Vibrational sum-frequency generation study of the CO2 electrochemical reduction at Pt/EMIM-BF4 solid/liquid interfaces

Björn Braunschweig, Prabuddha Mukherjee, John L. Haan, Dana D. Dlott

Research output: Contribution to journalArticlepeer-review

Abstract

Electrochemical reduction of CO2 on polycrystalline Pt catalysts in a 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]BF4 room-temperature ionic liquid (RTIL) is not impaired by well-known effects such as high ohmic losses or vigorous hydrogen evolution reactions. Vibrational broadband sum-frequency generation (SFG) combined with cyclic voltammetry has been applied to identify the formation of a [CO2-EMIM] complex at the interface which gives rise to a SFG active vibrational mode at 2355 cm− 1. The [CO2-EMIM] complex serves as a stable precursor to CO2 reduction and is linked to a remarkable small potential barrier for CO2 reduction and subsequent CO production. Vibrational SFG spectra reveal CO linearly bonded to Pt atop sites as the predominant surface-adsorbed reduction product. Extended electrochemical reduction of CO2 results in an intense CO band and an electrochemical Stark tuning rate of 33 cm− 1/V at potentials >− 0.2 V vs. SHE which is indicative of a close-packed CO adlayer. Anomalous Stark tuning for potentials <− 0.2 V is observed and attributed to hydrogen co-adsorption from residual H2O into the CO adlayer. CO modification of Pt leads to considerable reduction of the observed reduction current density that is caused by a poisoning effect of the CO adlayer that persists at the interface for + 0.5 to − 0.8 V.

Original languageEnglish (US)
Pages (from-to)144-150
Number of pages7
JournalJournal of Electroanalytical Chemistry
Volume800
DOIs
StatePublished - Sep 1 2017

Keywords

  • CO electroreduction
  • Catalysis
  • Platinum
  • Spectro-electrochemistry

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemical Engineering(all)
  • Electrochemistry

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