Electrochemical CO₂/CO Reduction and C–C Coupling Path for Mimicking Fischer–Tropsch Synthesis over Cadmium Electrodes

Abstract

Converting CO2 into C n>2 hydrocarbons has been a significant challenge, but recent research has shown that cadmium (Cd) can be used to produce C2–7 hydrocarbons (C n H2n and C n H2n+2) directly through electrochemical CO2 reduction in a K2HPO4/KH2PO4 buffer. The production of hydrocarbons was found to be enhanced by engineering the interface of the Cd surface with other transition metals. This process imitates the Fischer–Tropsch (F–T) synthesis, which involves surface polymerization reactions that couple carbon atoms together, resulting in the formation of long-chain hydrocarbons via the insertion of CO and CH x molecules. While the formate path was almost completely suppressed, the CO path remained. While the current Faradaic efficiency may be low, this study highlights the potential of electrochemical CO reduction for Cd. The study demonstrates that CO and H can directly participate in F–T synthesis through electrochemistry. Furthermore, Cd was observed to recrystallize into stacked wall structures resembling flowers after the electrochemical process. As a result, this research provides crucial insights that can aid in a better understanding of C–C coupling paths via electrochemistry.

Ag–Sb/Cu by Galvanic Replacement: Electrochemical CO2 Reduction and Unveiling C3+ Hydrocarbon Pathways

“…The production of C 3+ hydrocarbons, as well as C 2 hydrocarbons, may involve novel reaction pathways. Considering the linearity observed in the ASF plots, the production mechanism of C 2+ hydrocarbons appears to follow the conventional F–T synthesis mechanism. − ,, In the C–C coupling polymerization F–T synthesis, the CO or CH x insertion reactions contribute to the formation of longer hydrocarbon chains. Example reactions include CH 3 C* + *CO + 4H + + 4e – → CH 3 CH 2 C* + H 2 O (for CO insertion) and CH 3 C* + *CH 2 → CH 3 CH 2 C* (for CH 2 insertion).…”

“…Of particular interest is the analysis of C 2–4 hydrocarbon production using the Anderson–Schulz–Flory (ASF) equation, − ln­( w n / n ) = n ln α + constant, where n is the carbon number ( y -axis), w n is the mass fraction of a hydrocarbon product, and α is the hydrocarbon chain growth probability. In Figure S4c,d and the inset of Figure d, the y -axis represents ln­( w n / n ), the x -axis represents the carbon number ( n ), and the slope corresponds to ln α.…”

“…Metallic Sb appeared after sputtering for the electrode after EC (Figure 9f2). This indicates that the overlaid species were metallic Sb covered by Sb 2 O 3 .The VB profiles became broader after EC tests (Figure 9e3 [39][40][41][42][43]45,55,56 Similarly, the two-electron process for formate is known to occur through CO 2 + H + + e − → OCHO* and OCHO* + e − → HCOO − . [35][36][37][38]47 The adsorption of two intermediate species, *COOH and *CHO*, determines the final products and is highly dependent on the nature of the developed electrodes and the experimental conditions.…”

“…The electrochemical active surface area (ECSA) was assessed by analyzing cyclic voltammetry (CV) curves in the non-Faradaic current ranges with increasing scan rates under CO 2 -saturated KHCO 3 conditions. 55 Two selected CV curves for the Ag 30 Sb 30 /Cu and Sb electrodes are presented in Figure 7a,7b, respectively. It is evident that the CV for Ag 30 Sb 30 /Cu widened with an increase in the scan rate, whereas that of bare Sb showed much less change.…”

“…For ECSA estimation, ECSA (cm −2 ) = C dl /C s was used, assuming a specific doublelayer capacitance (C s ) of 40 μF/cm 2 . 55 Impedance profiles were generated for the electrodes, and the Nyquist plot, which includes the imaginary (Z″) and real (Z′) parts, 12,41 is depicted in Figure 7e. A high-frequency intercept on the real (Z′) axis corresponds to the total Ohmic resistance (R s ), which includes intrinsic, electrical, and electrolyte resistances.…”