Abstract
Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO2) according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO2 is synthesized and deposited over a commercial grade of carbon (Vulcan XC72) by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation), followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn2O3 and Mn3O4) with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H2SO4), evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-MnxO1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst.
Highlights
IntroductionFuel cells are electrochemical devices that produce electricity from the energy of a fuel through a highly efficient conversion process, resulting in low emissions and low environmental impact [1]
Fuel cells are electrochemical devices that produce electricity from the energy of a fuel through a highly efficient conversion process, resulting in low emissions and low environmental impact [1].Between the different types of fuel cell, Direct Alcohol Fuel Cells (DAFC) and Direct Methanol Fuel Cells (DMFC), represent a valid alternative for small portable electronic devices and auxiliary power units, due to the high energy density of alcohols, their lightweight and compact nature and their ability for fast recharging [2,3].Platinum is the most widely used catalyst for both the anodic methanol oxidation reaction (MOR)and the cathodic oxygen reduction reaction (ORR) [4,5]
The results show that Pt/C-MnxO1+x is more stable compared to Pt/C, showing an increase of electrochemical active surface area (ECSA) (+29% after 5000 cycles, Figure 8A)
Summary
Fuel cells are electrochemical devices that produce electricity from the energy of a fuel through a highly efficient conversion process, resulting in low emissions and low environmental impact [1]. This would lead to a reduction of the total Pt loading on the electrode For this purpose, reaction rates need to be enhanced (i.e., the overvoltage needs to be decreased) by modifying the catalyst composition or structure, to produce a more active electro-catalytic material [7]. Non-noble metal oxides (M-Ox) such as WO3, CeO2, V2O5, Nb2O5, MoOx, ZrO2, TiO2, MgO and MnO2, exhibit suitable surface properties which can efficiently promote the methanol and ethanol electro-oxidation reactions combined with Pt/C [10]. A good strategy to improve the catalytic activity of Pt-based catalysts for MOR is to use metal oxides in the catalyst supports, as a hybrid structure (C + M-Ox) [11]. MnO2 with smaller and uniform crystalline orientation as well as suitable surface morphology should offer apposite active sites for facile interaction with Pt crystallites, which can provide optimized synergistic effect for alcohol electro-oxidation [14]. The synthesized catalyst was compared with two commercial Pt-based catalysts characterized and tested for MOR in acidic medium
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