High-performance AEM unitized regenerative fuel cell using Pt-pyrochlore as bifunctional oxygen electrocatalyst

The performance of fixed-gas unitized regenerative fuel cells (FG-URFCs) are limited by the bifunctional activity of the oxygen electrocatalyst. It is essential to have a good bifunctional oxygen electrocatalyst which can exhibit high activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this regard, Pt-Pb2Ru2O7-x is synthesized by depositing Pt on Pb2Ru2O7-x wherein Pt individually exhibits high ORR while Pb2Ru2O7-x shows high OER and moderate ORR activity. Pt-Pb2Ru2O7-x exhibits higher OER (eta(@10mAcm-2) = 0.25 +/- 0.01 V) and ORR (eta(@-3mAcm-2) = -0.31 +/- 0.02 V) activity in comparison to benchmark OER (IrO2, eta(@10mAcm-2) = 0.35 +/- 0.02 V) and ORR (Pt/C, eta(@-3mAcm-2) = -0.33 +/- 0.02 V) electrocatalysts, respectively. Pt-Pb2Ru2O7-x shows a lower bifunctionality index (eta(@10mAcm-2), OER - eta(@-3mAcm-2), ORR) of 0.56 V with more symmetric OER-ORR activity profile than both Pt (>1.0 V) and Pb2Ru2O7-x (0.69 V) making it more useful for the AEM (anion exchange membrane) URFC or metal-air battery applications. FG-URFC tested with Pt-Pb2Ru2O7-x and Pt/C as bifunctional oxygen electrocatalyst and bifunctional hydrogen electrocatalyst, respectively, yields a mass-specific current density of 715 +/- 11 A/g(cat)(-1) at 1.8 V and 56 +/- 2 A/g(cat)(-1) at 0.9 V under electrolyzer mode and fuel-cell mode, respectively. The FG-URFC shows a round-trip efficiency of 75% at 0.1 A/cm(-2), underlying improvement in AEM FG-UR FC electrocatalyst design.

Automated summary

The study focuses on the bifunctional oxygen electrocatalyst for fixed-gas unitized regenerative fuel cells (FG-URFCs), synthesizing Pt-Pb2Ru2O7-x which shows superior ORR and OER activity compared to benchmark electrocatalysts. It demonstrates potential for applications in AEM URFC or metal-air battery.