The effect of the carbon support─Ketjenblack (CKB) and Vulcan (CV)─on the Ni/C catalyst properties toward alkaline hydrogen oxidation reaction (HOR) was investigated. Both Ni/CKB and Ni/CV presented improved catalytic activity with an increase in Ni particle size; however, Ni/CKB showed activity significantly higher than that of Ni/CV at the same particle size. The reason for the difference in the HOR activity due to the types of carbon support was revealed to be the difference in the 3D structure of Ni nanoparticles determined by metal–support interaction, which is changed by the surface structures of carbon supports. These findings bring light to the critical importance of
This study addresses the challenges of power output and durability in anion-exchange membrane (AEM) fuel cells (AEMFCs) through the use of graphene-based materials. Graphene oxide (GO) and partially reduced graphene oxide (prGO) with varying degrees of reduction were synthesized and characterized via Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). AEMs were coated with the synthesized graphene materials and tested with Pt catalyst. The addition of GO and prGO with high degrees of reduction improved power output by 12 % and 5 %, respectively, and increased durability by 29 %. Optimal reduction degree of prGO showed significant improvements,
The increasing global energy demand necessitates the development of sustainable electrochemical energy technologies. Anion-exchange membrane fuel cells (AEMFCs) present a promising alternative to proton-exchange membrane fuel cells (PEMFCs) due to their ability to utilize platinum-group metal (PGM)-free catalysts, which significantly reduce costs and resource dependency. In this work, we prepare various PGM-free catalysts for the oxygen reduction reaction (ORR) via an ionothermal synthesis using cyclodextrin and magnesium nitrate. The synthesis conditions were optimized and the electrocatalysts were investigated with both physical and electrochemical characterization techniques. The catalysts’ ORR performance was assessed using rotating disk electrode (RDE) measurements and single-cell AEMFC
Anion-exchange membrane (AEM) water electrolyzers (AEMWEs) have gained significant attention for their ability to utilize precious-metal-free catalysts and environmentally friendly fluorine-free hydrocarbon polymeric membranes. In this study, we identify and quantify the sources of performance losses in operando AEMWEs using an innovative approach based on electrochemical impedance spectroscopy and MATLAB-based impedance spectroscopy genetic programming. Using this approach, we move beyond conventional equivalent circuit models to develop a proper and analytical model of the distribution function of relaxation times (DFRT), enabling a deeper analysis of Faradaic and non-Faradaic processes. We apply this framework to isolate the critical processes─ohmic, ionic transport, charge transfer, and
Platinum group metal (PGM)-free electrocatalysts have emerged as promising alternatives to replace Pt for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, traditional synthesis methods limit the single-atom site density due to metal agglomeration at higher temperatures. This work explores the preparation of hierarchically porous atomically dispersed electrocatalysts for the ORR. The materials were prepared via ionothermal synthesis, where magnesium nitrate was used to prepare hierarchically porous carbon materials. The in-situ formed Mg-Nx sites were trans-metalated to yield ORR-active Fe-Nx sites. The resulting carbon-based catalysts displayed excellent electrocatalytic activity, attributed to the atomically dispersed Fe-Nx active sites and
Facilitated transport membranes (FTMs) with an ultraselective layer prepared from amine-rich polyvinylamine (PVAm)/2-(1-piperazinyl)ethylamine salt of sarcosine (PZEA-Sar) (denoted by PM) and an amorphous dendritic cross-linked network of PVAm-functionalized poly(ethylene glycol)diglycidyl ether (PEGDGE) (named PP) were designed for CO2 separations. The developed membranes expedited CO2 transport over N2 through the synergistic effect from the induced CO2-philic ethylene oxide groups and highly hydrophilic and polar hydroxyl groups together with the low-crystallinity PP networks, which offer a high diffusion rate for CO2-amine complexes through the membrane and stabilize small molecular mobile carriers via hydrogen bonding. The best (PM/PP-10)/polysulfone (PSf) composite membranes achieved a superior CO2/N2 selectivity of
Poly(arylene piperidinium) (PAP) anion-exchange membranes (AEMs) are attractive platform materials currently used for anion-exchange membrane fuel cells (AEMFCs) and chain branching modifications on PAP polymer structures have recently drawn much attention for effectively regulating the membrane properties. To better understand the influence and interplay of the polymer chain entanglement and free volume effect from various branched architectures, herein, lightly end-branched EB-PTP/TPB AEMs, using poly(p-terphenyl dimethylpiperidinium) (PTP) as the polymer backbone and bulky rigid 1,3,5-triphenylbenzene (TPB) as the branching agent, are designed and compared to previously reported random-branched RB-PTP/TPB and linear-chain PTP membranes. Intrinsic viscosity, bulk density and positron annihilation lifetime
Membrane separation is in the spotlight as one of the most cost-effective technologies without chemicals for carbon capture. This work aims to fabricate thin film composite (TFC) membranes for boosting CO2 separation. Commercial polysulfone (PSf) flat sheet membranes pre-treated with ethanol solutions were used as support materials by coating with amino-functionalized cross-linked polydimethylsiloxane (PDMS) interlayer. It is worth noting that the developed amino-functionalized PDMS interlayer based on a novel wet-coating method to avoid the penetration of coating solution, which provides better compatibility with the coated polyamide selective layer and also the facilitated transport for CO2 permeation. A thin CO2-selective layer was obtained
In fuel cells and electrolyzers, suboptimal proton conductivity and its dramatic drop at low humidity remain major drawbacks in proton exchange membranes (PEMs), including current benchmark Nafion. Sustained through-plane (TP) alignment of nanochannels was proposed as a remedy but proved challenging. We report an anisotropic composite PEM, mimicking the water-conductive composite structure of bamboo that meets this challenge. Micro- and nanoscale alignment of conductive pathways is achieved by in-plane thermal compression of a mat composed of co-electrospun Nafion and poly(vinylidene fluoride) (PVDF) nanofibers stabilizing the alignment. This translates to pronounced TP-enhanced proton conductivity, twice that of pure Nafion at high
Anion-exchange membranes (AEMs), known for enabling the high conductivity of hydroxide anions through dense polymeric structures, are pivotal components in fuel cells, electrolyzers, and other important electrochemical systems. This paper unveils an unprecedented utilization of AEMs in an electrochemical oxygen separation process, a new technology able to generate enriched oxygen from an O2/N2 mixture using a small voltage input. We demonstrate a first-of-its-kind AEM-based electrochemical device that operates under mild conditions, is free of liquid electrolytes or sweep gases, and produces oxygen of over 96% purity. Additionally, we develop and apply a one-dimensional time-dependent and isothermal model, which accurately captures the
