Good question, But i think still much more research is necessary to reduce the IR in fuel cell operations. According to my knowledge peoples were trying for this even in India in the area of microbial fuel cell technology. All the best.
Rite chandu.. now research is on micro and nano level MFC where the IR could be reduce at the possible extent.. and then such micro MFCs are integrated resulting in amplified O/P... hopefully...
As far as I think, through series-parallel connection of electrodes the problem of internal resistance can be confronted somewhat because connecting in series will add up the voltage and simultaneously parallel connection will increase the current keeping the resistance constant.
low external resistance values also result in low internal resistance values from ohms law. Biofilm thickness is also suggested as a factor. factors that favor biofilm formation eg low external resistances are useful
Microbial Fuel Cell operated with lower external resistance leads to steady increment in dynamic capacities of the biocatalyst with continuous current generation.
Internal resistance is inversely proportional to performance. Therefore, if you want to record or observe significant results, pay attention to electrode material and surface area, the conductivity of electrolytes, reactor volume, orientation vs inter-electrode distance. Of course, there are other factors, but these are key.