Study On The Delamination Of Layered Double Hydroxides And Their Use In Anionic Exchange Membrane

Alkaline anion exchange membrane fuel cell?AAEMFC?is considered as one of the most promising fuel cell by virtue of its low working temperature,high power density,fast start-up and zero emissions.As the core component of alkaline anion exchange membrane fuel cell,anion exchange membrane?AEM?performance is directly related to the comprehensive performance of the fuel cell.However,the current anion exchange membrane has been faced with the problems of low conductivity,poor stability,complex synthesis route and so on,which can not meet the needs of the practical application of fuel cell.Therefore,it is important to find an anion exchange membrane with high conductivity,high stability and simple synthesis route.In this paper,for the first time,we have delaminated the layered double hydroxides?LDHs?in an aqueous system by a novel freeze-thaw method.The freeze-thaw was carried out with cycles of freezing the layered double hydroxide solution in liquid nitrogen and subsequent melting the frozen solution in a 80?water bath.Around 67%LDHs were delaminated into nanosheets after 16freeze-thraw cycles.Compared with delamination in formamide under sonication,the method used for the preparation of layered double hydroxides nanosheets?LNS?was shorter,and LNS'lateral size was larger,which will help to construct a good mechanical strength layered double hydroxides nanosheets anion exchange membrane?LNS AEM?.In order to avoid the decrease of the lateral size of layered double hydroxides nanosheets by ultrasound,the Co-Al-Cl LDHs was exfoliated in formamide by stirring-assisted.The Co-Al-Cl LNS AEM was prepared for the first time.The results show that Co-Al-Cl LNS AEM has strong thermal stability and higher conductivity than Co-Al-Cl LDHs AEM.The ion conductivity of Co-Al-Cl LNS AEM was 5.47mS/cm at 80?,which improved by an order of magnitudes compared to Co-Al-Cl LDHs AEM.Using green and pollution-free water as solvent,we successfully prepared Co-Al-NO₃ LNS by the first step of synthesizing LDHs precursor and the second step of hydrothermal delamination.Co-Al-NO₃ LDHs AEM and Co-Al-NO₃ LNS AEM were prepared by the filtration process.The experimental results show that Co-Al-NO₃ LNS AEM has good stability.Compared to Co-Al-NO₃ LDHs AEM,Co-Al-NO₃ LNS AEM has better conductivity.The ion conductivity of Co-Al-NO₃LNS AEM reached 6.1 m S/cm at 80?,Which was 8-fold higher than that of the Co-Al-NO₃ LDHs AEM.