The disadvantage of anion ionomer that possesses low hydroxide conductivity, and thermal and chemical instability hinders the development of the high-performance anion-exchange membrane direct liquid fuel cells. Instead of adding additional base and synthesizing high-conductivity ionomer material, by gaining insight into species transports, herein, we propose an anion-ionomer-free anion-exchange membrane direct formate fuel cell (AEM DFFC). Experimental result reveals that this conceptual anion-ionomer-free AEM DFFC can operate stably within a 6-h constant-current discharge at 10 mA cm −2 , mainly because formate hydrolysis renders a high OH − conductivity. It was also found that the anion-ionomer-free AEM DFFC yields a peak power density as high as 41 mW cm −2 at 40 °C, 40% higher than that of the conventional quaternary ammonia polysulfone anion-ionomer AEM DFFC. This can be attributed to the fact that the OH − -containing formate solution facilitates the mass and charge transports, thereby enlarging the triple-phase boundary for both anodic formate oxidation reaction and cathodic oxygen reduction reaction .
Kuibo Zhang,Shoutao Gong,Baolin Zhao,Yanxiang Liu,Naeem Akhtar Qaisrani,Lingdong Li,Fengxiang Zhang,Gaohong He
Inadequate hydroxide conductivity of anion exchange membrane (AEM) is one of the obstacles restricting practical application of anion exchange membrane fuel cell. In this work, we report the design, fabrication and properties of AEMs based on bent-twisted non-coplanar block copolymer . The bent-twisted polymer backbone creates high free volume size so that hydroxide ion transport is facilitated. The free-volume effect can also facilitate microphase separation due to enhanced chain segment motion. With the free-volume holes working synergistically with microphase-separation enabled ion channels, the membrane showed a high conductivity (35 mS cm −1 at room temperature) at a relatively low ion exchange capacity (IEC, 1.25 meq g −1 ); it also exhibited a good dimension stability, the swelling ratio being 4.7% at room temperature and kept virtually unchanged with temperature because of relatively low IEC. A H 2 /O 2 fuel cell employing the fabricated AEM yielded a high power density (262 mW cm −2 at 50 °C). Our work opens up a new route to fabrication of highly conductive AEM with relatively low IEC.
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