Promoting CO2 methanation via ligand-stabilized metal oxide clusters as hydrogen-donating motifs

AbstractElectroreduction uses renewable energy to upgrade carbon dioxide to value-added chemicals and fuels. Renewable methane synthesized using such a route stands to be readily deployed using existing infrastructure for the distribution and utilization of natural gas. Here we design a suite of ligand-stabilized metal oxide clusters and find that these modulate carbon dioxide reduction pathways on a copper catalyst, enabling thereby a record activity for methane electroproduction. Density functional theory calculations show adsorbed hydrogen donation from clusters to copper active sites for the *CO hydrogenation pathway towards *CHO. We promote this effect via control over cluster size and composition and demonstrate the effect on metal oxides including cobalt(II), molybdenum(VI), tungsten(VI), nickel(II) and palladium(II) oxides. We report a carbon dioxide-to-methane faradaic efficiency of 60% at a partial current density to methane of 135 milliampere per square centimetre. We showcase operation over 18 h that retains a faradaic efficiency exceeding 55%.

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Synthesis of Valeric Acid by Selective Electrocatalytic Hydrogenation of Biomass-Derived Levulinic Acid

Catalysts ◽

10.3390/catal10060692 ◽

2020 ◽

Vol 10 (6) ◽

pp. 692

Author(s):

Yan Du ◽

Xiao Chen ◽

Ji Qi ◽

Pan Wang ◽

Changhai Liang

Keyword(s):

Levulinic Acid ◽

Active Sites ◽

Valeric Acid ◽

Future Research ◽

Adsorbed Hydrogen ◽

Electrocatalytic Hydrogenation ◽

Ambient Conditions ◽

Metallic Lead ◽

Faradaic Efficiency ◽

Lead Electrode

The electrocatalytic hydrogenation (ECH) of biomass-derived levulinic acid (LA) is a promising strategy to synthetize fine chemicals under ambient conditions by replacing the thermocatalytic hydrogenation at high temperature and high pressure. Herein, various metallic electrodes were investigated in the ECH of LA in a H-type divided cell. The effects of potential, electrolyte concentration, reactant concentration, and temperature on catalytic performance and Faradaic efficiency were systematically explored. The high conversion of LA (93%) and excellent “apparent” selectivity to valeric acid (VA) (94%) with a Faradaic efficiency of 46% can be achieved over a metallic lead electrode in 0.5 M H2SO4 electrolyte containing 0.2 M LA at an applied voltage of −1.8 V (vs. Ag/AgCl) for 4 h. The combination of adsorbed LA and adsorbed hydrogen (Hads) on the surface of the metallic lead electrode is key to the formation of VA. Interestingly, the reaction performance did not change significantly after eight cycles, while the surface of the metallic lead cathode became rough, which may expose more active sites for the ECH of LA to VA. However, there was some degree of corrosion for the metallic lead cathode in this strong acid environment. Therefore, it is necessary to improve the leaching-resistance of the cathode for the ECH of LA in future research.

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A comparative study of small 3d-metal oxide (FeO)n, (CoO)n, and (NiO)n clusters

Physical Chemistry Chemical Physics ◽

10.1039/c6cp03241a ◽

2016 ◽

Vol 18 (40) ◽

pp. 27858-27867 ◽

Cited By ~ 11

Author(s):

G. L. Gutsev ◽

K. G. Belay ◽

K. V. Bozhenko ◽

L. G. Gutsev ◽

B. R. Ramachandran

Keyword(s):

Density Functional Theory ◽

Metal Oxide ◽

Comparative Study ◽

Electronic Structures ◽

Density Functional ◽

Generalized Gradient ◽

Functional Theory ◽

Metal Oxide Clusters ◽

Generalized Gradient Approximation

Geometrical and electronic structures of the 3d-metal oxide clusters (FeO)n, (CoO)n, and (NiO)n are computed using density functional theory with the generalized gradient approximation in the range of 1 ≤ n ≤ 10.

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How Stable Are 2H-MoS2 Edges Under Hydrogen Evolution Reaction Conditions?

