MOF-Derived Bimetallic Pd–Co Alkaline ORR Electrocatalysts

Abstract

The development of highly active, durable, and low-cost electrocatalysts for the oxygen reduction reaction (ORR) has been of paramount importance for advancing and commercializing fuel cell technologies. Here, we report on a novel family of Pd-Co binary alloys (Pd_xCo, x = 1-6) embedded in bimetallic organic framework (BMOF)-derived polyhedral carbon supports. BMOF-derived Pd₃Co, annealed at 300-400 °C, exhibited the most promising ORR activity among the family of materials studied, with a half-wave potential (E_1/2) of 0.977 V vs RHE and a mass activity of 0.86 mA/μg_Pd in 1 M KOH, both values being superior to those of commercial Pd/C electrocatalysts. Moreover, it maintained robust durability after 20,000 potential cycles with a minimal degradation in E_1/2 of 10 mV. The enhanced performance and stability are ascribed to the uniform elemental distribution of Pd and Co and the Co-containing N-doped carbon (Co-N-C) structures. In anion exchange membrane fuel cell (AEMFC) tests, the peak power density of the cell employing a BMOF-derived Pd₃Co cathode reached 1.1 W/cm² at an ultralow Pd loading of 0.04 mg_Pd/cm². Strategies developed herein provide promising insights into the rational design and synthesis of highly active and durable ORR electrocatalysts for alkaline fuel cells.