In our group, we focus on employing the 2nd order nonlinear optical spectroscopy, mostly vibraitonal sum frequency generation (SFG) to study various fundamental processes at the electrochemical interfaces. These include the adsorption of solvent and ions on the single crystal electrodes, the reaction intermediates for important electrochemical catalytic reactions (i.e. ORR, HER, electrochemical oxidation of small organic molecules), and also the structure of the charge carrier during the heterogeneous charge transfer processes (i.e. solvated electron, hydronium and anions). As a compensation of the optical probing method, we also detect the nonlinear electrical signal, i.e. photo current/voltage, that induced by two sequential ultra-shot laser pulses with desired frequencies for ultra-fast electrochemical processes.

Tong, Y.; Campen, R. K. In Situ Probing of Adsorbates at Electrochemical Interfaces with Vibrational Sum Frequency Spectroscopy. in: Klaus Wandelt (ed.) Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Volume 1.1: Experimental Methods, pp 280-286. Elsevier Inc. (2018), Zwaschka, G.; Wolf, M.; Campen, R.K.; Tong, Y. Microscopic Model of the Electrochemical Vibrational Stark Effect: Understanding VSF Spectroscopy of (bi)Sulfate on Pt(111) Tong, Y.; Zhang I.Y.; Campen, R. K. Experimentally Quantifying Anion Polarizability at the Air/Water Interface. Nature Communications 9, 1313 (2018). Tong, Y.; Lapointe, F.; Thämer, T.; Wolf, M.; Campen, R. K. Hydrophobic Water Probed Experimentally at the Gold Electrode/Aqueous Interface. Angewandte Chemie. 129, 4275 (2017) / Angew. Chem. Int. Ed. 56, 4211 (2017). Garling, T.; Tong, Y.; Darwish, T. A.; Wolf, M.; Campen R. K. The Influence of Surface Potential on the Optical Switching of Spiropyran Self Assembled Monolayers. Journal of Physics: Condensed Matter. 29, 414002 (2017). Tong, Y., Kampfrath, T.; Campen, R.K. Experimentally probing the libration of interfacial water: the rotational potential of water is stiffer at the air/water interface than in bulk liquid. Phys. Chem. Chem. Phys. 18, 18424 (2016). Tong, Y.; Cai, K.; Wolf, M.; Campen, R. K. Probing the electrooxidation of weakly adsorbed formic acid on Pt(1 0 0). Catalysis Today, 260, 66-71 (2016). Kirsch, H.; Tong, Y.; Campen, R. K. Experimental Characterization of CCH(ads) and CCH2(ads) during the Thermal Decomposition of Methane and Ethylene on Ru(0 0 0 1). ChemCatChem, 8, 658-658 (2016). Wirth, J. A.; Kirsch, H.; Wlosczyk, S.; Tong, Y.; Saalfrank, P.; Campen, R. K. Experimental Characterization of CCH(ads) and CCH2(ads) during the Thermal Decomposition of Methane and Ethylene on Ru(0 0 0 1). Phys. Chem. Chem. Phys., 18, 14822-14832 (2016). Wu, H.-L.; Tong, Y.; Peng, Q.; Li, N.; Ye, S. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). Phys. Chem. Chem. Phys., 18, 1411-1421 (2016). Tong, Y.; Peng, Q.; Ma, T.; Nishida, T.; Ye, S. Photocatalytic Oxidation of the Organic Monolayers on TiO2 Surface Investigated by in-situ Sum Frequency Generation (SFG) Spectroscopy. APL Materials, 3, 104402 (2015). Tong, Y.; Wirth, J.; Kirsch, H.; Wolf, M,; Saalfrank P.; Campen, R.K. Optically probing Al—O and O—H vibrations to characterize water adsorption and surface reconstruction on α-alumina: An experimental and theoretical study. J. Chem. Phys., 142, 054704 (2015). Ye, S.; Tong, Y.; Ge, A.; Qiao, L.; Davies, P. Interfacial Structure of Soft Matter Probed by SFG Spectroscopy. Chem. Rec., 14, 791-805 (2014). Kirsch, H.; Wirth, J.; Tong, Y.; Wolf, M,; Saalfrank P.; Campen, R.K. Observing the hydration layer of trehalose with a linked molecular terahertz probe. J. Phys. Chem. C,, 118, 13623–13630 (2014).