High-performance of polyaromatic alkaline membrane fuel cells was achieved with a polyfluorene ionomer with minimizing adsorption on hydrogen oxidation catalysts.

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1Cation exchange membranes (CEMs) have attracted tremendous attention in electrochemical 2 energy conversion and storage systems owing to their high proton conductivity and chemical 3 stability. However, applications of CEMs suffer from a number of disadvantages such as 4 requirement of costly platinum catalyst, and high crossover of fuels or positively charged redox 5 species due to the electro-osmotic drag. Anion exchange membranes (AEMs) have shown 6 promising characteristics to overcome some of the problems associated with CEMs; the 7 advantages of AEMs being selective transport anionic charge carriers, lower crossover of 8 cationic redox couples, and facile reaction kinetics in energy conversion processes. These unique 9 properties of AEMs result mainly from the density and distribution of positively charged 10 functional groups, along with a macromolecular polymer backbone. As a result, there has been 11 an increasing demand for the development of AEMs with better selectivity, higher chemical 12 stability and conductivity, and a lot of work have been carried out in this area. The aim of this 13 review is to discuss developments in the synthesis and applications of AEMs in the field of 14 electrochemical energy conversion and storage, on which many researchers are working in recent 15 years. 16 2 for sustainable energy sources, and the need for energy security have forced the migration from 3 hydrocarbon based fossil fuels to renewable and environmentally friendly energy sources. 1 Also, 4 an increased awareness of the environmental issues along with a potential energy shortage has 5 led to accelerated research efforts in energy conversion and storage. Distributed power 6 generation systems based on fuel cells are expected to be an important power source in the future 7 due to their advantages, such as attractive efficiency, low carbon emission, and flexible 8 operations. 2 However, their inherent characteristics such as a long start-up time and poor 9 response to immediate power demands are major obstacles for the commercialization of such 10 systems. Therefore, hybrid distributed power systems based on fuel cells and batteries are 11 introduced, in order to best utilize the individual characteristics of each device. 3,4 Most 12 electrochemical conversion and storage systems such as fuel cells and redox flow batteries are 13 dependent on ion exchange membranes (IEMs). 5-7 These devices can work only if the IEM 14 separates the anode and the cathode chambers and mediate the conducting ions (e.g., protons and 15 hydroxide ions) for the electrochemical reactions in the system. Apart from good conducting 16 properties, some other requirements such as crossover and chemical stability are major concerns 17 in the development of IEMs. 8,9 18 Polymer electrolyte membrane fuel cells (PEMFC) 19 While fuel cells were invented in 1839 by Sir William Grove, their first practical use was 20 reported only in the 1950s in the NASA Apollo space program. 10 Over the past two decades, fuel 21 cell research has gained pace due...