the Bi2O2-SiW12 (30:1) nanocomposite with an excellent proton conductivity of 3.61 mS cm-1 at 90 °C and 95% relative humidity, indicating that the nanocomposite has good prospects as a highly efficient proton conductor.

Anhydrous proton-conducting imidazole triflate-SiO2 composite

ImidazoleTriflate (ITF)-SiO₂ composites xITF-(100-x)SiO₂ were prepared by planetary ball-milling method. The structure of the composites was studied by TG-DTA, XRD and FT-IR methods. The ionic conductivity was assessed by alternative current (AC) electrochemical impedance measurement. From XRD results, the crystal size of imidazole triflate became smaller as its loading in xITF-(100-x)SiO₂ decreased. With x = 40 weight percent, the calculated crystal size was about 7.3 nm. FT-IR spectra showed the existence of CF₃SO₃ ^-···H⁺ ion aggregates and imidazole-proton bonds. The electrical conductivity of sample x = 50 was about 6.3 × 10^-3 Scm^-1 at 130 °C under anhydrous condition and about 30 times higher than that of sample x = 100.

Polycations Stabilised by Borosulfates: [Au 3 Cl 4 ][B(S 2 O 7 ) 2 ] and the One‐Dimensional Metal [Au 2 Cl 4 ][B(S 2 O 7 ) 2 ](SO 3 )

(SO₄)‐rich silicate analogue borosulfates are able to stabilise cationic cluster‐like and chain‐like aggregates. Single crystals of [Au₃Cl₄][B(S₂O₇)₂] and [Au₂Cl₄][B(S₂O₇)₂](SO₃) were obtained by solvothermal reaction with SO₃, and the electronic properties were investigated by means of density functional theory–based calculations. [Au₃Cl₄][B(S₂O₇)₂] exhibits a cluster‐like cation, and the cationic gold‐chloride strands in [Au₂Cl₄][B(S₂O₇)₂](SO₃) are found to resemble one‐dimensional metallic wires. This is confirmed by polarisation microscopy.

Triple-Vertex Linkage of (BO4 )-Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum-Chemical Investigation of Sr[B3 O(SO4 )4 (SO4 H)]

Borosulfates are classified as silicate analogue materials. The number of crystallographically characterized compounds is still limited, whereas the structural diversity is already impressive. The anionic substructures of borosulfates exhibit vertex-connected (BO₄ )- and (SO₄ )-tetrahedra, whereas bridging between two (SO₄ )- or even between two (BO₄ )-tetrahedra is scarce. The herein presented compound Sr[B₃ O(SO₄ )₄ (SO₄ H)] is the first borosulfate with a triple-vertex linkage of three (BO₄ ) tetrahedra via one common oxygen atom. DFT calculations complement the experimental studies. Bader charges (calculated for all atoms) as well as charge-density calculations give hint to the electron distribution within the anionic substructure and density-of-states calculations support the interpretation of the bonding situation.

High Enhancement in Proton Conductivity by Incorporating Sulfonic Acids into a Zirconium-Based Metal-Organic Framework via "Click" Reaction

Taking a robust zirconium-based metal-organic framework, UiO-66, as a prototype, functional postmodification via the versatile Cu(I)-catalyzed azide-alkyne "click" reaction was carried out, and sulfonic acid groups were successfully grafted into its skeleton. Characterizations revealed that the MOF network was still well maintained after being treated by "clicked" modification. Investigations by electrochemical impedance spectroscopy measurements revealed that its proton conductivity increases exponentially up to 8.8 × 10^-3 S cm^-1 at 80 °C and 98% RH, while those of the UiO-66 and UiO-66-NH₂ are only 6.3 × 10^-6 and 3.5 × 10^-6 S cm^-1, respectively, at the same condition. Additionally, the continuous test shows it possesses long-life reusability. Such a remarkable enhancement on the proton conductivities and high performance in long-life reusability of the resultant MOF demonstrated that the "click" reaction is a facile reaction in postmodification of robust porous materials toward targeted applications, with which highly promising candidates of proton-conductive electrolytes for applying in proton-exchange-membrane (PEM) fuel cell can be achieved.