Determination of O[H] and CO Coverage and Adsorption Sites on PtRu Electrodes in an Operating PEM Fuel Cell

Abstract

Abstract:A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the NPt-Ru coordination number increases much slower than the NPt-Pt with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the ∆µ technique and reveal a drop in CO and an increase in OH coverage in the range of 65-90 mA/cm 2 . With increasing OH coverage, the Pt-O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell.

Application of AXAFS Spectroscopy to Transition‐Metal Oxides: Influence of the Nearest and Next Nearest Neighbour Shells in Vanadium Oxides

“…For supported metal particles, the effect of the support on the catalytic properties has been determined by several techniques, for example, XPS, FT-IR analysis of adsorbed CO, and newly developed delta XANES and atomic XAFS (AXAFS) techniques. [8][9][10][11][12][13][14][15] In particular, the application of AXAFS has, in our opinion, led to a better understanding of metal-support interaction effects. [8,[15][16][17] AXAFS is sensitive to changes in the potential around the X-ray absorbing atom.…”

Monte Carlo Simulation of the Solvent Contribution to the Potential of Mean Force for the Phenol Adsorption on Au(210) Electrodes

“…For example, adsorption is involved in the mechanism of charge transfer reactions at electrode surfaces [1][2][3], capacitance dispersion in the electrode/solution interface [4][5][6][7][8][9][10] and self-assembly processes [11][12][13][14][15][16]. As such, adsorption is a crucial subject for various technologic research fields, ranging from surface modification [17][18][19] to heterogeneous catalysis applied to fuel cells [20][21][22]. In the last decades, ab initio quantum calculations, especially those using density functional theory (DFT) [23][24][25][26][27][28][29][30][31][32][33][34][35][36], and molecular simulation techniques, namely Monte Carlo (MC) [37][38][39][40][41][42][43][44][45] and molecular dynamics (MD) [46]…”

Kinetics of Lifetime Changes in Bimetallic Nanocatalysts Revealed by Quick X‐ray Absorption Spectroscopy

“…To this aim, techniques which provide high time resolution, but do not require long range order and can be applied in situ, are crucial for interrogating the kinetic behavior of (often disordered) bimetallic nanocatalysts under operating conditions. For example, in  situ, dispersive and quick X‐ray absorption spectroscopy (XAS) have established a role of utmost importance in uncovering the motifs of (bi)metallic nanoparticle restructuring 13, 14, 15, 16, 17, 18…”