Synthesize ZnFe۲O۴-ZrO۲ as substrate for Pt in Direct methanol fuel cells

In this study, homogeneous and compact ZnFe۲O۴ nanoparticles on the surface of ZrO۲ wassynthesizedas the platinum support for methanol oxidation reaction. Platinum was electrochemicallydeposited on the ZnFe۲O۴-ZrO۲ nanocomposite. The superb electrochemical behavior of the ZnFe۲O۴-ZrO۲ electrode could be ascribed to the nanostructure of ZnFe۲O۴-ZrO۲With the increase of fossil fuel consumption and environment issues, the development of novel energystorage and conversion devices is urgently required. Direct methanol fuel cells (DMFCs) as energyconversion devices possess advantages of low temperature, non-pollution, and high efficient, which havebeen extensively studied [۱]. The performance of DMFCs and SCs always depend on the electrodematerials. Pt-based alloys, Pd-based alloys, and nonprecious metal electrocatalysts have attractedsignificant attention in the field of DMFCs. Precious metal electrocatalysts always possess prefect catalytic ability, while non-precious metals possess inferior catalytic ability. However, precious metalcatalysts suffer disadvantages of high price, low content, and poisoning effect. Therefore, more and moreresearchers focus on the exploitation of novel non-precious metal electrocatalysts with good catalyticability. Meanwhile, conductive polymers, carbon materials, and transition metal compounds are thecommon active materials for DMFCs. Among various materials, transition metal compounds can be usedas the electrode materials both for DMFCs [۲]. Therefore, it is meaningful to design a transition metalcompound, which can be used as substrate catalytic activity for methanol oxidation, simultaneously.Mixed transition metal sulfides have attracted much attention because of their superior conductivity, highelectrochemical activity, and stability. Ternary zinc ferrite zirconium as one of the most promising candidates possess abundant redox reactions and rich electroactive sites, which can be investigated aselectrode materials for electrocatalysts for DMFCs. Herein, we propose a facile method for preparingZnFe۲O۴-ZrO۲/Pt electrodes, and investigate their electrochemical performance in methanolelectrooxidation. As a novel catalyst support, we synthesized ZnFe۲O۴-ZrO۲ for the first time in this study. Using ZnFe۲O۴-ZrO۲/Pt electrocatalyst alloy on modified carbon paste electrodes, Ptelectrocatalyst alloy was electrochemically deposited on the surface of ZnFe۲O۴-ZrO۲. This was used asthe anode catalyst for MOR [۳].Fig. ۱ illustrates the electrochemical activity of ZnFe۲O۴-ZrO۲/Pt compared with Pt commercial in MOR These CV traces in Fig. ۱ were recorded in a solution of۱.۰ M CH۳OH+ ۰.۵ M KOH at a rate of ۵۰ mV s-Referring to Fig. ۱, the CVs of the two electrocatalysts have two methanol oxidation peaks approximately located at ۰.۴ and -۰.۲۹ V in the forward and reverse scans, respectively. The peakobserved in in the positive-going scan originates from the oxidation of methanol molecules adsorbed onthe surface of the catalyst leading to the formation of carbonaceous intermediates on the surface of theelectrode. In the negative-going potential scan, the peak centered around -۰.۲۹ V may be due the residual methanol molecules oxidation adsorbed on the catalyst active sites, and also the oxidation of theremaining carbon-based materials (such as CO) which were not been removed from the catalyst surface inthe preceding anodic scan. As shown in Fig. ۱, the maximum anodic current density generated byZnFe۲O۴-ZrO۲/Ptsample reaches ۱۱۰ mA cm-۲ that is almost ۴۲ % higher than that of Pt commercialelectrocatalyst (۶۰.۲۷ mA cm-۲). The onset of methanol oxidation can be considered as an importantparameter to probe the electrochemical performance of the prepared electrocatalysts in MOR at lowpotential regions. It is seen in Fig. ۱ that the onset potential of ZnFe۲O۴-ZrO۲/Ptsample is more negativethan that of Pt electrocatalysts (-۰.۵۴ V vs. -۰.۴۸ V). This observation indicates that the ZnFe۲O۴-ZrO۲/Ptelectrocatalyst is capable of promoting MOR when compatred with pure Pt electrocatalysts [۴].Figure Figure ۱. CVs of ۱.۰ M CH۳OH in ۰.۵ M KOH on ZnFe۲O۴-ZrO۲/Pt and Pt samples recorded at a sweeprate of ۵۰ mV s-۱.Using a simple hydrothermal technique, nanospherical ZnFe۲O۴-ZrO۲ mixed metal oxide nanocompositeswith varying ratios were effectively manufactured.Following that, Pt nano-electrocatalyst waselectrochemically deposited on the surface of the ZnFe۲O۴-ZrO۲ nanocomposite. To our knowledge, this isthe first report on the demonstration of a ZnFe۲O۴-ZrO۲ nanocomposite in a supercapacitorapplication.The ZnFe۲O۴-ZrO۲/Pt particles displayed a high current density of ۱۱۰ mA/cm۲ with an onsetpotential of -۰.۴ V when used as a catalyst for MOR

کلیدواژه ها:

ZnFe۲O۴-ZrO۲ ، Nanocomposite ، Methanol oxidation reaction ، Platinum