The influence of pH on the reduction of CO and CO2 to hydrocarbons on copper electrodes

Electroreduction of Carbon Monoxide Over a Copper Nanocube Catalyst: Surface Structure and pH Dependence on Selectivity

“…This has been well documented, particularly by Hori et al,a nd is the reason for the recent interesti n the investigation of local pH effects. [2b, [6][7][8] Schouten et al investigated the reductiono fs everalp otential reactioni ntermediates and concluded that the mechanism for ethylene production proceeded through aC Od imerizationm echanism. [7] Montoya et al expanded on this idea by using DFT studies and they attribute the shift of the ethylene onset on the RHE scale to CO dimerization that is an electron transfer step only (no proton transfer required), and is, therefore, fixed on the standard hydrogen electrode (SHE) scale.…”

Mechanistic Insights into the Unique Role of Copper in CO2 Electroreduction Reactions

“…[4,17] In addition, the presence (absence) of proton transfer before the rate-limiting step for the CH 4 (C 2 H 4 )p athway also explainst he experimentally observed pH independence (pH dependence) of CH 4 (C 2 H 4 )f ormationo nt he RHE scale. [34] Note that on Cu(2 11)t he adsorption free energy of CO* with the subsurface C* is 0.27 eV,s maller than the value of 0.61 eV without the subsurface C*, signifying that some C* monomers stay alone, without forming CCO* during reactions. With increasing overpotential, our model predicts that the C 2 H 4 pathway,a sw ell as the formation of C* monomers, accelerate the consumption of CO*, as the experiments found.…”

“…[23],t he damage of the H-bonding network costs more than 0.80 eV per H 2 O, again suppressingt he formation of the www.chemsuschem.org CO* dimer.T his conclusion also holds true for Cu(111). As the formationo fC O* dimers is argued to largely depend on electric fields, [16,23,34] we also try to constructC O* dimers by tuning the electric field on Cu surfaces:aproton is introduced to OH* on Cu(2 11)a nd H 2 O* on Cu(111)( the later process is energetically favored). Unfortunately,t he formationo ft he CO* dimer still costs more energy (with barriers > 1.50 eV) than the formation of separated CO* monomers ( Table 1).…”

Competition between H and CO for Active Sites Governs Copper‐Mediated Electrosynthesis of Hydrocarbon Fuels

“…[11][12][13][14][15][16] However,t hese studies alone are unable to parse reaction mechanisms.I ndeed, studies of the COdependent kinetics of higher-order product formation are uniquely suited to distinguish different mechanistic possibilities because they directly probe kinetically relevant intermediates and provide reaction orders for each product. [8,17,18] However,w hile excellent studies have investigated the pH, electrolyte cation, and crystal facet dependence of the reaction, [19][20][21][22][23][24][25][26][27][28][29] investigations of the CO-dependent kinetics have thus far been hampered by the low solubility of CO in aqueous electrolytes (1.1 mm), [30] which severely restricts the concentration range over which activation-controlled CO reduction kinetics can be probed. Furthermore,t he mechanistic regimes become distinguishable at near saturation CO coverage,t herefore requiring an experimental approach that fosters strong CO binding to the Cu surface.…”