scholarly journals An Iron Pyridyl-Carbene Catalyst for Low Overpotential CO2 reduction to CO: Mechanistic Comparisons with the Ruthenium Analogue and Photochemical Promotion

2020 ◽  
Author(s):  
Sergio Gonell ◽  
Julio Lloret ◽  
Alexander Miller
Keyword(s):  
Co2 Reduction ◽  
Iron Complexes ◽  
Transition Metal Ions ◽  
Ruthenium Catalysts ◽  
Computational Studies ◽  
Chelating Ligands ◽  
Faradaic Efficiency ◽  
Mechanistic Insight ◽  
Redox Active ◽  
Improved Performance

<div><div><div><p>Electrocatalysts for CO2 reduction based on first row transition metal ions have attracted attention as abundant and affordable candidates for energy conversion applications. We hypothesized that a successful strategy in ruthenium electrocatalyst design, featuring two chelating ligands that can be individually tuned to adjust the overpotential and catalytic activity, could be equally applicable in the analogous iron complexes. New iron complexes supported by a redox-active 2,2':6',2''-terpyridine (tpy) ligand and strong trans effect pyridyl- N-heterocyclic carbene ligand (1-methyl-benzimidazol-2-ylidene-3-(2-pyridine)) were synthesized, and these isostructural analogues to leading ruthenium catalysts were also found to be active CO2 reduction electrocatalysts. Electrochemical and computational studies reveal completely distinct mechanisms for the iron and ruthenium complexes, with hemilability in the iron system enabling electrocatalysis at overpotentials as low as 150 mV (ca. 500 mV lower than the ruthenium analogue). Cyclic voltammetry studies elucidated the mechanism of the net 4e–/2H+ process that occurs within the single reductive feature, with an iron solvento complex undergoing reduction, CO2 activation, and further reduction to an iron carbonyl. The mechanistic insight guided development of photoelectrocatalytic conditions under a continuous flow of CO2 that exhibited improved performance, with Faradaic efficiency up to 99%.</p></div></div></div>

scholarly journals An Iron Pyridyl-Carbene Catalyst for Low Overpotential CO2 reduction to CO: Mechanistic Comparisons with the Ruthenium Analogue and Photochemical Promotion

2020 ◽  
Author(s):  
Sergio Gonell ◽  
Julio Lloret ◽  
Alexander Miller
Keyword(s):  
Co2 Reduction ◽  
Iron Complexes ◽  
Transition Metal Ions ◽  
Ruthenium Catalysts ◽  
Computational Studies ◽  
Chelating Ligands ◽  
Faradaic Efficiency ◽  
Mechanistic Insight ◽  
Redox Active ◽  
Improved Performance

<div><div><div><p>Electrocatalysts for CO2 reduction based on first row transition metal ions have attracted attention as abundant and affordable candidates for energy conversion applications. We hypothesized that a successful strategy in ruthenium electrocatalyst design, featuring two chelating ligands that can be individually tuned to adjust the overpotential and catalytic activity, could be equally applicable in the analogous iron complexes. New iron complexes supported by a redox-active 2,2':6',2''-terpyridine (tpy) ligand and strong trans effect pyridyl- N-heterocyclic carbene ligand (1-methyl-benzimidazol-2-ylidene-3-(2-pyridine)) were synthesized, and these isostructural analogues to leading ruthenium catalysts were also found to be active CO2 reduction electrocatalysts. Electrochemical and computational studies reveal completely distinct mechanisms for the iron and ruthenium complexes, with hemilability in the iron system enabling electrocatalysis at overpotentials as low as 150 mV (ca. 500 mV lower than the ruthenium analogue). Cyclic voltammetry studies elucidated the mechanism of the net 4e–/2H+ process that occurs within the single reductive feature, with an iron solvento complex undergoing reduction, CO2 activation, and further reduction to an iron carbonyl. The mechanistic insight guided development of photoelectrocatalytic conditions under a continuous flow of CO2 that exhibited improved performance, with Faradaic efficiency up to 99%.</p></div></div></div>

scholarly journals Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ji-Yong Kim ◽  
Deokgi Hong ◽  
Jae-Chan Lee ◽  
Hyoung Gyun Kim ◽  
Sungwoo Lee ◽  
...  
Keyword(s):  
High Efficiency ◽  
Co2 Reduction ◽  
Value Added ◽  
Material Design ◽  
Catalyst System ◽  
Critical Issue ◽  
Reduction Reaction ◽  
Catalyst Design ◽  
Design Strategies ◽  
Faradaic Efficiency

AbstractFor steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas–solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at −0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.

scholarly journals A high throughput optical method for studying compositional effects in electrocatalysts for CO2 reduction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jeremy L. Hitt ◽  
Yuguang C. Li ◽  
Songsheng Tao ◽  
Zhifei Yan ◽  
Yue Gao ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
High Throughput ◽  
High Throughput Screening ◽  
Screening Method ◽  
Co2 Reduction ◽  
Fold Increase ◽  
Faradaic Efficiency ◽  
Atomic Pair Distribution Function ◽  
Earth Abundant ◽  
Ternary Catalysts

