Shape resonances and EXAFS scattering in the Pt L-2,3 XANES from a Pt electrode

Atomic hydrogen and oxygen adsorption on a platinum electrode in H2SO4 and HClO4 electrolytes were studied by Pt L-23 XANES. The Pt electrode was form ed of highly dispersed 1.5-3.0 nm particles supported on carbon. A differen ce procedure utilizing the L-2 acid L-3 spectra at various applied voltages was used to isolate the electronic and geometric effects in the XANES spec tra. At 0.54 V (relative to RHE) the Pt electrode in HClO4 is assumed to be "clean". By taking the difference between the spectra at 0.0 and 0.54 V, t he Pt-H antibonding state (electronic effect) is isolated and found to have a Fano-resonance line shape. In addition, a significant R-K EXAFS scatteri ng (geometric effect) was found for photon energies 0 to 20 eV above the ed ge. The difference between the spectra at 1.14 and 0.54 V allows isolation of the Pt-O antibonding state and the Pt-O EXAFS scattering.