Preparation And Water Electrolysis Properties Of Polyaryl Piperidine Alkaline Membrane

Hydroxide ion exchange membrane（HEM）is one of the core components of electrolytic cell,which is composed of polymer backbone and cationic groups.The action of HEM transfers OH^-ions from the cathode side to the anode side;As a diaphragm separates the gas generated from the two poles.The structure of the polymer skeleton and the distribution of cationic groups in the polymer system,which will affect the alkalinity resistance of HEM.It is common knowledge that the presence of aryl ether bonds in the polymer backbone will be attacked by OH^-,and limit its long-term use in alkaline electrolytic cells.In this paper,a polyarpiperidine polymer without aryl ether bond is prepared,which reduces the possibility of degradation of the polymer backbone and makes the polymer have good alkali stability.Meanwhile,the main chain polymer contains three monomers,and partial quaternization can achieve precise control of the ion exchange capacity（IEC）.First,the polyarpiperidine polymer is synthesized by super acid-catalyzed reaction of terphenyl,N-methyl-4-piperidone and methyl pyruvate,and then functionalized with methyl iodide to obtain QPpi-Co-Pmp membrane.The OH^-ion conductivity of QPpi-Co-Pmp-90%membrane is 44 m S cm^-1 at 30℃.The membrane is immersed in 1 M KOH at 80℃for 552 h,and the conductivity can remain 89%of the initial value,indicating that the membrane has good alkali resistance;Using QPpi-Co-Pmp-90%membrane as the cell separator,the cell current density reaches 555 m A cm^-2 at 1.9 V under 1 M KOH and 80°C.The durability is tested at 0.4A cm^-2,and cell run time has more than 1200 h.The voltage is stable at 2.0 V,showing excellent electrochemical durability.To improve the hydroxide ion conductivity of the membrane,increase the cationic groups while reducing the degree of functionalization,by introducing flexible long side chains into the polymer backbone to achieve a balance between high ionic conductivity and low swelling.A piperidine type dicationic membrane（QPpi-6C）is synthesized.The OH^-ion conductivity of QPpi-6C-60%membrane is 48 m S cm^-1 at 30℃;The cell current density reaches 652 m A cm^-2at 1.9 V under 1 M KOH and 80℃;The durability is tested at 0.4 A cm^-2,cell run time has more than 260 h and the voltage is stable at 1.98 V,showing excellent electrochemical performance.