AbstractIn the problem of electrochemical CO2 reduction, the discovery of earth-abundant, efficient, and selective catalysts is essential to enabling technology that can contribute to a carbon-neutral energy cycle. In this study, we adapt an optical high throughput screening method to study multi-metallic catalysts for CO2 electroreduction. We demonstrate the utility of the method by constructing catalytic activity maps of different alloyed elements and use X-ray scattering analysis by the atomic pair distribution function (PDF) method to gain insight into the structures of the most active compositions. Among combinations of four elements (Au, Ag, Cu, Zn), Au6Ag2Cu2 and Au4Zn3Cu3 were identified as the most active compositions in their respective ternaries. These ternary electrocatalysts were more active than any binary combination, and a ca. 5-fold increase in current density at potentials of −0.4 to −0.8 V vs. RHE was obtained for the best ternary catalysts relative to Au prepared by the same method. Tafel plots of electrochemical data for CO2 reduction and hydrogen evolution indicate that the ternary catalysts, despite their higher surface area, are poorer catalysts for the hydrogen evolution reaction than pure Au. This results in high Faradaic efficiency for CO2 reduction to CO.

scholarly journals CuZnAl-Oxide Nanopyramidal Mesoporous Materials for the Electrocatalytic CO2 Reduction to Syngas: Tuning of H2/CO Ratio

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3052
Author(s):  
Hilmar Guzmán ◽  
Daniela Roldán ◽  
Adriano Sacco ◽  
Micaela Castellino ◽  
Marco Fontana ◽  
...  
Keyword(s):  
Noble Metals ◽  
Co2 Reduction ◽  
Reduction Process ◽  
Mesoporous Structure ◽  
Catalytic Performance ◽  
H2 Production ◽  
Ambient Conditions ◽  
Transfer Resistance ◽  
Faradaic Efficiency ◽  
Co2 Electroreduction

Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions.

Synthesis and Catalysis of Redox-Active Bis(imino)acenaphthene (BIAN) Iron Complexes

ChemCatChem ◽  
2017 ◽  
Vol 9 (16) ◽  
pp. 3203-3209 ◽  
Author(s):  
Matteo Villa ◽  
Dominique Miesel ◽  
Alexander Hildebrandt ◽  
Fabio Ragaini ◽  
Dieter Schaarschmidt ◽  
...  
Keyword(s):  
Iron Complexes ◽  
Redox Active

Mechanistic Insights into the Spontaneous Reaction Between CO2 and La2-xSrxCuO4

2021 ◽  
Author(s):  
Alexander William Henry Whittingham ◽  
Jordan Lau ◽  
Rodney David Lucien Smith
Keyword(s):  
Electrochemical Impedance ◽  
Co2 Reduction ◽  
Active Surface ◽  
Structural Instability ◽  
Redox Couple ◽  
Surface Sites ◽  
Carbonate Ions ◽  
Redox Active ◽  
Spontaneous Reaction

Layered perovskites such as La2-xSrxCuO4 are active electrocatalysts for CO2 reduction, but they suffer from structural instability under catalytic conditions. This structural instability is found to arise from the reaction of CO2 with surface sites. Variable scan rate voltammetry shows the growth of a Cu-based redox couple when potentials cathodic of 0.6 V vs. RHE are applied in the presence of CO2. Electrochemical impedance spectroscopy identifies a redox active surface state at this voltage, whose concentration is increased by electrochemical reduction in the presence of CO2. In-situ spectroelectrochemical FTIR identifies surface bound carbonates as being involved formation of these surface sites. The orthorhombic lattice for La2-xSrxCuO4 is found to uniquely enable monodentate binding of (bi)carbonate ions from solution as well as bidentate carbonate ions through reaction with CO2. The incorporation of Sr(II) induces a transition to a tetragonal lattice, for which only monodentate carbonate ions are observed. It is proposed that the binding of carbonate ions in a bidentate fashion generates sufficient strain at the surface to result in amorphization at the surface, yielding the observed Cu(II)/Cu(I) redox couple.

CO2 reduction to formic acid at low overpotential on BDD electrodes modified with nanostructured CeO2

2019 ◽  
Vol 7 (30) ◽  
pp. 17896-17905 ◽  
Author(s):  
Enrico Verlato ◽  
Simona Barison ◽  
Yasuaki Einaga ◽  
Stefano Fasolin ◽  
Marco Musiani ◽  
...  
Keyword(s):  
Formic Acid ◽  
Co2 Reduction ◽  
Faradaic Efficiency ◽  
Low Overpotential

Nanostructured CeO2/BDD electrodes produce formic acid with good faradaic efficiency at very low overpotential (>40% at η ≈ 40 mV).

Regulation of magnetic relaxation behavior by replacing 3d transition metal ions in [M2Dy2] complexes containing two different organic chelating ligands

2019 ◽  
Vol 48 (27) ◽  
pp. 10011-10022 ◽  
Author(s):  
Hui-Sheng Wang ◽  
Cheng-Ling Yin ◽  
Zhao-Bo Hu ◽  
Yong Chen ◽  
Zhi-Quan Pan ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Single Molecule ◽  
Magnetic Relaxation ◽  
Transition Metal Ions ◽  
Relaxation Behavior ◽  
Organic Ligands ◽  
Chelating Ligands ◽  
Single Molecule Magnet

Two [MIII2DyIII2] complexes (M = Fe for 1 and Co for 2) with mixed organic ligands were obtained. Complex 2 exhibits single molecule magnet behavior with Ueff = 64.0(9) K.

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