skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Quantifying and elucidating the effect of CO 2 on the thermodynamics, kinetics and charge transport of AEMFCs
It has been long-recognized that carbonation of anion exchange membrane fuel cells (AEMFCs) would be an important practical barrier for their implementation in applications that use ambient air containing atmospheric CO 2 . Most literature discussion around AEMFC carbonation has hypothesized: (1) that the effect of carbonation is limited to an increase in the Ohmic resistance because carbonate has lower mobility than hydroxide; and/or (2) that the so-called “self-purging” mechanism could effectively decarbonate the cell and eliminate CO 2 -related voltage losses during operation at a reasonable operating current density (>1 A cm −2 ). However, this study definitively shows that neither of these assertions are correct. This work, the first experimental examination of its kind, studies the dynamics of cell carbonation and its effect on AEMFC performance over a wide range of operating currents (0.2–2.0 A cm −2 ), operating temperatures (60–80 °C) and CO 2 concentrations in the reactant gases (5–3200 ppm). The resulting data provide for new fundamental relationships to be developed and for the root causes of increased polarization in the presence of CO 2 to be quantitatively probed and deconvoluted into Ohmic, Nernstian and charge transfer components, with the Nernstian and charge transfer components controlling the cell behavior under conditions of practical interest.  more » « less
Award ID(s):
1803189
PAR ID:
10174741
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Energy & Environmental Science
Volume:
12
Issue:
9
ISSN:
1754-5692
Page Range / eLocation ID:
2806 to 2819
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, Journal of Materials Chemistry A)
    Integration of carbon dioxide capture from flue gas with dry reforming of CH 4 represents an attractive approach for CO 2 utilization. The selection of a suitable bifunctional material serving as a catalyst/sorbent is the key. This paper reports Ni decorated and CeO x -stabilized SrO (SrCe 0.5 Ni 0.5 ) as a multi-functional, phase transition catalytic sorbent material. The effect of CeO x on the morphology, structure, decarbonation reactivity, and cycling stability of the catalytic sorbent was determined with TEM-EDX, XRD, in situ XRD, CH 4 -TPR and TGA. Cyclic process tests were conducted in a packed bed reactor. The results indicate that large Ni clusters were present on the surface of the SrNi sorbent, and the addition of CeO 2 promoted even distribution of Ni on the surface. Moreover, the Ce–Sr interaction promoted a complex carbonation/decarbonation phase-transition, i.e. SrCO 3 + CeO 2 ↔ Sr 2 CeO 4 + CO 2 as opposed to the conventional, simple carbonation/decarbonation cycles ( e.g. SrCO 3 ↔ SrO + CO 2 ). This double replacement crystalline phase transition mechanism not only adjusts the carbonation/calcination thermodynamics to facilitate SrCO 3 decomposition at relatively low temperatures but also inhibits sorbent sintering. As a result, excellent activity and stability were observed with up to 91% CH 4 conversion, >72% CO 2 capture efficiency and ∼100% residual O 2 capture efficiency from flue gas by utilizing the CeO 2 ↔ Ce 2 O 3 redox transition. This renders an intensified process with zero coke deposition. Moreover, the SLDRM with SrCe 0.5 Ni 0.5 has the flexibility to produce concentrated CO via CO 2 -splitting while co-producing a syngas with tunable H 2 /CO ratios. 
    more » « less
  2. ; ; ; ; ; (, Journal of The Electrochemical Society)
    Anion exchange membrane fuel cells (AEMFCs) have been widely touted as a low-cost alternative to existing proton exchange membrane fuel cells. However, AEMFCs operating on air suffer from a severe performance penalty caused by carbonation from exposure to CO2. Many approaches to removing CO2from the cathode inlet would consume valuable energy and complicate the systems-level balance-of-plant. Therefore, this work focuses on an electrochemical solution where CO2removal would still generate power, but not expose an entire AEMFC stack to carbonation conditions. Such a system consists of two AEMFCs in series. The first AEMFC, which acts as an anion exchange CO2separator (AECS), is relatively small and serves to scrub CO2from the air. The AECS is powered by the hydrogen bleed from the second (i.e., main) AEMFC. A small amount of hydrogen is bled from the recycled hydrogen used in the main AEMFC to mitigate impurity build-up, including nitrogen gas from diffusion across its membrane. The second, main AEMFC operates on the purified air output from the AECS and fresh H2. This work shows that it is possible to use an AECS to lower the CO2concentration in the AEMFC input air stream to values low enough that the main AEMFC can be operated stably for extended periods, 150 h in this demonstration. Also, in this study, AEMFCs are operated on AECS-purified air without experiencing a performance penalty. Lastly, the relative geometric active area of the AEMFC and AECS devices are evaluated and discussed. 
