Abstract
In this work, dual-doped TiO2 was successfully synthesized by using tungsten or niobium as the cation and nitrogen as the anion and, as compared with single-doped TiO2, provided a higher electron conductivity and improved physical properties. Platinum (Pt) nanoparticles loaded on these materials showed better electrochemical performance, and the Pt/Ti0.9Nb0.1NxOy and Pt/Ti0.8W0.2NxOy catalysts were 2.6–3.7 times more active than the Pt/Ti0.9Nb0.1Oy and Pt/Ti0.8W0.2Oy catalysts without nitrogen doping. Additionally, there was an activity loss of 22.9% as compared with 81% in Pt/C after 30 000 cyclic voltammetry cycles, a value exceeding the US Department of Energy (DOE) stability target. Dual doping not only enhances the electron conductivity but also changes the electronic state of Pt on the support materials, thus allowing for more active and stable catalysts. Both X-ray absorption spectroscopy (XAS) and density functional theory (DFT) studies were undertaken to demonstrate how defect formation affects the interactions between Pt and the single- or dual-doped TiO2 supports and manipulates the physical and chemical properties of the resulting catalysts. Thus, these catalytic supports are strong candidates for proton exchange membrane fuel cell applications.
Highlights
Fuel cells hold promise as highly efficient devices that directly convert fuels, such as hydrogen and oxygen, into water to produce electrical energy
Platinum (Pt), as a proton exchange membrane fuel cell catalyst, has the best performance among catalytic metals; the high cost of Pt and the lower reaction rate on the cathode, which is the site of the oxygen reduction reaction (ORR), limit the widespread use of proton exchange membrane fuel cells
One critical factor that underlies the corrosion of carbon supports, which leads to sintering and consequent aggregation/loss of catalytic metal nanoparticles, is the weak interaction between Pt and the carbon support.[2]
Summary
Fuel cells hold promise as highly efficient devices that directly convert fuels, such as hydrogen and oxygen, into water to produce electrical energy. Platinum (Pt), as a proton exchange membrane fuel cell catalyst, has the best performance among catalytic metals; the high cost of Pt and the lower reaction rate on the cathode, which is the site of the oxygen reduction reaction (ORR), limit the widespread use of proton exchange membrane fuel cells. Crucial to long-term fuel cell viability is the nature of the support used in the Pt catalyst. Graphitized-carbon supports can be used to replace carbon black, in forms such as nanotubes, nanofibers and graphene nanosheets, to improve chemical and electrochemical stability under the conditions within the fuel cell during the ORR. One critical factor that underlies the corrosion of carbon supports, which leads to sintering and consequent aggregation/loss of catalytic metal nanoparticles, is the weak interaction between Pt and the carbon support.[2]
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