Probing the Dynamics of CO2 Electroreduction with Time-Resolved SERS
Jim de Ruiter a, Ward van der Stam a
a Debye Institute for Nanomaterials Science, Utrecht University, Heidelberglaan, 8, Utrecht, Netherlands
Proceedings of International Conference on Frontiers in Electrocatalytic Transformations (INTERECT)
València, Spain, 2021 November 22nd - 23rd
Organizers: Elena Mas Marzá and Ward van der Stam
Poster, Jim de Ruiter, 013
Publication date: 10th November 2021

The electroreduction reaction of CO2 (eCO2RR) into hydrocarbons over copper electrodes has been studied extensively for the past few decades.[1] However, the eCO2RR mechanism, the activation of CO2 and the exact surface structure of the copper electrode are still heavily debated.[2] Raman spectroscopy is suitable for in situ characterization of CO2RR mechanisms, but the low signal intensity and resulting poor time resolution (often up to minutes) hampers the application of conventional Raman spectroscopy for the study of the reaction dynamics, which requires sub-second time resolution. In this presentation, I will discuss the development of time-resolved Raman spectroscopy (TR-Raman) with (sub) second time resolution, which allows us to investigate the electrocatalytic activation of CO2 and the dynamic chemical structure of the electrode surface.[3] By subsequently measuring different Raman regions during a cyclic voltammetry scan, we are able to collect a broad range of vibrational modes related to adsorbed species (i.e. carbonate & CO) or the active surface (i.e. copper oxide and hydroxide) with sub-second time resolution. Our TR-Raman measurements reveal that the electrode surface is dynamic in the first seven seconds of cathodic bias onset due to stripping of surface Cu oxide species, after which the surface stabilizes as copper hydroxide due to local alkaline conditions.[3] After that, dynamic coupling of surface-bound carbon monoxide (CO) intermediates into ethylene is observed at an applied potential of -0.9 V vs. RHE, whereas lower cathodic bias (−0.7 V vs. RHE) results in gaseous CO production from isolated and static CO surface species. Furthermore, we observe the potential- and time-dependent adsorption of carbonate and bicarbonate electrolyte ions, which is a measure for variations in local alkaline conditions. Our combined electrochemical and TR-Raman measurements provide detailed information about the chemical structure of and the chemical landscape at the copper surface under reaction conditions.

 

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