    more » « less
  3. ; ; ; (, Journal of Materials Chemistry A)
    Rational design and synthesis of efficient catalysts for electrochemical CO 2 reduction is a critical step towards practical CO 2 electrolyzer systems. In this work, we report a strategy to tune the catalytic property of a metallic Pd catalyst by coating its surface with a polydiallyldimethyl ammonium (PDDA) polymer layer. The resulting PDDA-functionalized Pd/C catalysts exhibit an enhanced CO faradaic efficiency of ∼93% together with a current density of 300 mA cm −2 at −0.65 V versus reversible hydrogen electrode in comparison to non-functionalized and commercial Pd/C catalysts. X-ray photoelectron spectroscopy analysis reveals that the improvement can be attributed to the electron transfer from the quaternary ammonium groups of PDDA to Pd nanoparticles, weakening the CO binding energy on Pd. The weak CO adsorption on Pd was further confirmed by the CO temperature programmed desorption measurement and operando attenuated total reflection-Fourier-transform infrared analysis. Therefore, the incorporation of electron-donating groups could be an effective strategy to decrease the CO binding energy of a metallic catalyst for a high CO selectivity in CO 2 electroreduction. 
    more » « less
  4. ; ; (, Advanced Materials)
    Abstract The utilization of redox‐active gas as cathode materials has been proposed as a promising approach to meet the demand for next‐generation battery technologies. Toward this end, nitrogen oxides (NOx)—inexpensive, abundant gases readily produced from ammonia on an industrial scale—is a promising energy storage media; however, its utilization as cathode material has not been achieved. In this work, the cage effect of NO and NO2radicals are utilized to stabilize the charge product of Li‐NOxcell as N2O3. This cell operates via reversible redox of LiNO3to N2O3, achieving a specific capacity of 1,570 mA h gcarbon−1or 25 mA h cmelectrode−2 at a full cell voltage of 3.85 V with an average energy efficiency of 89% at a current density up to 2 mA cmelectrode−2. These metrics represent one of the highest areal capacity, current density, cell voltage, and energy efficiency reported for a metal‐gas cells. 
    more » « less
  5. ; ; ; ; ; (, AIChE Journal)
    Abstract Portlandite (Ca(OH)2; also known as calcium hydroxide or hydrated lime), an archetypal alkaline solid, interacts with carbon dioxide (CO2) via a classic acid–base “carbonation” reaction to produce a salt (calcium carbonate: CaCO3) that functions as a low‐carbon cementation agent, and water. Herein, we revisit the effects of reaction temperature, relative humidity (RH), and CO2concentration on the carbonation of portlandite in the form of finely divided particulates and compacted monoliths. Special focus is paid to uncover the influences of the moisture state (i.e., the presence of adsorbed and/or liquid water), moisture content and the surface area‐to‐volume ratio (sa/v, mm−1) of reactants on the extent of carbonation. In general, increasing RH more significantly impacts the rate and thermodynamics of carbonation reactions, leading to high(er) conversion regardless of prior exposure history. This mitigated the effects (if any) of allegedly denser, less porous carbonate surface layers formed at lower RH. In monolithic compacts, microstructural (i.e., mass‐transfer) constraints particularly hindered the progress of carbonation due to pore blocking by liquid water in compacts with limited surface area to volume ratios. These mechanistic insights into portlandite's carbonation inform processing routes for the production of cementation agents that seek to utilize CO2borne in dilute (≤30 mol%) post‐combustion flue gas streams. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email