Through-Space Charge Interaction Substituent Effects in Molecular Catalysis Leading to the Design of the Most Efficient Catalyst of CO₂-to-CO Electrochemical Conversion

Abstract

The starting point of this study of through-space substituent effects on the catalysis of the electrochemical CO-to-CO conversion by iron(0) tetraphenylporphyrins is the linear free energy correlation between through-structure electronic effects and the iron(I/0) standard potential that we established separately. The introduction of four positively charged trimethylanilinium groups at the para positions of the tetraphenylporphyrin (TPP) phenyls results in an important positive deviation from the correlation and a parallel improvement of the catalytic Tafel plot. The assignment of this catalysis boosting effect to the Coulombic interaction of these positive charges with the negative charge borne by the initial Fe-CO adduct is confirmed by the negative deviation observed when the four positive charges are replaced by four negative charges borne by sulfonate groups also installed in the para positions of the TPP phenyls. The climax of this strategy of catalysis boosting by means of Coulombic stabilization of the initial Fe-CO adduct is reached when four positively charged trimethylanilinium groups are introduced at the ortho positions of the TPP phenyls. The addition of a large concentration of a weak acid-phenol-helps by cleaving one of the C-O bonds of CO. The efficiency of the resulting catalyst is unprecedented, as can be judged by the catalytic Tafel plot benchmarking with all presently available catalysts of the electrochemical CO-to-CO conversion. The maximal turnover frequency (TOF) is as high as 10 s and is reached at an overpotential of only 220 mV; the extrapolated TOF at zero overpotential is larger than 300 s. This catalyst leads to a highly selective formation of CO (practically 100%) in spite of the presence of a high concentration of phenol, which could have favored H evolution. It is also very stable, showing no significant alteration after more than 80 h of electrolysis.

Dinuclear Metal Synergistic Catalysis Boosts Photochemical CO2‐to‐CO Conversion

“…[5] In biological systems,many catalytic active centers of metalloenzymes are dinuclear metallic complexes, [6,7] such as heterometallic [NiFe 4 (OH)S 4 ]c luster-based carbon mon-oxide dehydrogenase (CODHs), dinuclear-Fe II -based hydrogenase,d inuclear-Cu II -based tyrosinase and laccase,d inuclear-Zn II -based alkaline phosphatase,d inuclear-Cu-Zn bovine superoxide dismutase.B ye xploiting metal-metal cooperativity to accomplish different substrate recognition and transformation, these metalloenzymes undertake diverse physiologic functions in life system. [15][16][17] Thes olar-driven reduction of CO 2 into chemical fuels/ feedstocks represents ap otential strategy for solving the issues of energy crisis and global warming caused by increasing CO 2 emission. [8][9][10][11][12][13][14] In addition, it has been found that the addition of Lewis acidic metal cations to the mononuclear metal electrocatalysts can lower the overpotentials and subsequently increase the activities for the electrocatalytic CO 2 reduction.…”

“…Ther esults show that one single photoredox cycle produces 8.10 mmol of CO and 0.16 mmol of H 2 within 10 h ( Table 1, Entry 1; Figure 2a), along with trace amount of formate detected in the liquid phase by ion chromatograph (IC). [18] Moreover,w hen the [15][16][17] the experiments of photocatalytic CO 2 reduction by CoCo and Co in the presence of Zn II were performed. This TONvalue is 4-, 19-, and 45-fold higher than those of CoCo (17 000), ZnZn (3400), and Co (1500) under the same conditions (Table 1, entry 2-4; Figure 2b).…”

Bio-inspired CO2reduction by a rhenium tricarbonyl bipyridine-based catalyst appended to amino acids and peptidic platforms: incorporating proton relays and hydrogen-bonding functional groups

“…34 Other work has focused on incorporating proton sources directly into the ligand framework. 33,35 Previously, we have shown that the use of hydrogen-bonding motifs and amino acid residues can switch the dominant catalytic pathway for CO 2 reduction from a unimolecular one to a bimolecular one. 36 This change lowers the observed catalytic potential by ~250 mV.…”

Composition Tailoring via N and S Co‐doping and Structure Tuning by Constructing Hierarchical Pores: Metal‐Free Catalysts for High‐Performance Electrochemical Reduction of CO2

“…400 cm 2 membrane in as ingle process) is reported. [6][7][8][9][10][11][12][13][14][15] However,these traditional Notably, CO with 94 %F aradaic efficiency and À103 mA cm À2 current density are readily achieved with only about 1.2 mg catalyst loading, which are among the best results ever obtained by metal-free CO 2 RR catalysts.O nt he basis of control experiments and DFT calculations,s uch outstanding CO Faradaic efficiency can be attributed to the co-doped pyridinic Na nd carbon-bonded Sa toms,w hiche ffectively decrease the Gibbs free energy of key *COOH intermediate.F urthermore,h ierarchically porous structures of NSHCF membranes impart am uchh igher density of accessible active sites for CO 2 RR, leading to the ultra-high current density.…”

“…This is because CO 2 reduction can be readily conducted in aqueous solution, electrically driven from renewable energy sources,a nd produce value-added fuels or chemicals. [6][7][8][9][10][11][12][13][14][15] However,these traditional [4,5] Thep ast decades have witnessed metals (such as Ag, [6] Pd, [7] Au, [8] Co [9] )a nd their derivatives (that is,m etal oxides and metal complexes) as the most commonly used electrocatalysts for efficient CO 2 RR.…”