Gas Separation and Gas Sensor Properties of Zinc-based Nanocomposite Materials

Author:Liu Di

Supervisor:pang guang sheng


Degree Year:2019





Now,the design and synthesis of composite materials based on nanomaterials represents a very important research direction in this field.ZIF-8 nanoparticles and ZnO nanoparticles,as representative of zinc-based nanomaterials,have potential application in gas separation and gas sensor due to their advantages of easy synthesis,cheapness,good stability and high performance.In this paper,preparation of ZIF-8(zeolitic imidazolate framework-8)/GO(graphene oxide)composite membrane,Au@ZnO nanoparticles,and their performance in gas separation and gas sensor are studied.The details are as follows:1.Setup of the gas separation test instrumentMembrane separation has attracted much attention because of its efficient and energy-saving separation method.However,the membrane separation performance needs to be measured accurately.To achieve this purpose,we setup an instrument to measure the separation performance of the gas separation membrane according to the membrane permeability mechanism.2.GO/ZIF-8 membrane for H2/CH4 gas separationGas separation membrane has attracted a great deal of interest due to its wide application in industry for centuries.However,it still remains great challenge for acquiring a gas separation membrane with both high separation efficiency and good permeability in large quantity.Herein,a layered composite,which is consisted of ZIF-8 nanocrystals and GO nanosheets with the aid of polyethyleneimine(PEI)polyelectrolytes,is facilely and massively produced and used as gas separation membrane.The uniform ultrathin nature of the ZIF-8-PEI-GO composite membrane(ca.400 nm in thickness)is beneficial for easy gas permeation,while the window size effect originated from the ZIF-8 nanocrystals and the long gas diffusion channels constructed by GO nanosheets together endow the membranes excellent gas selectivity.In H2/CH4 separation,the composite membrane exhibits excellent selectivity of 43 while the permeance reaches 6.3*10-8 mol m-2 s-1 Pa-1.This work will open the avenue towards development of next generation gas separation membrane by rational structural design of composite structures.3.Mesoporous Au@ZnO nanostructure for formaldehyde sensing performanceThe Au@ZnO core-shell nanostructures are successfully prepared by a facile hydrothermal method,and their gas-sensing property is studied.The obtained Au@ZnO nanostructures have uniform size of ca.170 nm and are characteristic of one Au nanoparticle(diameter ca.32 nm),which are surrounded by a mesoporous ZnO shell outside.Impressively,when used as the sensors,the Au@ZnO core-shell nanostructures exhibit high sensitivity and remarkable selectivity toward HCHO.Compared with bare ZnO nanoparticles,the response value of the Au@ZnO core-shell nanostructures toward 100 ppm HCHO at 220°C is more than five times higher(45.28 vs.8.86).An investigation in details reveals that the Au nanoparticle cores contribute to both the improved response originated from Schottky barrier formation and the high selectivity resulted from their catalytic effect.