PNNL

Abstract

Direct ethanol fuel cells (DEFCs) operated in alkaline solutions have been widely investigated as nontoxic and low-corrosive energy conversion devices with high energy and power densities using easily portable liquid fuels. However, in the current practice, the lack of highly active, stable, low-cost electrocatalysts hinders the scalable commercialization of DEFCs. In this work, a new design strategy based on catalytic tri-synergism is discovered for high-performance DEFCs. Specifically, ultrafine Pd nanoparticles/clusters were decorated on the surface of nitrogen-doped highly graphitic carbon with cobalt nanoparticles in the cores (Pd/N-C@Co) for bifunctional ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR). The catalytic tri-synergism, including the spatial confinement effect between Co and N-C, the electronic effect between Pd and Co, and the support effect between Pd and N-C@Co, endows the Pd/N-C@Co with a kinetically facilitated C1-12e pathway for complete EOR. As a result, the Pd/N-C@Co delivers mass activities of 7.05 A mg-1Pd and 0.94 A mg-1Pd towards EOR and ORR, respectively, far surpassing the commercial Pd/C and Pt/C. Besides, about 80.5% of the initial ORR activity can be retained after 30000 cycles. A maximum power density of 1.1 W mg-1Pd is achieved in actual DEFCs, which is 7.5 times and 4.0 times higher than those of Pd/C and Pt/C, respectively. This work presents a new catalyst strategy for practical DEFCs, which will promote the development and research of clean energy.