Nitrogen-doped Carbon-CoOx Nanohybrids: A Precious Metal Free Cathode that Exceeds 1.0 W cm-2 Peak Power and 100 h Life in Anion-Exchange Membrane Fuel Cells.

ABSTRACT: Efficient and durable nonprecious metal electrocatalysts for the oxygen reduction (ORR) are highly desirable for several electrochemical devices, including anion exchange membrane fuel cells (AEMFCs). Here, a 2D planar electrocatalyst with CoOx embedded in nitrogen-doped graphitic carbon (N-C-CoOx ) was created through the direct pyrolysis of a metal-organic complex with a NaCl template. The N-C-CoOx catalyst showed high ORR activity, indicated by excellent half-wave (0.84 V vs. RHE) and onset (1.01 V vs. RHE) potentials. This high intrinsic activity was also observed in operating AEMFCs where the kinetic current was 100 mA cm-2 at 0.85 V. When paired with a radiation-grafted ETFE powder ionomer, the N-C-CoOx AEMFC cathode was able to achieve extremely high peak power density (1.05 W cm-2 ) and mass transport limited current (3 A cm-2 ) for a precious metal free electrode. The N-C-CoOx cathode also showed good stability over 100 hours of operation with a voltage decay of only 15 % at 600 mA cm-2 under H2 /air (CO2 -free) reacting gas feeds. The N-C-CoOx cathode catalyst was also paired with a very low loading PtRu/C anode catalyst, to create AEMFCs with a total PGM loading of only 0.10 mgPt-Ru  cm-2 capable of achieving 7.4 W mg-1 PGM as well as supporting a current of 0.7 A cm-2 at 0.6 V with H2 /air (CO2 free)-creating a cell that was able to meet the 2019 U.S. Department of Energy initial performance target of 0.6 V at 0.6 A cm-2 under H2 /air with a PGM loading <0.125 mg cm-2 with AEMFCs for the first time.

SUBMITTER: Peng X 

PROVIDER: S-EPMC6468319 | biostudies-other | 2019 Jan

REPOSITORIES: biostudies-other