Evaluation of Speek |Chitosan As a Proton Exchange Membrane in Electrochemical Hydrogen Pumping

Abstract

In recent years, climate change has become more evident, requiring the use of renewable energy sources. In this context, energy conversion advanced technologies demand greater attention of the scientific and industrial community for the transition to the so-called "Global Hydrogen Economy" based on the hypothesis that hydrogen can play a role as an energy carrier [1] due its high energy content per unit weight.Proton Exchange Membrane Technology (PEM-Technology) responds to different industrial issues through different systems such as PEM-Electrolyser to produce hydrogen [2] or Electrochemical Hydrogen Pumping / Compression (EHP / EHC) to purify or compress hydrogen to finally distribute it [3–5].In our previously reported works, we prepared SPEEK-Chitosan blends, and we demonstrate with physicochemical characterization (SEM-EDS, TGA-DSC, Water Uptake, Proton Conductivity, etc.). This time we evaluated the best membrane blend S-CS 10%(SPEEK with a 80% of sulfonation degree and 10% of chitosan) in chronopotentiometry at different current density. The S-CS 10% membrane was compared with pristine SPEEK and Nafion115. Our membrane blend exhibited low cell voltage at high current density.In the Figure 1, results obtained via chronopotentiometry are shown for three different membranes for a continuous operating time of t = 1 h at T = 37.5 ° C and 100% RH. From this graph, the Nafion 115 membrane, when demanding a current density of j=1 A cm-2 loses stability and is not able to cover the demanded current; however, it shows some stability when the current demand decreases (j= 0.8 A cm-2). On the other hand, SPEEK and SQ 10% synthesized membranes present a better stability with demanding currents up to j=1 A cm-2 and j=1.3 A cm-2, respectively. The better performance of S-CS 10% is probably due to as there are sulfonic groups interacting with the protonated amine group, a Zwitterion effect is created, causing the water molecules to remain strongly trapped in the membrane by an electrostatic effect, preventing the membrane from dehydrating when working at higher current densities and therefore it consumes less energy [6]. Figure 1