Effect of ZIF-8 Crystal Size on the O2 Electro-Reduction Performance of Pyrolyzed Fe–N–C Catalysts

Catalysts

Vanessa Armel²  Julien Hannauer²  Frຝéric Jaouen¹ 

[1] Institut Charles Gerhardt Montpellier UMR 5253, CNRS, Université de Montpellier, 34095 Montpellier Cedex 5, France;

关键词: metal organic framework;    electrocatalysis;    fuel cell;    oxygen reduction;    non precious metal;    templating;   

DOI  :  10.3390/catal5031333

来源: mdpi

【 摘 要 】

The effect of ZIF-8 crystal size on the morphology and performance of Fe–N–C catalysts synthesized via the pyrolysis of a ferrous salt, phenanthroline and the metal-organic framework ZIF-8 is investigated in detail. Various ZIF-8 samples with average crystal size ranging from 100 to 1600 nm were prepared. The process parameters allowing a templating effect after argon pyrolysis were investigated. It is shown that the milling speed, used to prepare catalyst precursors, and the heating mode, used for pyrolysis, are critical factors for templating nano-ZIFs into nano-sized Fe–N–C particles with open porosity. Templating could be achieved when combining a reduced milling speed with a ramped heating mode. For templated Fe–N–C materials, the performance and activity improved with decreased ZIF-8 crystal size. With the Fe–N–C catalyst templated from the smallest ZIF-8 crystals, the current densities in H₂/O₂ polymer electrolyte fuel cell at 0.5 V reached ca. 900 mA cm⁻², compared to only ca. 450 mA cm⁻² with our previous approach. This templating process opens the path to a morphological control of Fe–N–C catalysts derived from metal-organic frameworks which, when combined with the versatility of the coordination chemistry of such materials, offers a platform for the rational design of optimized Metal–N–C catalysts.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.