Nanophase-Engineered Bifunctional Catalysts for Oxygen Electrodes in High-Performance Unitized Regenerative Fuel Cells

Abstract

The development of highly efficient and durable bifunctional oxygen catalysts for high-performance unitized regenerative fuel cells (URFCs) is crucial for their practical application. Herein, the nanophase-separated ultrafine PtCoW alloy and the Ir nanocrystals covalently coupled with carbon were prepared by using a strawberry-like Ir/C hybrid as a structure-oriented template. The resultant Pt-based ternary alloy and the IrO2-covered metallic Ir feature a well-defined nanophase-separated structure with double active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In acidic environments, the bifunctional catalysts exhibit a total overpotential difference of 585 mV, showing much higher activity and stability compared with commercial Pt/C and IrO2. The outstanding bifunctional performance can be attributed to the strong particle-to-particle interaction between PtCoW and the neighboring Ir in their composite. Density functional theory calculations further confirm that the formed IrO2(100)∥Ir­(111) epitaxial structure can lower the binding energy of reaction intermediates, thus improving OER kinetics. Moreover, the downshifted d-band center of Pt and the compressive strain in PtCoW alloy should be responsible for the remarkably enhanced ORR activity. Therefore, this work may contribute to URFC systems used as safe and efficient energy storage and conversion devices for space flights, vehicles, and stations.

Bifunctional Electrode Design Targeting Co‐Enhanced Kinetics and Mass Transport for Hydrogen and Water Oxidation Reactions

“…Bifunctional electrodes are essential for integrating the functionalities of two different energy-conversion devices into a single system, which can lower capital cost, volume, and weight compared to the operation of each device separately. [1][2][3][4] Among the various DOI: 10.1002/adfm.202302586 systems requiring bifunctional electrodes, hydrogen/oxygen oxidation/reduction reactions have high priority for achieving lowcarbon or hydrogen-based energy systems. There are representative catalytic elements suitable for each reaction.…”

Tailoring the Mass Transport to Achieve High-Performing Unitized Regenerative Fuel Cells Considering Practical Operating Conditions

“…S1. Current research efforts have been primarily focused on developing bifunctional catalysts to advance ORR/OER kinetics, [16][17][18][19][20][21][22][23] however, less on the necessity to tailor mass transport when O 2 and water transport are required to share the same diffusion media under CG mode operation. The oxygen electrode in a URFC device shares similar components with the anode (OER electrode) used in a water electrolyzer, which typically consists of a titanium-based porous transport layer (PTL) to avoid corrosion instead of a carbon-based gas diffusion layer (GDL) used in a fuel cell.…”