Modulating the Product Distribution of the Electrochemical Reduction of CO2 on Copper at Relevant Current Densities

Abstract

The electrochemical reduction of CO2 (CO2RR) has the potential to be an economically-viable method to produce platform chemicals synergistically with renewable energy sources. Copper is one of the most used electro-catalysts for this purpose, as it allows carbon-carbon bond formation, crucial for broader product distribution. Despite great achievements, controlling selectivity is yet a stepping stone between R&D and an actual industrial application. Among others, a kinetic resolution could be applied to enhance the selectivity toward targeted products, for which exploiting available and inexpensive additives or co-electrolytes such as ionic liquids is a promising direction. Herein, we present an initial systematic analysis of the effect of various tetra alkyl ammonium salts on the CO2RR products distribution with the aim on ethylene, important industrial feedstock or building block. A selected ammonium salts of different alkyl chain length and number of charges provided very concise but sufficient chemical space to overview a structure-activity relationships, including changes in the reactions’ onset potentials and limiting currents. The overall experimentation progress was intensified by the employing a developed in our lab a gas diffusion electrode (GDE) cell, coupled to a mass spectrometer. This enabled to scan the selected library of salts during CO2RR under dynamic operations with detection of transients in real-time at relatively high current densities, between 10 to 400 mA/cm2, within further quantitative validation over standard long-term steady-state experiments. These results have broad implications for effectively stirring the CO2RR selectivity towards products containing either one or two carbon atoms.Key words: CO2, Electroreduction, Copper, Electrocatalysis, Modifiers, Real-time, GDE