Controlling the selectivity of CO2 electroreduction on copper: The effect of the electrolyte concentration and the importance of the local pH

Reactivity of Copper Electrodes towards Functional Groups and Small Molecules in the Context of CO2 Electro-Reductions

“…Bertheussen et al [52] recently reported the observation of considerable quantities of acetaldehyde (16) in an authentic electrolysis experiment and demonstrated the authentic bulk electro-hydrogenation of acetaldehyde (16). We attempted to reproduce these results and also intended to demonstrate the ethene (12) from acetaldehyde (16).…”

“…In this mechanism, ethene (12) is produced by dimerisation of two methylene (10) units. Ethanol (17) is formed by carbonylation of one methylene (10) to ketene (13) and two subsequent reduction steps to acetaldehyde (16) and ethanol (17). Both these mechanisms feature acetalydehyde (16) as an intermediate.…”

“…Ethanol (17) is formed by carbonylation of one methylene (10) to ketene (13) and two subsequent reduction steps to acetaldehyde (16) and ethanol (17). Both these mechanisms feature acetalydehyde (16) as an intermediate. In the first mechanism, it is the "Selectivity Determining Intermediate" (SDI) and precursor to ethene (12) and ethanol (17) [44][45][46].…”

“…Copper-catalyzed CO 2 reduction to hydrocarbons was first reported by Hori in 1985 [10]. In the following decades, publications using copper electrodes [11][12][13][14][15][16][17], copper oxide electrodes [18][19][20][21], copper-containing perovskites [22], oxide-supported copper catalysts [23], halide-derived copper catalysts [24][25][26][27], copper-based alloys [28], copper-based metal-organic frameworks [29], molecular copper complexes [30], as well as alternative systems [5,[31][32][33][34][35][36] vastly increased. Also pyridine-based co-catalysis known from Pd electrodes [37] could recently be transferred to copper-based systems [38].…”

Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction

“…6,7 However, the explanation becomes more complicated when dealing with nanostructured copper materials derived from oxidized precursors, which show both higher activity and greatly enhanced selectivity towards multicarbon products. [8][9][10][11][12][13][14][15][16] It has been hypothesized that this could be related for instance to an increase of local pH, [17][18][19] grain boundaries, 20 undercoordinated sites, 21 or residual oxides. [22][23][24] Several groups have shown the existence of sites with higher CO binding energy in oxidederived copper.…”