CO2 electroreduction to multicarbon products in strongly acidic electrolyte via synergistically modulating the local microenvironment

Abstract

Electrochemical CO2 reduction to multicarbon products faces challenges of unsatisfactory selectivity, productivity, and long-term stability. Herein, we demonstrate CO2 electroreduction in strongly acidic electrolyte (pH ≤ 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment. A Faradaic efficiency of 83.7 ± 1.4% and partial current density of 0.56 ± 0.02 A cm−2, single-pass carbon efficiency of 54.4%, and stable electrolysis of 30 h in a flow cell are demonstrated for multicarbon products in a strongly acidic aqueous electrolyte consisting of sulfuric acid and KCl with pH ≤ 1. Mechanistically, the accumulated species (e.g., K+ and OH−) on the Helmholtz plane account for the selectivity and activity toward multicarbon products by kinetically reducing the proton coverage and thermodynamically favoring the CO2 conversion. We find that the K+ cations facilitate C-C coupling through local interaction between K+ and the key intermediate *OCCO.

Localized Alkaline Environment via In Situ Electrostatic Confinement for Enhanced CO2-to-Ethylene Conversion in Neutral Medium

“…14,15,42,46−51 Furthermore, our electrostatic confinement strategy has a universal effect beyond neutral pH conditions. Under acidic electrolytes (pH = 2), where ethylene generation is typically difficult, we can achieve an exceptional FE of 64.5% for ethylene production at a current density of 300 mA cm −2 , which is the highest ethylene FE under acidic conditions reported so far 52 (Figure 2e and Table S4). Meanwhile, the role of the reported carbon-based surface bilayers was attributed to improving the uniformity of current distribution or stabilizing the catalyst surface in the highly alkaline bulk electrolyte, while their effect on modulating the microscopic reaction environment was omitted (our detailed mechanistic studies in the following sessions).…”

Modulating the Cu2O Photoelectrode/Electrolyte Interface with Bilayer Surfactant Simulating Cell Membranes for Boosting Photoelectrochemical CO2 Reduction

“…9−11 Meanwhile, due to the presence of a large number of water molecules and the low solubility of CO 2 molecules (34.2 mM at 1 atm, 25 °C), the PEC CO 2 RR faces the dilemma of poor selectivity and productivity. 12,13 The CO 2 RR is a typical gas-phase reaction that requires efficient capture and activation of CO 2 molecules to produce valuable chemicals. 14 To achieve this, an effective photoelectrode should possess specific catalytically active sites for CO 2 reduction products and promote the diffusion of CO 2 molecules.…”

“…Photoelectrochemical (PEC) CO 2 reduction technology integrates the merits of photocatalysis and electrocatalysis, which is an efficient way to reduce atmospheric CO 2 concentration while storing intermittent renewable energy in chemicals. − Among multiple photocathode catalysts for PEC CO 2 reduction, cuprous oxide (Cu 2 O) has been favored due to its advantages of suitable bandgap (∼2 eV), low toxicity, low cost, and controllable surface-active sites. − During the PEC CO 2 reduction reaction (CO 2 RR), the reactions involved in the cathode chamber include the CO 2 hydrogenation reaction and the undesired competing hydrogen evolution reaction (HER). , The overpotential of the HER is low, while the realization of the CO 2 hydrogenation reaction often requires multiple proton and electron transfers in aqueous electrolytes. − Meanwhile, due to the presence of a large number of water molecules and the low solubility of CO 2 molecules (34.2 mM at 1 atm, 25 °C), the PEC CO 2 RR faces the dilemma of poor selectivity and productivity. , …”

Organic-moiety-engineering on copper surface for carbon dioxide reduction

“…The tuneable and well-defined chemical structure of molecules and polymers provide more possibilities for tuning and mechanistic studies of catalytic activity. [35][36][37]…”