Low Pt loading for high-performance fuel cell electrodes enabled by hydrogen-bonding microporous polymer binders

A key challenge for fuel cells based on phosphoric acid doped polybenzimidazole membranes is the high Pt loading, which is required due to the low electrode performance owing to the poor mass transport and severe Pt poisoning via acid absorption on the Pt surface. Herein, these issues are well addressed by design and synthesis of effective catalyst binders based on polymers of intrinsic microporosity (PIMs) with strong hydrogen-bonding functionalities which improve phosphoric acid binding energy, and thus preferably uphold phosphoric acid in the vicinity of Pt catalyst particles to mitigate the adsorption of phosphoric acid on the Pt surface. With combination of the highly mass transport microporosity, strong hydrogen-bonds and high phosphoric acid binding energy, the tetrazole functionalized PIM binder enables an H-2-O-2 cell to reach a high Pt-mass specific peak power density of 3.8W mg(Pt)(-1) at 160 degrees C with a low Pt loading of only 0.15 mg(Pt) cm(-2). Lowering the Pt loading while maintaining high fuel-cell performance is an important but difficult task. Here the authors report modified polymers with intrinsic microporosity as binder for preferential retention of phosphoric acid in the catalyst layer, which offers great opportunities to lower the catalyst loading for high-temperature proton exchange membrane fuel cell.

Automated summary

The use of catalyst binders based on polymers of intrinsic microporosity has addressed the challenges faced by phosphoric acid doped polybenzimidazole membranes fuel cells, achieving low Pt loading and high fuel cell performance.