Transition metal
carbides, especially Mo2C, are praised
to be efficient electrocatalysts to reduce CO2to valuable
hydrocarbons. However, on Mo2C in an aqueous electrolyte,
exclusively the competing hydrogen evolution reaction takes place,
and this discrepancy to theory was traced back to the formation of
a thin oxide layer at the electrode surface. Here, we study the CO2reduction activity at Mo2C in a non-aqueous electrolyte
to avoid such passivation and to determine products and the CO2reduction reaction pathway. We find a tendency of CO2to reduce to carbon monoxide. This process is inevitably
coupled with the decomposition of acetonitrile to a 3-aminocrotonitrile
anion. Furthermore, a unique behavior of the non-aqueous acetonitrile
electrolyte is found, where the electrolyte, instead of the electrocatalyst,
governs the catalytic selectivity of the CO2reduction.
This is evidenced by in situ electrochemical infrared spectroscopy
on different electrocatalysts as well as by density functional theory
calculations.