Broad-band sum frequency generation spectroscopy (BB SFG) was used to obtain vibrational spectra of CO adsorbates produced from formic acid oxidation on a Pt (1 0 0) electrode in sulfuric acid media The BB SFG simultaneously monitored all forms of the CO intermediates including steady state as the potential was scanned at 5 mV/s Spectra were compared to those obtained from CO adsorbed from a CO saturated electrolyte While adsorbed from HCOOH the CO had a sharp atop transition near 2050 cm(-1) and a broader multiply bonded transitions in the 1700-1900 cm(-1) range which appear to result from bridge-like and higher coordinated (possibly fourfold) CO As the potential scanned from -02 to 03 V (vs Ag/AgCl) the bridge-like CO disappeared and the amount of atop CO increased At potentials above 0 5 V the CO was in steady state being oxidized on the surface to CO(2) and replenished by CO from HCOOH These measurements show that BB SFG can observe potential-dependent interconversion of different CO forms on the electrode surface and can measure steady-state reaction intermediates on a surface in real time (C) 2010 Elsevier B V All rights reserved