Electrochem

Proton exchange or electrolyte membranes (PEMs) are vital parts of low-temperature fuel cells because they govern proton transport, fuel crossover, water management, and the mechanical and chemical durability of the membrane electrode assembly. Although perfluorosulfonic acid membranes, such as Nafion, remain widely employed, their dependence on fluorinated chemistry, hydration-sensitive conductivity, cost, and methanol crossover has stimulated interest in alternative membrane materials derived from renewable resources. Chitosan (CS), a naturally derived polysaccharide containing abundant amino and hydroxyl functional groups, has emerged as a promising platform material for the development of proton-conducting membranes for polymer electrolyte membrane fuel cells (PEMFCs) and direct-methanol fuel cells (DMFCs). This review critically examines recent advances in chitosan-based membranes, with emphasis on cross-linking, inorganic and carbon-based composite formation, incorporation of bio-derived fillers, polymer blending, and ionic liquid modification. The influence of these strategies on proton conductivity, methanol permeability, water absorption, dimensional stability, mechanical characteristics, thermal and chemical stability, and fuel cell performance is discussed in relation to membrane composition and structure. The reviewed studies demonstrate that targeted modification of chitosan can substantially improve individual membrane properties; however, achieving a simultaneous balance between proton transport, fuel-barrier characteristics, mechanical integrity, hydration, and long-term durability remains challenging. Variations in chitosan characteristics, membrane fabrication, testing conditions, and performance evaluation also hinder direct comparison among reported systems. Future research should therefore emphasize standardized characterization, reproducible membrane fabrication, membrane electrode assembly optimization, long-term single-cell testing, and life-cycle assessment. These developments are essential for translating chitosan-based PEMs from being laboratory-scale materials towards durable and practical fuel cell applications.

This study evaluates accelerated stress test (AST) protocols and introduces a framework for translating AST-derived degradation metrics into electrode lifetime predictions for heavy-duty vehicle fuel cells. Catalyst stability across ASTs of varying durations is compared using the electrochemically active surface area (ECSA) loss rate, which remains broadly consistent across catalyst systems and Pt loadings but is extremely sensitive to protocol design and exposure conditions. The corresponding cell performance decay is captured through ECSA loss and its impact on exchange current density and oxygen transport resistance. These degradation pathways are further shaped by catalyst particle size and composition, catalyst–support interactions, the catalyst–ionomer interface, and electrode microstructure. Building on these relationships, a practical procedure is developed to estimate electrode lifetime using the allowable ECSA loss predicted by the degradation model, the measured AST ECSA loss rate, and the duty-cycle lifetime of a reference catalyst with matching Pt loading. To generalize AST outcomes, an acceleration (loss) factor, ALF, is defined as the ratio of electrode lifetime to the AST duration required to reach an equivalent end-of-life ECSA loss. The ALF is uniquely determined by catalyst formulation, Pt loading, AST protocol, duty-cycle characteristics, end-of-life definition, and system-level mitigation strategies.

Pharmaceutical residues in environmental and biological matrices require analytical methods that are both sensitive and portable. Chromatographic techniques struggle to deliver this combination outside a laboratory setting. Screen-printed electrodes (SPEs) meet the portability requirement, but bare SPE surfaces offer limited sensitivity and selectivity on their own. Metal–organic frameworks (MOFs), with high surface area and tunable porosity, are increasingly used to modify SPEs for this purpose. However, their intrinsically poor conductivity usually requires pairing with a carbon or metal nanomaterial. This review synthesizes the literature on MOF-modified SPEs specifically for pharmaceutical analysis, which has not previously been treated as a distinct topic. It examines three principal fabrication routes, drop casting, in-situ growth, and printing-based deposition (ink mixing and inkjet printing), and classifies the resulting materials by metal chemistry into five groups spanning copper-based, bimetallic, MIL- and UiO-series, and MOF-derived frameworks. Reported detection limits across antibiotics, neuropsychiatric and analgesic drugs, chronic disease medications, and anticancer agents span about seven orders of magnitude, from low-micromolar electrocatalytic sensors to picomolar recognition-element-based platforms, a gap this review traces directly to sensing mechanisms. The emerging use of machine learning (ML) for MOF screening and voltammetric signal interpretation is also assessed, and the review closes by identifying reproducibility, inconsistent structural reporting, and the absence of interpretable, transferable models as the field’s principal remaining barriers.