The success of the next generation of anion-exchange membrane fuel cells (AEMFCs) depends on the development of active, reliable, and economical oxygen reduction reaction (ORR) catalysts. Here, we synthesize a series of ultra-low-cost metal-free ORR catalysts by doping a common pristine graphite precursor with chemically singular-type heteroatoms, namely I, S, N, or B, using single-step planetary ball milling technique. All doped-graphites show substantially enhanced ORR performance relative to the pristine (undoped) graphite. Among all the tested catalysts, N-graphite exhibited the highest ORR onset potential of 0.87 V vs. reversible hydrogen electrode. These results are supported by density functional theory calculations. The ORR catalysts also exhibit remarkable
Amine-rich facilitated transport membranes (FTMs) attract great interest in intensifying the membrane-based CO2 separation processes. The high-molecular-weight polyvinylamine (PVAm) polymers containing fixed-site carriers of the amino groups were used to prepare highly CO2-permeable membranes. The sterically hindered PVAm polymers of poly(N-methyl-N-vinylamine) and poly(N-isopropyl-N-vinylamine) were obtained by functionalization of PVAm to provide superior CO2 solubility. By loading the mobile carriers of amino acid salt (AAS) and CO2-philic graphene oxide (GO), the prepared FTMs render enhanced CO2 permeance and CO2/N2 selectivity. The d-spacing of 8.8 Å and the ultramicropores of 3.5 Å from GO nanosheets provide the combination of both selective surface flow and molecular sieving mechanisms to
A facile method for the preparation of precious metal-free catalysts for the oxygen reduction reaction (ORR) from lignin, dicyandiamide, and transition metal salts is presented. Magnesium acetate was employed as a precursor for a sacrificial template, enhancing the porous structure of the catalysts. Iron content in the catalyst materials was optimized and a bimetallic catalyst containing Fe and Co was also prepared. The physicochemical analysis revealed uniform dispersion of various nitrogen moieties and transition metal centers on sheet-like carbon structures, along with some carbon-encapsulated metal-rich nanoparticles. Rotating disc electrode tests in an alkaline solution demonstrated the dependence of the ORR
Ammonia electrooxidation has received considerable attention in recent times due to its potential application in direct ammonia fuel cells, ammonia sensors, and denitrification of wastewater. In this work, we used differential electrochemical mass spectrometry (DEMS) coupled with attenuated total reflection–surface-enhanced infrared absorption (ATR–SEIRA) spectroscopy to study adsorbed species and solution products during the electrochemical ammonia oxidation reaction (AOR) on Pt in alkaline media, and to correlate the product distribution with the surface ad-species. Hydrazine electrooxidation, hydroxylamine electrooxidation/reduction, and nitrite electroreduction on Pt have also been studied to enhance the understanding of the AOR mechanism. NH3, NH2, NH, NO, and NO2 ad-species
Anion-exchange membrane fuel cells and water electrolyzers have garnered significant attention in past years due to their potential role in sustainable and affordable energy conversion and storage. However, the chemical stability of the polymeric anion-exchange membranes (AEMs), the key component in these devices, currently limits their lifespan. Recently, metallopolymers have been proposed as chemically stable alternatives to organic cations, using metal centers as ion transporters. In metallopolymer AEMs, various properties such as alkaline stability, water uptake, flexibility, and performance, are determined by both the metal complex and polymer backbone. Herein we present a systematic study investigating the influence of the
Over the last decade, anion-exchange membrane fuel cells (AEMFCs) have continued to show steady power output and durability improvements at low temperatures of 60oC–80oC. However, AEMFC durability still lags, largely due to the critical issue of water management. High-temperature operation (R100oC) enables simplified water management, but additional material stability challenges remain, particularly concerning the chemical stability of the anionexchange membranes (AEMs). Herein, we report the synthesis of lightly branched poly(arylene piperidinium) AEMs, leading to balanced water management and sufficient stability. The optimized membranes demonstrate high-temperature H2/O2 AEMFC operation at 100oC, with a peak power density of 2 W cm-2 and
The substantial advancements and availability of new cost-effective materials have drawn significant attention to the anion-exchange membrane fuel cell (AEMFC) technology. The anion exchange membrane (AEM) is a core component in AEMFCs, essential for conducting hydroxide ions and controlling water transport between the fuel cell electrodes. In this study, we apply a numerical model to investigate the relationship and sensitivity of AEMFC performance and its stability to key AEM properties. Our findings show that membrane maximum hydration level (λmax) has the most significant impact on AEMFC lifetime, followed by membrane ion-exchange capacity, water diffusivity, and membrane thickness. We also demonstrate the significance of
Nanoconfined anion exchange membranes (AEMs) play a vital role in emerging electrochemical technologies. The ability to control dominant hydroxide diffusion pathways is an important goal in the design of nanoconfined AEMs. Such control can shorten hydroxide transport pathways between electrodes, reduce transport resistance, and enhance device performance. In this work, we propose an electrostatic potential (ESP) approach to explore the effect of the polymer electrolyte cation spacing on hydroxide diffusion pathways from a molecular perspective. By exploring cation ESP energy surfaces and validating outcomes through prior ab initio molecular dynamics simulations of nanoconfined AEMs, we find that we can achieve control over
Anion exchange membrane fuel cells (AEMFCs) have been regarded as a promising low-cost alternative to proton exchange membrane fuel cells (PEMFCs) due to their potential to utilize platinum group metal (PGM) free catalysts and their recently demonstrated improvement in power density. However, the development of highly active and stable PGM-free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline solutions remains a significant challenge. In this study, reactive spray deposition technology (RSDT) is used to fabricate a set of Ni/CeO2/C catalysts, and their activity toward the HOR is investigated as a function of the nanoparticle size. The structural and morphological characterization of as synthesized Ni/CeO2/C catalysts confirms that the RSDT is capable
