Organic protic ionics based on Nitrilo(trimethylenephosphonic acid) as water-free, proton-conducting materials

Dual-Proton Conductor for Fuel Cells with Flexible Operational Temperature

The properties of proton conductors determine the operating temperature range of fuel cells. Typically, phosphoric acid (PA) proton conductors exhibit excellent proton conductivity owing to their high proton dissociation and self-diffusion abilities. However, at low temperatures or high current densities, water-induced PA loss causes rapid degradation of cell performance. Maintaining efficient and stable proton conductivity within a flexible temperature range can significantly reduce the start-up temperature of PA-doped proton exchange membrane fuel cells. In this study, a dual-proton conductor composed of an organic phosphonic acid (ethylenediamine tetramethylene phosphonic acid, EDTMPA) and an inorganic PA is developed for proton exchange membranes. The proposed dual-proton conductor can operate within a flexible temperature range of 80-160 °C, benefiting from the strong interaction between EDTMPA and PA, and the enhanced proton dissociation. Fuel cells with the EDTMPA-PA dual-proton conductor showed excellent cell stability at 80 °C. In particular, under the high current density of 1.5 A cm-2 at 160 °C, the voltage decay rate of the fuel cell with the dual-proton conductor is one-thousandth of that of the fuel cell with PA-only proton conductor, indicating excellent stability.

Modification of Amorphous Mesoporous Zirconia Nanoparticles with Bisphosphonic Acids: A Straightforward Approach for Tailoring the Surface Properties of the Nanoparticles

The use of readily prepared bisphosphonic acids obtained in few steps through a thio‐Michael addition of commercially available thiols on tetraethyl vinylidenebisphosphonate enables the straightforward surface modification of amorphous mesoporous zirconia nanoparticles. Simple stirring of the zirconia nanoparticles in a buffered aqueous solution of the proper bisphosphonic acid leads to the surface functionalization of the nanoparticles with different kinds of functional groups, charge and hydrophobic properties. Formation of both chemisorbed and physisorbed layers of the bisphosphonic acid take place, observing after extensive washing a grafting density of 1.1 molecules/nm² with negligible release in neutral or acidic pH conditions, demonstrating stronger loading compared to monophosphonate derivatives. The modified nanoparticles were characterized by IR, XPS, ζ‐potential analysis to investigate the loading of the bisphosphonic acid, FE‐SEM to investigate the size and morphologies of the nanoparticles and ³¹P and ¹H MAS NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The functionalization with bisphosphonic acids represents a straightforward covalent approach for tailoring the superficial properties of zirconia nanoparticles, much straightforward compared the classic use of trisalkoxysilane or trichlorosilane reagents typically employed for the functionalization of silica and metal oxide nanoparticles. Extension of the use of bisphosphonates to other metal oxide nanoparticles is advisable.

High temperature proton exchange membrane fuel cells: progress in advanced materials and key technologies

High temperature proton exchange membrane fuel cells (HT-PEMFCs) are one type of promising energy device with the advantages of fast reaction kinetics (high energy efficiency), high tolerance to fuel/air impurities, simple plate design, and better heat and water management. They have been expected to be the next generation of PEMFCs specifically for application in hydrogen-fueled automobile vehicles and combined heat and power (CHP) systems. However, their high-cost and low durability interposed by the insufficient performance of key materials such as electrocatalysts and membranes at high temperature operation are still the challenges hindering the technology's practical applications. To develop high performance HT-PEMFCs, worldwide researchers have been focusing on exploring new materials and the related technologies by developing novel synthesis methods and innovative assembly techniques, understanding degradation mechanisms, and creating mitigation strategies with special emphasis on catalysts for oxygen reduction reaction, proton exchange membranes and bipolar plates. In this paper, the state-of-the-art development of HT-PEMFC key materials, components and device assembly along with degradation mechanisms, mitigation strategies, and HT-PEMFC based CHP systems is comprehensively reviewed. In order to facilitate further research and development of HT-PEMFCs toward practical applications, the existing challenges are also discussed and several future research directions are proposed in this paper.

Theoretical Insights into the Structure of the Aminotris(Methylenephosphonic Acid) (ATMP) Anion: A Possible Partner for Conducting Ionic Media

We present a computational characterisation of Aminotris(methylenephosphonic acid) (ATMP) and its potential use as an anionic partner for conductive ionic liquids (ILs). We argue that for an IL to be a good candidate for a conducting medium, two conditions must be fulfilled: (i) the charge must be transported by light carriers; and (ii) the system must maintain a high degree of ionisation. The result trends presented herein show that there are molecular ion combinations that do comply with these two criteria, regardless of the specific system used. ATMP is a symmetric molecule with a total of six protons. In the bulk phase, breaking the symmetry of the fully protonated state and creating singly and doubly charged anions induces proton transfer mechanisms. To demonstrate this, we used molecular dynamics (MD) simulations employing a variable topology approach based on the reasonably reliable semiempirical density functional tight binding (DFTB) evaluation of the atomic forces. We show that, by choosing common and economical starting compounds, we can devise a viable prototype for a highly conductive medium where charge transfer is achieved by proton motion.