MIL-101(fe) derived cofe nanomaterials for electrocatalytic oxygen reduction reaction
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Date
2023
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UMT, Lhr
Abstract
The combustion of fossil fuels has long been recognized as a major contributor to the increase in greenhouse gas emissions, particularly carbon dioxide (CO2), leading to the capture of heat returning from the Earth's surface and subsequent global warming. As a response to the urgent need for clean and sustainable energy, fuel cells and metal-air batteries have emerged as proven technologies. These systems rely on electrochemical reactions, with the oxygen reduction reaction (ORR) playing a pivotal role in their overall performance. Understanding the factors influencing the activity and selectivity of ORR catalysts is crucial for the development of efficient and selective catalysts, contributing to the advancement of clean energy applications. In this context, the exploration of various carbon supports, Fe precursors, and the role of nitrogen content has become an integral aspect of catalyst design. The ongoing quest for enhanced catalyst performance has led to innovative approaches, and one such approach involves the synthesis and modification of metal-organic frameworks (MOFs). In this particular study, the MOF MIL-101 (Fe) serves as the precursor for the synthesis of an efficient ORR catalyst. The MOF is subjected to a controlled sonication process with melamine, cobalt nitrate hexahydrate (Co(NO3)2.6H2O), and iron nitrate nonahydrate (Fe(NO3)3.9H2O). The resulting composite undergoes calcination under an argon atmosphere, leading to the creation of a highly effective catalyst for ORR. By adjusting the concentration of Fe(NO3)3.9H2O while keeping the concentrations of MIL-101, Co(NO3)2.6H2O, and melamine constant, various materials with distinct ratios are synthesized. Characterization of the resulting materials conducted through powder X-ray diffraction studies, providing insights into their structural composition and crystallographic features. The catalytic activity of these materials further assessed using a three-electrode system with a rotating disc electrode (RDE) serving as the working electrode. Among the synthesized materials, denoted as Co/Fe@1, Co/Fe@2, Co/Fe@3, and Co/Fe@4, Co/Fe@3 stands out as a particularly effective catalyst for selective O2 reduction. Co/Fe@3 exhibits superior ORR activity when tested in a 0.1 M KOH solution, showcasing comparable performance to the benchmark catalyst (20 wt% Pt/C). Key electrochemical parameters, such as onset potential of 0.99 V, a Tafel slope of 57 mV dec-1, current density of 5.22 mAcm-2, and a half-wave potential of 0.87 V, highlight the efficacy of the synthesized material. Notably, this material opens a pathway for the fabrication of effective ORR catalysts based on iron, a metal traditionally deemed less active in ORR processes. In summary, the synthesis and modification of MOFs for the development of efficient ORR catalysts represent a promising avenue in the pursuit of sustainable energy solutions. The meticulous exploration of various parameters in the synthesis process, coupled with comprehensive characterization and electrochemical assessments, contribute to the ongoing advancements in the field of catalyst design for clean energy applications.