Abstract:Electrocatalytic reduction of CO2 to CO could represent the first step in solar-driven recycling of CO2 to fuels. While many reports focus on catalyst design or modification of additives such as Lewis or Brønsted acids, there is little focus on modification of the substrate, CO2 itself. Current carbon capture technology employs amines to capture CO2 as carbamates, suggesting that they may serve as a CO2 surrogate, streamlining carbon capture and recycling. Towards this, herein we explore the cyclic voltammetry… Show more
“… Figure 4 Electrochemical CO 2 reduction with amines in nonaqueous solution (A) Schematic (top) and cyclic voltammograms (CV, bottom) on carbon with 0.1 M EEA-CO 2 and 0.3 M LiClO 4 /DMSO ( Khurram et al., 2018 ). (B) Schematic (top) and CVs (bottom) using glassy carbon with 0.1 M amine-CO 2 , 0.1 M 1,1,3,3-tetramethylgunaidine (TMG) in 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6 ) in acetonitrile at 0.1 V s −1 ( Bhattacharya et al., 2020b ). (C) Schematic (top) and CV (bottom) using a Pb electrode with 1 M AMP-CO 2 in 0.7 M TEACl/PC ( Pérez-Gallent et al., 2021 ).…”
Section: Exemplar Processesmentioning
confidence: 99%
“… (B) Schematic (top) and CVs (bottom) using glassy carbon with 0.1 M amine-CO 2 , 0.1 M 1,1,3,3-tetramethylgunaidine (TMG) in 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6 ) in acetonitrile at 0.1 V s −1 ( Bhattacharya et al., 2020b ). …”
Section: Exemplar Processesmentioning
confidence: 99%
“…Bhattacharya et al. reported cyclic voltammetry of amines such as aniline, morpholine, diethylamine (DEA), triethylamine (TEA), and triethanolamine (TEOA) bound to CO 2 in acetonitrile with TBAPF 6 salt, and found that reductive activity was observed only in the presence of CO 2 ( Figure 4 B) ( Bhattacharya et al., 2020b ). Under bulk electrolysis conditions, formate (HCOO − ) was the only product, with neither CO nor H 2 detected.…”
Section: Exemplar Processesmentioning
confidence: 99%
“…Electrochemically reactive capture has so far been found capable of yielding a range of products depending on the electrolyte medium, such as carbon monoxide (CO) ( Chen et al., 2017 ; Abdinejad et al., 2020 ; Hossain et al., 2021 ; Lee et al., 2021 ; Pérez-Gallent et al., 2021 ), formate (HCOO − ) ( Chen et al., 2017 ; Bhattacharya et al., 2020b ; Pérez-Gallent et al., 2021 ), and solid alkali carbonates ( Khurram et al., 2018 ), often with high selectivity. Although prior studies have now demonstrated basic scientific feasibility, given the early stage of the field, influential parameters and rate-limiting factors have not yet been thoroughly studied, and rational design of such processes is not yet possible.…”
“… Figure 4 Electrochemical CO 2 reduction with amines in nonaqueous solution (A) Schematic (top) and cyclic voltammograms (CV, bottom) on carbon with 0.1 M EEA-CO 2 and 0.3 M LiClO 4 /DMSO ( Khurram et al., 2018 ). (B) Schematic (top) and CVs (bottom) using glassy carbon with 0.1 M amine-CO 2 , 0.1 M 1,1,3,3-tetramethylgunaidine (TMG) in 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6 ) in acetonitrile at 0.1 V s −1 ( Bhattacharya et al., 2020b ). (C) Schematic (top) and CV (bottom) using a Pb electrode with 1 M AMP-CO 2 in 0.7 M TEACl/PC ( Pérez-Gallent et al., 2021 ).…”
Section: Exemplar Processesmentioning
confidence: 99%
“… (B) Schematic (top) and CVs (bottom) using glassy carbon with 0.1 M amine-CO 2 , 0.1 M 1,1,3,3-tetramethylgunaidine (TMG) in 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6 ) in acetonitrile at 0.1 V s −1 ( Bhattacharya et al., 2020b ). …”
Section: Exemplar Processesmentioning
confidence: 99%
“…Bhattacharya et al. reported cyclic voltammetry of amines such as aniline, morpholine, diethylamine (DEA), triethylamine (TEA), and triethanolamine (TEOA) bound to CO 2 in acetonitrile with TBAPF 6 salt, and found that reductive activity was observed only in the presence of CO 2 ( Figure 4 B) ( Bhattacharya et al., 2020b ). Under bulk electrolysis conditions, formate (HCOO − ) was the only product, with neither CO nor H 2 detected.…”
Section: Exemplar Processesmentioning
confidence: 99%
“…Electrochemically reactive capture has so far been found capable of yielding a range of products depending on the electrolyte medium, such as carbon monoxide (CO) ( Chen et al., 2017 ; Abdinejad et al., 2020 ; Hossain et al., 2021 ; Lee et al., 2021 ; Pérez-Gallent et al., 2021 ), formate (HCOO − ) ( Chen et al., 2017 ; Bhattacharya et al., 2020b ; Pérez-Gallent et al., 2021 ), and solid alkali carbonates ( Khurram et al., 2018 ), often with high selectivity. Although prior studies have now demonstrated basic scientific feasibility, given the early stage of the field, influential parameters and rate-limiting factors have not yet been thoroughly studied, and rational design of such processes is not yet possible.…”
