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@ARTICLE{Bostrm:1016955,
      author       = {Boström, Oskar and Choi, Seung-Young and Xia, Lu and
                      Meital, Shviro and Lohmann-Richters, Felix and Jannasch,
                      Patric},
      title        = {{A}lkali-stable polybenzimidazole anion exchange membranes
                      tethered with {N} , {N} -dimethylpiperidinium cations for
                      dilute aqueous {KOH} fed water electrolyzers},
      journal      = {Journal of materials chemistry / A},
      volume       = {11},
      number       = {39},
      issn         = {2050-7488},
      address      = {London ˜[u.a.]œ},
      publisher    = {RSC},
      reportid     = {FZJ-2023-03863},
      pages        = {21170 - 21182},
      year         = {2023},
      abstract     = {Polybenzimidazole (PBI) is currently considered as a
                      membrane material for alkaline water electrolyzers (AWEs),
                      and has to be fed with highly concentrated aqueous KOH
                      electrolytes in order to ensure sufficient electrolyte
                      uptake and conductivity. However, the harsh operating
                      conditions significantly limit the lifetime of PBI
                      membranes. In response, we here report on the synthesis and
                      performance of a series of PBI membranes tethered with
                      alkali-stable mono-piperidinium (monoPip) and
                      bis-piperidinium (bisPip) side groups, respectively, which
                      allows the use of more dilute KOH concentrations. The
                      electrolyte uptake of these membranes was found to be
                      inversely proportional to the electrolyte concentration,
                      which was in stark contrast to pristine PBI membranes. The
                      high electrolyte uptake at low concentrations by the present
                      membranes enables operation of AEMWE systems fed with dilute
                      electrolytes, which significantly decrease membrane
                      degradation. After immersion in 2 M aqueous KOH at 80 °C
                      for up to 6 months, no degradation was detected by 1H NMR
                      spectroscopy in the monoPip series of AEMs, and a mere $7\%$
                      ionic loss by Hofmann elimination in the bisPip series.
                      Membranes tethered with bisPip groups produced the best
                      AEMWE performance, and a sample with a hydroxide ion
                      exchange capacity of 2.4 meq. g−1 reached a high current
                      density of 358 mA cm−2 at 2 V with demonstrated stability
                      over 100 h, using 2 M aqueous KOH and only simple nickel
                      foam electrodes. This is comparable to the performance
                      reported for Zirfon diaphragms and pristine PBI membranes
                      operating with much higher concentrations of KOH in the
                      range of 5–7 M. The low KOH concentration of the present
                      membranes brings important advantages for the material
                      stability in the cell, as well as for the balance of plant,
                      and the results provide useful insights into the molecular
                      design of AEMs for dilute electrolyte-fed AEMWE systems.},
      cin          = {IEK-14},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IEK-14-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001077204700001},
      doi          = {10.1039/D3TA03216G},
      url          = {https://juser.fz-juelich.de/record/1016955},
}