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Title: The energetics of phosphoric acid interactions reveals a new acid loss mechanism

Abstract

Acid retention of phosphoric acid (PA)-doped proton exchange membranes (PEMs) is one of the critical factors that determine the durability of high temperature PEM fuel cells. However, the mechanism of PA loss in the PEMs in the presence of water is obscure in the context of the energetics of the PA cluster. Here, we study the energetics of PA-benzimidazole acid-base and biphosphate-ammonium ion pairs using density functional theory calculations and 31P NMR experiments to propose a novel PA loss mechanism. The results suggest that the removal of the PA from the membrane does not occur due to the strong interaction of PA-water, but due to the incapability of the base polymers to hold the water and PA beyond a certain level. Significantly higher interaction in the biphosphate-ammonium ion pair shifts the equilibrium PA composition in the PA cluster to higher values, which minimizes the PA loss in the presence of water. Introducing the high interaction with PA molecules provides a path for better PEM design that may allow using high temperature PEM fuel cells with excellent acid retention.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. National Inst. of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1526963
Alternate Identifier(s):
OSTI ID: 1504509
Report Number(s):
LA-UR-18-31799
Journal ID: ISSN 2050-7488; JMCAET
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Materials Chemistry. A
Additional Journal Information:
Journal Volume: 7; Journal Issue: 16; Journal ID: ISSN 2050-7488
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Energy Sciences

Citation Formats

Lee, Albert S., Choe, Yoong-Kee, Matanovic, Ivana, and Kim, Yu Seung. The energetics of phosphoric acid interactions reveals a new acid loss mechanism. United States: N. p., 2019. Web. doi:10.1039/C9TA01756A.
Lee, Albert S., Choe, Yoong-Kee, Matanovic, Ivana, & Kim, Yu Seung. The energetics of phosphoric acid interactions reveals a new acid loss mechanism. United States. doi:10.1039/C9TA01756A.
Lee, Albert S., Choe, Yoong-Kee, Matanovic, Ivana, and Kim, Yu Seung. Mon . "The energetics of phosphoric acid interactions reveals a new acid loss mechanism". United States. doi:10.1039/C9TA01756A.
@article{osti_1526963,
title = {The energetics of phosphoric acid interactions reveals a new acid loss mechanism},
author = {Lee, Albert S. and Choe, Yoong-Kee and Matanovic, Ivana and Kim, Yu Seung},
abstractNote = {Acid retention of phosphoric acid (PA)-doped proton exchange membranes (PEMs) is one of the critical factors that determine the durability of high temperature PEM fuel cells. However, the mechanism of PA loss in the PEMs in the presence of water is obscure in the context of the energetics of the PA cluster. Here, we study the energetics of PA-benzimidazole acid-base and biphosphate-ammonium ion pairs using density functional theory calculations and 31P NMR experiments to propose a novel PA loss mechanism. The results suggest that the removal of the PA from the membrane does not occur due to the strong interaction of PA-water, but due to the incapability of the base polymers to hold the water and PA beyond a certain level. Significantly higher interaction in the biphosphate-ammonium ion pair shifts the equilibrium PA composition in the PA cluster to higher values, which minimizes the PA loss in the presence of water. Introducing the high interaction with PA molecules provides a path for better PEM design that may allow using high temperature PEM fuel cells with excellent acid retention.},
doi = {10.1039/C9TA01756A},
journal = {Journal of Materials Chemistry. A},
number = 16,
volume = 7,
place = {United States},
year = {2019},
month = {3}
}

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Works referenced in this record:

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