“…11,[16][17][18][19][20][21][22] Indeed, recent advances in molecular photocatalysis for the carbon dioxide reduction reaction (CO2RR) include metal-dependent enhancement of organic photosensitizers, 20,23 the use of hydrogen bonding, 24 electrostatic, 14,25,26 or covalent 27 interactions between photosensitizer and catalyst to improve electron transfer, and additives to increase CO2 solubility. [28][29][30][31][32] In terms of new catalyst design, first-row transition metal complexes supported by polypyridyl ligand frameworks 30, have emerged as privileged scaffolds for CO2RR. For example, we recently found that strong metal-ligand exchange coupling between an iron center and pentadentate polypyridyl ligand (tpyPY2Me) promotes its facile two-electron reduction to yield a reduced diamagnetic complex, [Fe(tpyPY2Me)] ([Fe] 0 ), which we assigned to an openshell singlet ground state that is composed of an intermediate-spin Fe 2+ center antiferromagnetically coupled to a doubly-reduced triplet tpyPY2Me ligand.…”
Catalyst platforms that promote multielectron charge delocalization offer an attractive approach to achieving the CO2 reduction reaction (CO2RR) with selectivity over the competing hydrogen evolution reaction (HER). Here, we show the importance of metal-ligand exchange coupling as an example of charge delocalization that can determine efficiency for photocatalytic CO2RR. A comparative evaluation of iron and cobalt complexes supported by the redox-active ligand tpyPY2Me establishes that the two-electron reduction of [Co(tpyPY2Me)]2+ ([Co]2+) occurs at potentials 770 mV more negative than the [Fe(tpyPY2Me)]2+ ([Fe]2+) analog by maximizing exchange coupling in the latter compound. The positive shift in reduction potential promoted by metal-ligand exchange coupling drives [Fe]2+ to be among the most active and selective molecular catalysts for photochemical CO2RR reported to date, maintaining up to 99% CO product selectivity with total turnover numbers (TON) and initial turnover frequencies (TOF) exceeding 30,000 and 900 min–1, respectively. In contrast, [Co]2+ shows much lower CO2RR activity, reaching only ca. 600 TON at 83% CO product selectivity under similar conditions accompanied by rapid catalyst decomposition. Spin density plots of the two-electron reduced [Co]0 complex implicate a paramagnetic open-shell doublet ground state compared to the diamagnetic open-shell singlet ground state of reduced [Fe]0, rationalizing the observed negative shift in two-electron reduction potentials from the [M]2+ species and lowered CO2RR efficiency for the cobalt complex relative to its iron congener. This work emphasizes the contributions of multielectron metal-ligand exchange coupling in promoting effective CO2RR and provides a starting point for the broader incorporation of this strategy in catalyst design.
Coupling renewable energy with the electrochemical conversion of CO 2 to chemicals and fuels has been proposed as a strategy to achieve a new circular carbon economy and help mitigate the effects of anthropogenic CO 2 emissions. Liquid-like Nanoparticle Organic Hybrid Materials (NOHMs) are composed of polymers tethered to nanoparticles and are previously explored as CO 2 capture materials and electrolyte additives. In this study, two types of aqueous NOHM-based electrolytes are prepared to explore the effect of CO 2 binding energy (i.e., chemisorption versus physisorption) on CO 2 electroreduction over a silver nanoparticle catalyst for syngas production. Poly(ethylenimine) (PEI) and Jeffamine M2070 (HPE) are ionically tethered to SiO 2 nanoparticles to form the amine-containing NOHM-I-PEI and ether-containing NOHM-I-HPE, respectively. At less negative cathode potentials, PEI and NOHM-I-PEI-based electrolytes produce CO at higher rates than 0.1 molal. KHCO 3 due to favorable catalyst-electrolyte interactions. Whereas at more negative potentials, H 2 production is favored because of the carbamate electrochemical inactivity. Conversely, HPE and NOHM-I-HPEbased electrolytes display poor CO 2 reduction performance at less negative potentials. At more negative potentials, their performance approached that of 0.1 molal. KHCO 3 , highlighting how the polymer functional groups of NOHMs can be strategically selected to produce value-added products from CO 2 with highly tunable compositions.
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