Towards the elucidation of the high oxygen electroreduction activity of Pt_xY: surface science and electrochemical studies of Y/Pt(111)

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.

Atomic-scale restructuring of hollow PtNi/C electrocatalysts during accelerated stress tests

“…Recently, using a "hard templating" method based on galvanic replacement and the nanoscale Kirkendall effect, we and other groups synthesized hollow PtCo/C or PtNi/C nanoparticles to electrocatalyze the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs) [3,4,[7][8][9]11]. Alloying Pt with a 3d transition metal such as Co, [12][13][14][15][16][17][18] Ni, [14,15,[19][20][21] Y, [22,23] Sc, [24] or Gd, [25] is a common way to tailor the chemisorption energies of oxygen-containing ORR intermediates via strain [26][27][28][29][30] and ligand [31][32][33] effects. This in turn affects the preexponential term of the Arrhenius equation and thus enhances the ORR rate.…”

Exploring the phase space of time of flight mass selected PtxY nanoparticles

“…[39][40][41] In our laboratory we have taken a different approach, namely to study alloys of Pt and rare earths such as Y, Gd, Ce and La. 33,[42][43][44][45][46][47][48] These alloys have a particularly negative heat of formation, which should provide them with long term-kinetic stability against dealloying at the cathode of a fuel cell. Extended surfaces of Pt 3 Y and Pt 5 Gd show particularly high activity for oxygen reduction.…”

“…Extended surfaces of Pt 3 Y and Pt 5 Gd show particularly high activity for oxygen reduction. 42,43,47 On the other hand, upon exposure to reaction conditions, alloys such as Pt 2 Y or PtY corroded extensively, due to Y dissolution; this suggests that an excessive amount of Y is detrimental to catalyst stability. 44 Most recently, we demonstrated that Pt x Y is also highly active for the oxygen reduction reaction in nanoparticulate form.…”

Electrochemical Kinetics: a Surface Science-Supported Picture of Hydrogen Electrochemistry on Ru(0001) and Pt/Ru(0001)

“…Technically, those rely on particles of electrocatalysts, but research makes frequent use of planar single crystalline systems as model surfaces. Among other advantages, those allow more specific insights on the role of adsorbed species for key reactions such as hydrogen evolution/oxidation (HER/HOR) [33][34][35], CO oxidation [21,22,36,37], and oxygen reduction (ORR) [3,27,38,39]. From a fundamental research point of view, planar model surfaces come with the advantage that they closely resemble the slabs that are used in density functional theory (DFT) calculations [40][41][42].…”

“…The synergy between vacuum-based analysis and electrochemistry has a long history [1][2][3][4][5][6][7]. However, particularly for low mass and highly mobile species such as hydrogen, the direct quantification of coverages by in situ electrochemical techniques, which by now are highly developed [8][9][10][11][12][13], has still proven elusive.…”