Fascinating Oxygen Reduction on ZIF-derived Fe-N co-doped Carbon composite with graphene

Oxygen reduction reaction (ORR) is the key reaction at the cathode of fuel cells for next-generation electrochemical energy conversion. The sluggish kinetics of ORR makes it the rate-determining step of the whole cell in most cases, thus efficient electro-catalysts are required. Taking advantage of these features, MOFs could serve as both metal and carbon source as well as self-sacrificial templates to prepare complex nanostructures such as porous carbon supported metal nanoparticles and porous metal oxides through thermal conversion [1]. In this study a simple Zn/Fe bimetallic zeolitic-imidazolte frameworks (ZIF) composite with graphene oxide (GO), carbonization method is utilized to synthesize a Fe-N-C hybrid with hierarchical nitrogen-doped porous carbons [2]. Combining MOFs with graphene oxide (GO), their derived carbon composites exhibit enhanced electrochemical performance due to the increased electrical conductivity and density of active sites. However, most of the composites show the unsatisfactory structure and property because of the weak interactions between MOFs and GO, as well as the fast growth kinetics of the MOFs caused nanoparticles aggregation[3]. Since high temperature can enhance the degree of graphitization and also increase the conductivity of catalysts to elevate ORR activity, porous carbon catalysts derived from MOFs must undergo a high-temperature pyrolysis [2]. 14th Annual Electrochemistry Seminar of Iran Materials and Energy Research Center (MERC), 12- 13 Dec, 2018 144 Due to the synergetic effect of bimetal doping the ORR activities of bimetallic MOF-derived porous carbon catalysts are often better than that of single Zn (or Co, Fe) containing MOF-derived ones [3]. In order to investigate the electrochemical properties of the synthesized catalyst, cyclic voltammetry, linear sweep voltammetry and chronoamperometry techniques were used. The results reveal that Fe doping during the ZIF-8 synthesis stage was vital to gain the unique morphology and well dispersed active sites. Furthermore, a high ORR activity of the as-prepared material in both acidic and alkaline media was observed that was attributed to the generated mesoporous, nanostructure derived from MOFs, the proper nitrogen source and the high conductivity of the graphene carbon matrix.