Power of broad band sum frequency generation

Due to sensitivity and selectivity of sum frequency generation (SFG), SFG experiments are especially well suited to study electrochemical interfaces and explore adsorbate chemistry in the infrared range. With the use of a broad-band femtosecond laser (BB-SFG), we study platinum electrode surfaces to observe behaviors of electrochemical adsorbates as would be found in fuel cells. BB-SFG is the only existing technique that can observe the vibrational spectra of sub-monolayer coverage with high time resolution. With a 25 micrometer electrolyte gap between the bulk solution and the electrode, no delay between the electrochemical and spectroscopic scans is observed. This has allowed us to observe oxidation reaction intermediates on single crystal and polycrystalline platinum electrodes to study molecular reaction and decomposition pathways. Intermediates, such as bridge, atop, and multifold-bound CO and acetate among others, will be discussed along with description of our future work concerning alternative electrolytes and electrode surfaces.