Unique Self-Phosphorylating Polybenzimidazole of the 6F Family for HT-PEM Fuel Cell Application.

High-temperature polymer-electrolyte membrane fuel cells (HT-PEMFCs) are a very important type of fuel cells since they operate at 150-200 °C, making it possible to use hydrogen contaminated with CO. However, the need to improve the stability and other properties of gas-diffusion electrodes still impedes their distribution. Self-supporting anodes based on carbon nanofibers (CNF) are prepared using the electrospinning method from a polyacrylonitrile solution containing zirconium salt, followed by pyrolysis. After the deposition of Pt nanoparticles on the CNF surface, the composite anodes are obtained. A new self-phosphorylating polybenzimidazole of the 6F family is applied to the Pt/CNF surface to improve the triple-phase boundary, gas transport, and proton conductivity of the anode. This polymer coating ensures a continuous interface between the anode and proton-conducting membrane. The polymer is investigated using CO2 adsorption, TGA, DTA, FTIR, GPC, and gas permeability measurements. The anodes are studied using SEM, HAADF STEM, and CV. The operation of the membrane-electrode assembly in the H2/air HT-PEMFC shows that the application of the new PBI of the 6F family with good gas permeability as a coating for the CNF anodes results in an enhancement of HT-PEMFC performance, reaching 500 mW/cm2 at 1.3 A/cm2 (at 180 °C), compared with the previously studied PBI-O-PhT-P polymer.

Formation Kinetics and Antimicrobial Activity of Silver Nanoparticle Dispersions Based on N-Reacetylated Oligochitosan Solutions for Biomedical Applications.

The paper presents the results of the synthesis, a detailed kinetics study, and an investigation of the biological activity of silver nanoparticles (AgNPs) in aqueous solutions of N-reacetylated oligochitosan hydrochloride. UV-visible spectrophotometry and dynamic light scattering were employed to control silver ion reduction. The process was observed to follow a pseudo-first-order law. Transmission and scanning electron microscopy demonstrated that AgNPs ranging in size from 10 to 25 nm formed aggregates measuring 60 to 90 nm, with the aggregate surface coated by a 2-4 nm chitosan shell. X-ray microanalysis and powder X-ray diffractometry were used to study the phase composition, identifying two crystalline phases, nanocrystalline silver and AgCl, present in the dispersions. The antibacterial effect was assessed using the serial dilution method for dispersions with varying degrees of Ag+ conversion. Nanodispersions exhibited significant activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Staphylococcus aureus. Interestingly, the activity did not appear to be heavily influenced by the presence of the AgCl phase or the concentration of Ag+ ions. These synthesized dispersions hold promise for the development of materials tailored for biomedical applications.