Electrochemical Conversion of Carbon Dioxide into CHO‐Containing Compounds on Multimetallic Porphyrins

Abstract

This work describes the electrochemical reduction of carbon dioxide in aqueous solution mediated by tetraruthenated metalloporphyrins (TRP; Co(II) and Zn(II)) in Nafion (Nf) and polyvinyl chloride (PVC) as a support. The comparative aspects of the two polymeric matrices are expressed in terms of the electrocatalytic behavior toward carbon dioxide reduction of both sets of modified electrodes; values of overpotential and turnover frequency were calculated in each case. The modified electrodes under survey were able to reduce carbon dioxide at −600 mV vs Ag/AgCl showing an enhanced reduction current and a decrease in the required overpotential compared to a bare glassy carbon (GC) electrode. Potential‐controlled electrolysis experiments were carried out at −1000 mV in order to compare the distribution of products. The production of formic acid, formaldehyde and methanol was confirmed at potentials where reduction of solvent may occur. Measurements of electrochemical impedance spectroscopy show the presence of one active site for GC/Nf/MTRP (where M=Zn(II) and Co(II)) and three for GC/PVC/MTRP. This information corroborates the high values of TOF obtained for GC/PVC/ZnTRP as the best electrocatalyst.

Reduced Graphene Oxide Overlayer on Copper Nanocube Electrodes Steers the Selectivity Towards Ethanol in Electrochemical Reduction of Carbon Dioxide

“…The semicircle at high frequency (see inset of Figure 5A) indicates the movement of ions inside the double layer. The other semicircle at intermediate‐low frequencies has capacitor characteristics, probably indicating the accumulation of gases in the electric double layer [31] …”

“…In the Bode plot, two relaxation time constants are observed in the high and low‐frequency zones that correspond to diffusion‐controlled charge storage sites [31] …”

“…The relevant data and the equivalent circuits, duly justified, are summarized in Supplementary Tables S2 and S3. The corresponding models used for fitting the EIS data are given in Schemes S1 and S2 of the supporting information, respectively [30–33] …”

“…The other semicircle at intermediate-low frequencies has capacitor characteristics, probably indicating the accumulation of gases in the electric double layer. [31] In the Bode plot, two relaxation time constants are observed in the high and low-frequency zones that correspond to diffusion-controlled charge storage sites. [31] The rGO-modified Cu NCbs catalysts exhibit similar behavior for the 60s and 120s rGOÀ NCbs electrodes, but their behavior is different from that of Cu NCbs, Figure 5C to F. The Nyquist diagram of Cu NCbsÀ rGO shows only one semicircle at a high frequency that would indicate the analogous process occurring on the Cu NCbs electrode surface, Figures 5C and E.…”

“…The corresponding models used for fitting the EIS data are given in Schemes S1 and S2 of the supporting information, respectively. [30][31][32][33] Figures 5 A and B show the Nyquist and Bode diagrams for the Cu nanocube electrode. The Nyquist and Bode diagrams for Cu NCbs in Ar and CO 2 atmosphere are similar, with two semicircles.…”