10.26434/chemrxiv.14711007.v1 ◽

2021 ◽

Author(s):

Nawras Abidi ◽

Audrey Bonduelle-Skrzypczak ◽

Stephan Steinmann

Keyword(s):

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Active Sites ◽

Density Functional ◽

External Source ◽

Operating Conditions ◽

Adsorbed Hydrogen ◽

Functional Theory ◽

Acidic Conditions

MoS2, have emerged as a promising class of electrocatalysts for the production of H2 via the hydrogen evolution reaction (HER) in acidic conditions.<div>The edges of MoS2 are known for their HER activity, but their precise atomistic nature and stability under HER conditions is not yet known. In contrast to other typical uses of MoS2 as a catalyst, under HER there is no external source of sulfur. Therefore, the sulfidation of the edges can only decrease under operating conditions and the thermodynamics of the process are somewhat ill-defined. Our results suggest that the 50%S S-edge may be active for HER via the Volmer-Tafel mechanism and is, despite a high H coverage, stable with respect to H2S release. </div><div>At the 50%S Mo-edge, the adsorbed hydrogen opens the way for H2S release, leading to the 0%S Mo-edge, which was previously investigated and found to be HER active. HER being a water-based process, we also considered the effect of the presence of H2O and the in-situ formation of OH. For the 50%S Mo-edge, H2O is only very weakly adsorbed and OH formation is unfavorable. Nevertheless, OH assists the loss of sulfur coverage, leading to OH-based HER active sites. In contrast, OH is strongly adsorbed on the 50%S S-edge. By explicitly considering the electrochemical potential using grand-canonical density functional theory, we unveil that the Volmer-Heyrovsky mechanism on sulfur sites is still accessible in the presence of surface OH at the 50%S S-edge. However, the 50%S S-edge is found to be mildly unstable with respect to H2S in the presence of water/OH. Hence, we suggest that the 50%S S-edge evolves over time towards a 0%S S-edge, covered by surface OH that will block permanently the active sites. </div>

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Electro-reduction of carbon dioxide at low over-potential at a metal–organic framework decorated cathode

Nature Communications ◽

10.1038/s41467-020-19236-4 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Xinchen Kang ◽

Lili Li ◽

Alena Sheveleva ◽

Xue Han ◽

Jiangnan Li ◽

...

Keyword(s):

Carbon Dioxide ◽

Formic Acid ◽

Active Sites ◽

Metal Organic Framework ◽

Computational Modelling ◽

Structural Defects ◽

Resonance Spectroscopy ◽

Faradaic Efficiency ◽

Metal Organic ◽

Organic Framework

Abstract Electrochemical reduction of carbon dioxide is a clean and highly attractive strategy for the production of organic products. However, this is hindered severely by the high negative potential required to activate carbon dioxide. Here, we report the preparation of a copper-electrode onto which the porous metal–organic framework [Cu2(L)] [H4L = 4,4′,4″,4′′′-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzoic acid] can be deposited by electro-synthesis templated by an ionic liquid. This decorated electrode shows a remarkable onset potential for reduction of carbon dioxide to formic acid at −1.45 V vs. Ag/Ag+, representing a low value for electro-reduction of carbon dioxide in an organic electrolyte. A current density of 65.8 mA·cm−2 at −1.8 V vs. Ag/Ag+ is observed with a Faradaic efficiency to formic acid of 90.5%. Electron paramagnetic resonance spectroscopy confirms that the templated electro-synthesis affords structural defects in the metal–organic framework film comprising uncoupled Cu(II) centres homogenously distributed throughout. These active sites promote catalytic performance as confirmed by computational modelling.

