Vibrational Sum Frequency Spectroscopy study of CO 2

Vibrational Sum Frequency Spectroscopy study of CO 2 electroreduction Click totheedit Master title mediated by ionic liquid-water on Ag style Natalia Garcia Rey and Dana D. Dlott University of Illinois at Urbana-Champaign International Symposium on Molecular Spectroscopy 70 th Meeting, Champaign-Urbana

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CO 2 electroreduction at low-overpotential o Ionic liquid mediated the CO 2 electroreduction into CO at low-overpotential 1, 2. o Water increases Faradaic efficiency. Ionic liquid: EMIM-BF 4 CO 2 H 2 O Ag CO H 2 (1) Rosen, B. A. et al. , Science 2011, 334, 643; (2) Rosen, B. A. et al. , J. Electroch. So. 2013, 160, H 138.

Vibrational sum frequency spectroscopy synchronized with cell potential allowed us to… o CO produced in the cell from the CO 2. CO adsorbs on Ag but not poisons the electrode CO stretching mode at IR 2100 cm-1. o The ionic liquid-water-Ag interface controls the CO 2 electroreduction nonresonant sum frequency at IR 2600 cm-1. o Water concentration shifts the structural orientation to lower potentials nonresonant sum frequency at IR 2600 cm-1.

VSFS-CV setup potentiostat computer CCD computer potentiostat counter electrode reference electrode Ti: sapphire Laser 120 fs 800 nm 1. 8 m. J @ 3 k. Hz Rep. rate optical parametric amplifier (OPA) 2. 5– 16 µm 4µJ @ 5µm trigger CCD lens grating slit Ag/Ag. Cl CO 2 Pt spectrograph short-pass filter (738 nm) Fabry-Perot étalon Ge filter BBIR delay stage NBvis Luggin cappilary 60° VSFS polarization analyzer

CO 2 electroreduction in situ on cathode mediated by room temperature ionic liquid (RTIL) EMIM-BF 4 Ca. F 2 window O OC BF 4 - O H H O OCO O C OCO O C BF 4 - + + O C O O H H OC O O H H O OC O C OCO BF 4 - + C O O H H H OC O OC BF 4 - O H H BF 4 - + BF 4 - O H H OCO + 25 mm electrolyte BF 4 - + BF 4 - O + O C BF 4 - O H H C BF 4 - O HO H OCO EMIM+ BF 4 - Ag working electrode negative potential diffuse region double layer inner region onset of CO 2 reduction +

CO 2 electroreduction in situ on cathode mediated by room temperature ionic liquid (RTIL) EMIM-BF 4 Ca. F 2 window OO H CH O OC BF 4 - O OCO O C OCO O O C O OC + + + O C O O H H O O O C CO C BF 4 - + O OC O O H H C OCO O C - BF 4 + C O +O BF 4 - O O H H O H O H H OC O + O C BF 4 - O H H O - C OCO + O H H BF 4 - O O BF 4 - O C + O + O C O H H C BF 4 - O HO H OCO EMIM+ BF 4 - Ag working electrode negative potential O C 25 mm electrolyte Ar diffuse region double layer inner region CO 2 onset of CO 2 reduction

Resonant VSFS vs Cell Potential CO 2 electroreduction in EMIM-BF 4 / 0. 3% H 20 / Ag CO stretching mode 22 cm-1/V *mol% of water

Nonresonant VSFS vs Cell Potential CO 2 electroreduction EMIM-BF 4 / 0. 3% H 20 / Ag VSFS V VIS Pot ent ial v s Ag /Ag Cl / IR

Nonresonant SF vs cell potential: CO 2 electroreduction in EMIM-BF 4 / 0. 3% H 20 / Ag

Addition of water Neat EMIM-BF 4 adding mol % by mol of water 130 m. V cell potential (V)

Take home message o CO 2 electroreduction into CO was observed. A minimum in the nonresonant SF was found at the same potential, -1. 33 V. Click to edit Master title o style CO was the specie mainly produced, not poisoning the Ag electrode o The structural transition of the water-EMIM-BF 4 on Ag, the double layer, mediated the CO 2 electroreduction. o Increase in water concentration shifts the EMIM-BF 4 on Ag structural transition to a lower cell potentials.

Acknowledgments Prof. Dana D. Dlott’s group Click to edit Master title Thank you all for your style attention! Any questions?