Final Project Report for project titled "Fluoroalkylphosphonic-acid-based proton conductors"

Stephen Creager

关键词: COMPUTERS;    DESIGN;    ELECTROCHEMICAL ENERGY CONVERSION;    ELECTROLYTES;    ENERGY CONVERSION;    FUNCTIONALS;    HUMIDITY;    HYDROGEN FUEL CELLS;    MOLECULAR MODELS;    MOLECULAR STRUCTURE;    PHOSPHINIC ACIDS;    PHOSPHORIC ACID;    POLYMERS;    PROTON CONDUCTIVITY;    PROTON TRANSPORT;    PROTONS;    STORAGE;    TRANSPORT Hydrogen fuel cells;    electrolytes;    membranes;   

DOI  :  10.2172/1030791
RP-ID  :  GO16031_Clemson_2011_FinalReport_SEC6
PID  :  OSTI ID: 1030791
Others  :  TRN: US201202%%371

美国|英语

来源: SciTech Connect

【 摘 要 】

The overall objective of this research was to create new proton-conducting polymer electrolytes for use in energy conversion devices including hydrogen fuel cells that could operate at high temperatures (95-130 C) and under low relative humidity (< 50% RH) conditions. The new polymers were based on the fluoroalkylphosphonic and phosphinic acid (FPA) groups (see illustration below) which offer prospects for rapid proton transport by a proton-hopping mechanism similar to that which operates in phosphoric acid, a well-known proton-transporting electrolyte that is used in a class of hydrogen fuel cells that work well under the conditions noted above and are already commercially successful. The two specific project objectives were as follows: (1) synthesize and characterize new proton-conducting electrolytes based on the fluoroalkylphosphonic and phosphinic acid (FPA) functional groups; and (2) create and apply new computer models to study protonic conduction in FPA-based electrolytes. The project was successful in creating the desired polymer electrolytes and also a series of molecular model compounds which were used to study proton transport in FPA electrolytes in general. Computer models were created to study both structure and proton-transport dynamics in the electrolytes, particularly the molecular model compounds. Rapid proton transport by a hopping mechanism was found in many of the model compounds and correlations with transport rates with molecular structure were identified. Several polymeric analogs of FPA model compounds were prepared and studied, however FPA-based polymeric materials having very high protonic conductivities under either wet or dry conditions were not obtained. Several possible reasons for the failure of polymeric materials to exhibit the expected high protonic conductivities were identified, including a failure of the polymers to adopt the phase-separated secondary structure/morphology necessary for high proton conductivity, and an unexpected polymer crosslinking effect of acidic groups having two P-OH groups. The project has lent insight into how FPA groups transport protons in both liquid and polymeric forms, which provides guidance to future efforts to design and prepare future generations of proton-conducting polymer electrolytes for hydrogen fuel cells and other types of electrochemical energy conversion and storage devices.