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Alkaline Earth Metal Oxide Nanocluster Modification of Rutile TiO2 (110) Promotes Water Activation and CO2 Chemisorption

10.26434/chemrxiv.5909833.v1 ◽

2018 ◽

Author(s):

Michael Nolan

Keyword(s):

Metal Oxide ◽

Visible Light ◽

Light Absorption ◽

Environmental Remediation ◽

Active Sites ◽

Density Functional ◽

Alkaline Earth ◽

Earth Metal ◽

Alkaline Earth Metal ◽

Alkaline Earth Oxide

Metal oxide photocatalysts are widely studied for applications in solar driven environmental remediation, antimicrobial activity, hydrogen production and CO2 reduction to fuels. Common requirements for each technology include absorption of visible light, reduced charge carrier recombination and the ability to activate the initial molecule be it a pollutant, water or CO2. The leading photocatalyst is some form of TiO2. A significant amount of work has been undertaken to modifying TiO2 to induce visible light absorption. The structure and composition of the catalyst should facilitate separation of electrons and holes and having active sites on the catalyst is important to promote the initial adsorption and activation of molecules of interest. In this paper we present a first principles density functional theory (DFT) study of the modification of rutile TiO2 (110) with nanoclusters of the alkaline earth metal oxides (MgO, Ca, BaO) and we focus on the effect of surface modification on the key catalyst properties. The modification of rutile TiO2 with CaO and BaO induces a predicted red shift in light absorption. In all cases, photoexcited electrons and holes localise on oxygen in the nanocluster and surface Ti sites, thus enhancing charge separation. The presence of these non-bulk alkaline earth oxide nanoclusters provides highly active sites for water and CO2 adsorption. On MgO-rutile, water adsorbs molecularly and overcomes a barrier of only 0.36 eV for dissociation whereby hydroxyls are stabilised. On CaO- and BaO-modified rutile water adsorbs dissociatively. We attribute this to the high lying O 2p states in the alkaline earth oxide modifiers which are available to interact with water, as well as the non-bulk like geometry around the active site. Upon adsorption of CO2 the preferred binding mode is as a tridentate carbonate-like species, as characterised by geometry and vibrational modes. The carbonate is bound by up to 4 eV. Thus these heterostructures can be interesting for CO2 capture, helping alleviate the problem of CO2 emissions.

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Electrochemical Biomass Valorization on Gold-Metal Oxide Nanoscale Heterojunctions Enables Investigation of both Catalyst and Reaction Dynamics with Operando Surface-Enhanced Raman Spectroscopy

10.26434/chemrxiv.10287534 ◽

2019 ◽

Author(s):

Nina Heidary ◽

Nikolay Kornienko

Keyword(s):

Metal Oxide ◽

Water Oxidation ◽

Value Added ◽

High Water ◽

Surface Enhanced Raman Spectroscopy ◽

Oxidation Activity ◽

Faradaic Efficiency ◽

Surface Enhanced ◽

Surface Enhanced Raman ◽

Gold Metal

The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging clean technology. However, mechanistic knowledge of this reaction in an electrochemical context is still lacking and operando studies are even more rare. In this work, we utilize core-shell gold-metal oxide nanostructures which enable operando surface-enhanced Raman spectroelectrochemical studies to simultaneously visualize catalyst material transformation and surface reaction intermediates under an applied voltage. As a case study, we show how the transformation of NiOOH from ~1-2 nm amorphous Ni layers facilitates the onset of HMF oxidation to 2,5-furandicarboxylic acid (FDCA), which is attained with near 100% Faradaic efficiency in 1M KOH. In contrast to the case in 1M KOH, NiOOH formation is suppressed, and consequently HMF oxidation is sluggish 10 mM KOH, even at high potentials. Operando Raman experiments elucidate how surface adsorption and interaction dictates product selectivity and how the surface intermediates evolve with applied potential. We further extend our methodology to investigate NiFe, Co, Fe, and CoFe catalysts and demonstrate that high water oxidation activity is not necessarily correlated with excellent HMF oxidation performance and highlight catalytic factors important for this reaction such as reactant-surface interactions and catalysts’ physical and electronic structure.

