Poly(arylene alkylene piperidinium)s for Anion Exchange Membrane Water Electrolyzers

Abstract

Anion exchange membrane (AEM) water electrolyzers have the potential to obviate the need for precious metal catalysts, and are therefore attracting an increasing attention.1 The high performance and durability of the device largely depend on the properties of the AEM with regards to hydroxide conductivity and resistance.2 ,3 The development of viable AEM candidates is continuously advancing. Recently, we reported on a series of poly(arylene alkylene piperidinium)s (PAAs) prepared from a ketone monomer specifically designed for high alkaline stability.4 The PAA AEMs reached high hydroxide conductivities, comparable with the state-of-the-art poly(arylene piperidinium)-based AEMs derived from piperidione, but showed significantly higher chemical stability under harsh alkaline conditions.5 In the present study, we have further developed PAA AEMs by copolymerizations to tune the ion exchange capacity (IEC). An AEM (PpTDMP-2.0) with an IEC of 2.0 mequiv.g−1 reached a high OH− conductivity of 129 mS cm−1 at 80 °C and a controlled water uptake of 80%. This AEM was selected for evaluated in an alkaline water electrolyzer fed with 1 M KOH at 70 °C. Using a novel noble-metal free NiFe layered double hydroxide (LDH) catalyst in the anode, initial results showed a high current density of 4.5 A cm−2 at 2.2 V. The corresponding performance of the state-of the-art Aemion+® membrane was measured for benchmarking, and the PAP AEM demonstrated a lower degradation rate from the beginning of the experiment. In the current presentation, we will further discuss the performance, system stability, and the prospects of PAA AEMs for use in electrolyzers and other electrochemical energy applications. C. Santoro, A. Lavacchi, P. Mustarelli, V. Di Noto, L. Elbaz, et al., ChemSusChem, 2022, 15, e202200027.D. Aili, M. R. Kraglund, S. C. Rajappan, D. Serhiichuk, Y. Xia, V. Deimede, J. Kallitsis, C. Bae, P. Jannasch, D. Henkensmeier, J. O. Jensen, ACS Energy Lett., 2023, 8, 1900–1910.E. J. Park, C. G. Arges, H. Xu and Y. S. Kim, ACS Energy Lett., 2022, 7, 3447-3457.D. Pan, P. M. Bakvand, T. H. Pham and P. Jannasch, J. Mater. Chem. A, 2022, 10, 16478-16489.J. S. Olsson, T. H. Pham and P. Jannasch, Adv. Funct. Mater., 2018, 28, 1702758. Figure 1. (a) Synthetic route and chemical structure of PpTDMP-2.0, (b) polarization curves of PpTDMP-2.0 and Aemion+ (left) after a constant current hold of 1 A cm-2 for 15 h (right). 5 cm² active area, 70 °C, 1 M KOH. Anode: 2.0 mgNiFe-LDH cm-2, Cathode 0.5 mgPt cm-2. Figure 1