Abstract
We have prepared an yttrium modified Pt(111) single crystal under ultra-high vacuum conditions, simulating a bulk alloy. A Pt overlayer is formed upon annealing the crystal above 800 K. The annealed structure binds CO weaker than Pt(111), with a pronounced peak at 295 K in the temperature programmed desorption of CO. When depositing a large amount of yttrium at 1173 K, a (1.88 × 1.88)R30° structure relative to Pt(111) was observed by low energy electron diffraction. Such an electron diffraction pattern could correspond to a (2 × 2)R30° structure under 6% compressive strain. This structure is in agreement with the structure of the vacancies in a Pt Kagomé layer in Pt5Y rotated 30° with respect to the bulk of the Pt(111). The Pt overlayer is relatively stable in air; however, after performing oxygen reduction activity measurements in an electrochemical cell, a thick Pt overlayer was measured by the angle resolved X-ray photoelectron spectroscopy depth profile. The activity of the annealed Y/Pt(111) for the oxygen reduction reaction was similar to that of polycrystalline Pt3Y.
Highlights
Global energy demand is continuously increasing.[1]
The Pt overlayer is relatively stable in air; after performing oxygen reduction activity measurements in an electrochemical cell, a thick Pt overlayer was measured by the angle resolved X-ray photoelectron spectroscopy depth profile
3 Å of yttrium is deposited on the Pt(111) crystal and the surface segregation is studied as a function of temperature
Summary
Global energy demand is continuously increasing.[1] With limited oil and gas supplies it is desirable to establish an energy economy based on renewable energy.[2] For energy storage much focus has lately been on storing energy in the form of fuels This could e.g. be in the form of alcohols produced from reduction of CO2,3,4 ammonia from the reduction of nitrogen[5] or hydrogen from the electrolysis of water.[6] Much attention has recently been put on hydrogen.[7] One of the most promising technologies for utilising the energy stored in hydrogen is the low temperature polymer electrolyte membrane fuel cell (PEMFC). In order for PEMFCs to become viable, improvements in the catalytic activity of the ORR catalyst are still needed.[9,10,11,12,13,14,15,16,17]
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