A Synthesis of Efficient Composite Catalyst Based on Fe-N-C Catalyst and Platium for Oxygen Reaction Reduction

Abstract

Globally, because of the consumption of fossil fuel, the proton exchange membrane fuel cells (PEMFC) have received great attention. Among them, direct methanol fuel cells(DMFC) have been applied into many fields, such as computers, global positioning systems(GPS) and portable devices. Platinum catalysts are considered as one of the most efficient catalysts for the oxygen reduction reaction(ORR),which is one of the most essential processes for the DMFC. However, the low methanol resistance limits the application of Platinum catalyst in DMFC. Fe-N-C catalyst has an excellent methanol selectivity and showes a good ORR activitity with great potential as a non-precious metal catalyst. However, the performance of Fe-N-C catalysts is impossible to exceed that of Pt-based catalysts, leading to the irreplacebility of Pt catalyst in DMFC.As a result, the composite catalyst made by Fe-N-C catalyst and Platnum catalyst was synthesized and expected to take advantage of the high methanol resistance of Fe-N-C catalyst and brilliant ORR activity of Platinum catalyst. Herein, we reported a synthesis of an efficient composite catalyst based on Fe-N-C catalyst and Pt catalyst. The Fe-N-C catalyst was gained as described by Piotr Zelenay. Furthermore, 50mg Fe-N-C catalyst dissolved into 12ml isopropanol and 48ml ethanediol was fixed with 4.42ml H2PtCl2-ethanediol solution with a density of 20mg/ml and stirred for 3h. After making the pH of the solution 12 by 1M NaOH-ethanediol and N2 injection for 10 min, the solution was put into the microwave to heat until 130-150 degrees. After cooling to the room temperature, the pH was set as 3 by 1M HNO3. The FeNC-Pt catalyst was obtained after filtration and freeze drying. For RDE tests on the FeNC-Pt catalyst, the ink was prepared by mixing 3mg catalyst dissolved into 2.1ml isopropanol and 29µl Nafion, which was stirred for 40min to achieve a good dispersion. 7µl ink was coated on the surface of RDE, making the loading of Pt 20µg cm-2. The linear sweep voltammetry(LSV) tests were conducted at the speed of 1600rpm in O2 and N2 saturated 0.1M HClO4 solution respectively. The half-wave potential of FeNC-Pt catalysts was about 20mV higher than Pt-C catalyst(0.86V vs 0.84V), which proved a more efficient performance of FeNC-Pt catalyst. The electrochemical areas(ECA) of the catalysts were gained by cyclic voltammetry(CV) tests, and the FeNC-Pt catalyst showed a larger ECA than the Pt-C catalyst. The methanol resistance test was conducted in N2-saturated 0.5M H2SO4-0.5M CH3OH solution, and the FeNC-Pt catalyst showed a better performance. Figure 1