Preparation And Performance Of Novel Tetraphenylphosphonium-Functionalized Polyphosphazene Membranes

Anion exchange membrane fuel cells (AEMFC) have attracted considerable attention owing to their high efficiency and low pollution levels. As an important part of AEMFC, the anion exchange membranes (AEMs) still faced some challenges such as the low ionic conductivity and poor alkaline stability. In order to solve these problems, several strategies for AEMs were designed by us and several types of highly qualified AEMs were prepared. The research content is as follows:1. Tetraphenylphosphonium-functionalized polyphosphazene (PPMPP-1) membranes in different IEC were synthesized. The fuel cell performance of PPMPP-1 membranes were explored. The results revealed that the highest OH- ionic conductivity was 20.5 mS·cm-1 in PPMPP-1-40 membrane at 80?.The ionic conductivity of PPMPP-1 membranes did not change obviously after immersion in 1 mol·L-1 KOH solution at 30? for 10 days.2. A series of tetraphenylphosphonium derivatives-functionalized polyphosphazene membranes (PPMPP-2, PPMPP-3 and PPMPP-4) were synthesized and characterized. The results revealed that the electron-donating effect of the substituents in the functionalized tetraphenylphosphonium cations correlated well with the ionic conductivity. The ionic conductivity order of the membranes studied in this work is PPMPP-3> PPMPP-4> PPMPP-2> PPMPP-1. Moreover, the alkaline stability were also consistent with the electron-donating effect. After 10 days ageing in 1 mol-L"1 KOH solution at 60? only 7.6% hydroxide conductivity degradation was observed in PPMPP-3.3. Novel hydrophilic crosslinked tetraphenylphosphonium derivatives-functionalized polyphosphazene membranes (PPMPP-5) were successfully synthesized. The IEC, WU, SR and electrochemical performance were explored. The properties of PPMPP-5 are greatly influenced by the cross-linking degree. The ionic conductivity of PPMPP-5 in the cross-linking degree of 60% is 27.9 mS·cm-1 at 80?. The properties of PPMPP-5 indicate these membranes are promising for the potential applications in AEMFCs.