Synthesis, Characterization, and Proton Conduction Behavior of Thorium and Cerium Phosphonates

Abstract

Thorium (Th 4+ ) and cerium (Ce 4+ ) phosphonates have been synthesized by the sol–gel method using various phosphonic acids and analyzed using elemental and CHN analysis, spectral analysis (Fourier transform infrared spectroscopy and X-ray diffraction), thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The proton transport study was performed by measuring proton conductance at different temperatures using an impedance analyzer. The Grotthuss mechanism of the proton conduction has been discussed thoroughly on the basis of results obtained from the impedance measurement; the specific proton conduction (σ) and activation energy ( E a ) have been evaluated and compared with the reported proton-conducting system having similar phosphonate moieties.

Layered Lanthanide Sulfophosphonates and Their Proton Conduction Properties in Membrane Electrode Assemblies

“…Recent interest in phosphonate-based coordination polymers (CPs) relies on chemical robustness and functional versatility of metal phosphonate materials, which make them attractive for a number of potential applications. − Among the CP-based proton conductors, metal phosphonates hold a prominent position. − Such materials are sought due to their attractive properties such as: (a) hydrolytic stability of the P–C and M–O bonds, , (b) stability to higher temperatures, (c) structures with well-defined proton conduction pathways, − (d) acidic sites on the ligands, − or (e) presence of lattice water molecules that commonly participate in the proton conduction mechanism. − Efforts have been put forth to enhance the proton conduction efficiency by introducing acidic moieties into the phosphonate ligand backbone , or by replacing the phosphonate ligand altogether with another that possesses (more) acidic groups. , One prominent example is the sulfonate group. Metal phosphonates containing sulfonate groups have been among the first such materials that were studied for proton conductivity .…”

Dual‐Proton Conductor for Fuel Cells with Flexible Operational Temperature

“…[32,33] In the presence of a proton source, N atoms can act as proton acceptors and participate in mass transfer. [34] Among the OPAs, EDTMPA is a quaternary acid with amphoteric properties, [28] with its first-order dissociation constant (pK a1 = 2.3) close to that of PA (pK a1 = 2.12). Therefore, theoretically, EDTMPA has a good ability for self-dissociation of protons.…”

“…Organic phosphonic acid (OPA) is a small acidic molecule that replaces -OH in PA with an organic functional group to form C-P bonds. [26][27][28] OPAs have a large molecular weight and low solubility in water, causing the molecular dynamic migration of OPAs to be lower than that of PA. [27] In addition, OPAs have dissociation constants (pK a ) close to or even lower than that of PA, indicating strong acidity. Kreuer et al [29] studied the proton conduction behavior of phenylphosphonic acid compounds substituted with benzene functional groups under high-temperature and anhydrous conditions.…”

Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review

“…[147,[148][149][150] Porous metal phosphonate hybrids have been widely used as highly promising materials in numerous energy-storage reactions (e.g., Li-ion battery, fuel cells, and supercapacitors). [151][152][153][154][155] Porous metal phosphonate electrodes have the following remarkable properties: i) the predefined molecular redox functional groups can be flexibly integrated into pore walls or on the surface to control the redox potential; ii) the well-structured nanopores facilitate the intercalation/deintercalation of electrolyte ions;…”