Structural Regulation And Proton Conductivity Of Organosilicon Polymers

Solid-state proton conductor with high conductivity that operate under wide temperature range and low humidity conditions can be used in the fuel cell vehicles to solve the problems that proton exchange membranes in fuel cells can not start at low temperature,can not reach high temperature to prevent catalyst CO poisoning and proton conductivity decreased sharply in low humidity environment due to the narrow operating temperature range and high humidity dependence.At present,proton conductors can be divided into two categories:(1)proton-conducting under humidity,which can impart or improve proton conductivity under humidity conditions,but the humidification requirement also raises some critical issues,the high humidity reliance and narrow operating temperature window;(2)anhydrous proton-conducting broaden their operating temperature range by water analogs(such as azoles and organic hydroxyl compounds)as proton sources,but their proton conductivity is obviously lower than those at humidity conditions.To address these issues,the hydrothermal chemical stability of Periodic Mesoporous Organosilicas(PMOs)is used as the parent materials to synthesize high performance prton conducting materials.On the one hand,PMOs with different pore sizes were controlled by different organosilicon precursors under the action of structure directing agent,and then the sulfonate was introduced into the pore walls by sulfonation to obtain functionalized PMOs(s-PMO-1 and s-PMO-2).The obtained s-PMO-2 material shows better selective adsorption and separation ability for C2H2/CH4 mixture.Two imidazole-loade proton conductors(Im@PMO-2 and Im@s-PMO-2)were obtained by loading imidazole into PMO-2 and its sulfonated derivative s-PMO-2.With the acid-base pairs,the resulting material Im@s-PMO-2 shows efficient proton conductivity over temperature range from-40?(1.12×10-6 S/cm)to 180?(7.11×10-3 S/cm)under anhydrous conditions.On the other hand,to obtain high performance proton conductor under low humidity conditions,the structure-directing agents with different chain lengths were used to control the PMOs with different Vmesopore/Vmicropore ratio,hydrophilic polyaniline(PANI)was introduced into the stable and ordered channels of PMOs,and high proton conductors(PANI@PMO-2)were constructed at wide temperature range and low humidity.PANI@PMO-2 shows efficient proton conductivity over temperature range from(7.19× 10-3 S cm-1)to 130?(4.38×10-2 S cm-1)under anhydrous conditions and 4.38×10-2 S cm-1 at 80?and 95%RH,and its humidity dependence is only 0.005,which is much lower than the commercial Nafion 212(0.01).In addition,for the microcrystalline PMOs cannot know the assembly process of organosilicon polymerization from the structure,we synthesized a series of metal siloxane single crystals with polyphenylsiloxane that is also polymerized by Si-O bond as a ligand and metal salt.The effects of changes in the external environment(temperature,reactants,etc)and substituents on the assembly of organosilicon polymers were explored by single crystal X-ray diffraction,aiming to provide new ideas for designing and fabricating high performance organosilicon-based polymers.