Fabrication Of Proton Transport Channels And Intensification Of Membrane Performance Based On Donor-acceptor Groups

Proton exchange membrane fuel cell?PEMFC?has become one of the most promising new power generation devices due to its high energy density,environment-friendly feature,low noise,quickly start-up,easy integration,etc.As the key part of the PEMFC,proton exchange membrane?PEM?determines the output power of fuel cells directly.Developing PEM materials with high proton conductivity,low fuel permeability and high stability is vital to the large-scale application of PEMFC.This study is guided by the biomimetic and bio-inspired theory,the strategy is to build the highly efficient proton-transfer channel.The research starts from multi-level structure such as membrane matrix,hybrid interface,transfer channel,etc to fabricate new type proton-transfer sites.The physical and chemical microenvironment are optimized,both the Vehicle and Grotthuss mechanisms are adjusted to achieve high proton conductivity under high temperature and low humidity,to solve the tradeoff effect between proton conductivity and methanol permeability.The details are summarized as follows:Fabrication of highly efficient proton-transfer channel based on single donor-acceptor groups?phosphoric acid groups?:?i?ATP molecules are introduced into the polymer matrix by solution blending to prepare composite membrane.The introduction of numerous phosphoric acid groups increases the water absorption of the membrane and enhances the proton conductivity;?ii?The phosphoric acid molecules are firmly loaded into pores of COF materials via vacuum-assisted method and then introduced into Nafion polymer to prepare composite membranes.Phosphoric acid-loaded COF enhances the continuity of proton transport channels and reduces the proton transfer energy barrier significantly.The maximum power density of the single cell of Nafion/H₃PO₄@S1-15 composite membrane is 60.3%higher than that of recast Nafion.Fabrication of highly efficient proton-transfer channel based on binary donor-acceptor groups?acid-base groups?:?i?The histidine-functionalized GO is introduced into SPEEK polymer to prepare hybrid membranes.The acid-base pairs formed between two-dimensional lamellae and polymer provide highly efficient proton-transfer channels,at the same time,the methanol permeability is significantly reduced.The selectivity of SPEEK/GO-his-4 is⁵ times higher than that of the pure SPEEK membrane,much higher than that of the Nafion^?117 membrane;?ii?Hollow mesoporous silica?HMS?microspheres functionalized by three different acid-base pairs are prepared,then introduced into Nafion polymer to prepare hybrid membrane and study the effect of acid-base pair types on the proton transfer process.The HMS plays a similar role as“water reservoirs”in the membrane,optimizing the water environment in the membrane.The binary donor-acceptor system is formed between amino acid molecules grafted on HMS and–SO₃H groups in Nafion,optimizing the Vehicle and Grotthuss mechanisms simultaneously;?iii?The functionalized SiO₂-TiO₂binary nanoparticles with tunable ratio of acid to base are synthesized by"one-pot"method,then introduced into Nafion polymer to prepare hybrid membrane and study the effect of acid-base ratio on the proton transfer process.The synergistic effect between the–SO₃H groups and–NH₂ groups increases the proton conductivity significantly.The proton conductivity of Nafion/Si1-Ti2-160 hybrid membrane is increased by two orders of magnitude compared with recast Nafion membrane at80°C and 26%RH.