Porous carbon nanosheets derived from ZIF-۸ with transitional metal ascathode proton exchange membrane fuel cell

Currently, an increasing world appeal for energy, and the environmental pollution challenges of fossilfuel such as greenhouse gases, global warming and climate change have enforce world scientistcommunity to explore an alternative environmentally friendly renewable energy sources [۱]. In recentyears, fuel cell which is an energy conversion tool has attracted a considerable attention [۲]. Amongdifferent types of energy conversion device, hydrogen fueled proton exchange membrane fuel cell(PEMFC), have shown an exceptional characteristics, including low operating temperature (<۹۰ °C),easy-to-handle, environmental sustainability and higher efficiency [۳]. However, PEMFC hasexperienced low performance caused by the slow oxygen reduction reaction (ORR) at the cathode,therefore catalyst is needed to improve the sluggish kinetics of ORR process. For many years, acommercial platinum metal catalyst supported by carbon black (Pt/C) has being traditionally used toimprove ORR cathode reaction kinetics. Although Pt/C catalyst promoted ORR reaction, higher priceand low availability prevented to be use in the large scale PEMFC operation. In the past decade, greatefforts have been made in the development of cheaper and abundant non noble catalysts basednanoporous carbon for ORR enhancement in PEMFC cathode. ORR is a complex reaction with eithertwo or four reaction pathway that involve different mechanisms associated with multiple adsorptions,desorption, dissociation of oxygen. It is widely considered that zeolitic imidazolate frameworks (ZIFs)derived porous nitrogen doped carbon (NC) possess an effective electrocatalytic acitiviy towards thefacilitation of oxygen reduction and charge transfer, promoting ORR performance [۴]. ZIFs are subgroup of metal organic frameworks (MOFs), which are mainly prepared from the mixing of organicimidazolate ligand and inorganic metal salt (Zn or Co) in a solvothermal method [۵].In this study, different catalyst support materials pyrolysis temperatures of ۸۰۰ °C) were successfullyderived from the pyrolysis of pristine ZIF-۸, single and double metal doped.The catalyst supports were physically characterized by XRD, SEM/ED-S, elemental analysis, andRaman spectra. The prepared catalyst support materials were loaded and their ORR electrocatalystproperties were studied in with polarization curves. The high specific area, porous structure, andabundant catalytic Co, Mn, and N species gave rise to the ORR performance of the catalyst. As aresult, the as-prepared CoNC, Mn-NC, and Co-MnNC catalysts showed an onset potential of ۰.۷۲,۰.۷۹, and ۰.۸۹ V in ۰.۱ M HClO۴ with ۱۶۰۰ rpm, respectively (see table ۱). This work is conductive tothe rational design and synthesis of ZIF-based hybrid materials and ZIF-derived carbon materials.

Keywords:

Oxygen reduction reaction , Precious-metal-free catalyst , PEMFCs