We have recently developed a unique vacuum inlet system, which couples a mass spectrometer to an electrochemical experiment like a conventional DEMS/OLEMS system – but with an unprecedented combination of quantitative and ultrasensitive product detection with sub-second time resolution. [1]

Using this one-of-a-kind tool, we experimentally map out the behavior of Cu-based CO reduction. In particular, we study transient overproduction of methane. We find that a very pronounced, overproduction of methane (compared to ethylene) is the result of an electrochemical pre-treatment of the catalyst with molecular oxygen dissolved in the electrolyte. Mechanistic implications are discussed.

[1] D. B. Trimarco et al., Rev. Sci. Instrum. 86, 075006 (2015)