High-performance AEM unitized regenerative fuel cell using Pt-pyrochlore as bifunctional oxygen electrocatalyst.
basic_science · Level V
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- Record sourced from PubMed, PMID 34593643.
- Also identified by DOI 10.1073/pnas.2107205118 and PMC identifier 8501831.
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Abstract
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-Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> is synthesized by depositing Pt on Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> wherein Pt individually exhibits high ORR while Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> shows high OER and moderate ORR activity. Pt-Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> exhibits higher OER (η<sub>@10mAcm-2</sub> = 0.25 ± 0.01 V) and ORR (η<sub>@-3mAcm-2</sub> = -0.31 ± 0.02 V) activity in comparison to benchmark OER (IrO<sub>2</sub>, η<sub>@10mAcm-2</sub> = 0.35 ± 0.02 V) and ORR (Pt/C, η<sub>@-3mAcm-2</sub> = -0.33 ± 0.02 V) electrocatalysts, respectively. Pt-Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> shows a lower bifunctionality index (η<sub>@10mAcm-2, OER</sub><sup>-</sup> η<sub>@-3mAcm-2, ORR</sub>) of 0.56 V with more symmetric OER-ORR activity profile than both Pt (>1.0 V) and Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> (0.69 V) making it more useful for the AEM (anion exchange membrane) URFC or metal-air battery applications. FG-URFC tested with Pt-Pb<sub>2</sub>Ru<sub>2</sub>O<sub>7-x</sub> and Pt/C as bifunctional oxygen electrocatalyst and bifunctional hydrogen electrocatalyst, respectively, yields a mass-specific current density of 715 ± 11 A/g<sub>cat</sub><sup>-1</sup> at 1.8 V and 56 ± 2 A/g<sub>cat</sub><sup>-1</sup> 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<sup>-2</sup>, underlying improvement in AEM FG-URFC electrocatalyst design.