Enhanced Activity and Stability of Nanoporous PtIr Electrocatalysts for Unitized Regenerative Fuel Cell

Abstract

The unitized regenerative fuel cell (URFC) is a useful electrochemical energy conversion/storage device, in which catalysts for the dual-function (oxygen reduction reaction, ORR, and oxygen evolution reaction, OER) electrodes of URFCs must be operative over a wide range of potentials. Herein, we report a highly active and stable bifunctional electrocatalyst, a three-dimensionally interconnected nanoporous PtIr thin film (np-PtIr) for URFC, which was prepared by an electrochemical selective leaching of a less noble element, Os. The np-PtIr showed a much enhanced URFC performance, such as an about 21% and 485% higher round-trip efficiency than that of sole Pt and Ir, respectively, and much enhanced stability confirmed with the ICP-OES analyses. It was revealed from various electrochemical tests and XPS studies that the enhanced URFC performance of np-PtIr resulted from a significantly increased surface area due to the formation of a three-dimensionally interconnected nanoporous structure, as well as a minimization of the ohmic loss due to an inner metallic conduction paths.