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Elucidation of the Roles of Ionic Liquid in CO2 Electrochemical Reduction to Value-Added Chemicals and Fuels

Molecules ◽

10.3390/molecules26226962 ◽

2021 ◽

Vol 26 (22) ◽

pp. 6962

Author(s):

Sulafa Abdalmageed Saadaldeen Mohammed ◽

Wan Zaireen Nisa Yahya ◽

Mohamad Azmi Bustam ◽

Md Golam Kibria

Keyword(s):

Carbon Dioxide ◽

Ionic Liquids ◽

Reaction Mechanism ◽

Electrochemical Reduction ◽

Value Added ◽

Faradaic Efficiency ◽

Renewable Source ◽

Carbon Dioxide Co2 ◽

Physical And Chemical ◽

Value Added Products

The electrochemical reduction of carbon dioxide (CO2ER) is amongst one the most promising technologies to reduce greenhouse gas emissions since carbon dioxide (CO2) can be converted to value-added products. Moreover, the possibility of using a renewable source of energy makes this process environmentally compelling. CO2ER in ionic liquids (ILs) has recently attracted attention due to its unique properties in reducing overpotential and raising faradaic efficiency. The current literature on CO2ER mainly reports on the effect of structures, physical and chemical interactions, acidity, and the electrode–electrolyte interface region on the reaction mechanism. However, in this work, new insights are presented for the CO2ER reaction mechanism that are based on the molecular interactions of the ILs and their physicochemical properties. This new insight will open possibilities for the utilization of new types of ionic liquids. Additionally, the roles of anions, cations, and the electrodes in the CO2ER reactions are also reviewed.

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Highly efficient binary copper−iron catalyst for photoelectrochemical carbon dioxide reduction toward methane

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1911159117 ◽

2020 ◽

Vol 117 (3) ◽

pp. 1330-1338 ◽

Cited By ~ 9

Author(s):

Baowen Zhou ◽

Pengfei Ou ◽

Nick Pant ◽

Shaobo Cheng ◽

Srinivas Vanka ◽

...

Keyword(s):

Carbon Dioxide ◽

Density Functional ◽

Rational Design ◽

Iron Catalyst ◽

High Current Density ◽

Density Functional Theory Calculations ◽

High Energy ◽

Faradaic Efficiency ◽

High Energy Barrier ◽

Linear Configuration

A rational design of an electrocatalyst presents a promising avenue for solar fuels synthesis from carbon dioxide (CO2) fixation but is extremely challenging. Herein, we use density functional theory calculations to study an inexpensive binary copper−iron catalyst for photoelectrochemical CO2 reduction toward methane. The calculations of reaction energetics suggest that Cu and Fe in the binary system can work in synergy to significantly deform the linear configuration of CO2 and reduce the high energy barrier by stabilizing the reaction intermediates, thus spontaneously favoring CO2 activation and conversion for methane synthesis. Experimentally, the designed CuFe catalyst exhibits a high current density of −38.3 mA⋅cm−2 using industry-ready silicon photoelectrodes with an impressive methane Faradaic efficiency of up to 51%, leading to a distinct turnover frequency of 2,176 h−1 under air mass 1.5 global (AM 1.5G) one-sun illumination.

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Fast operando spectroscopy tracking in situ generation of rich defects in silver nanocrystals for highly selective electrochemical CO2 reduction

Nature Communications ◽

10.1038/s41467-021-20960-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Xinhao Wu ◽

Yanan Guo ◽

Zengsen Sun ◽

Fenghua Xie ◽

Daqin Guan ◽

...

Keyword(s):

Active Sites ◽

Density Functional ◽

Co2 Reduction ◽

Density Functional Theory Calculations ◽

Defect Concentration ◽

Hydrogen Electrode ◽

Efficient Catalyst ◽

Faradaic Efficiency ◽

Electrochemical Co2 Reduction ◽

Cell Reactor

AbstractElectrochemical CO2 reduction (ECR) is highly attractive to curb global warming. The knowledge on the evolution of catalysts and identification of active sites during the reaction is important, but still limited. Here, we report an efficient catalyst (Ag-D) with suitable defect concentration operando formed during ECR within several minutes. Utilizing the powerful fast operando X-ray absorption spectroscopy, the evolving electronic and crystal structures are unraveled under ECR condition. The catalyst exhibits a ~100% faradaic efficiency and negligible performance degradation over a 120-hour test at a moderate overpotential of 0.7 V in an H-cell reactor and a current density of ~180 mA cm−2 at −1.0 V vs. reversible hydrogen electrode in a flow-cell reactor. Density functional theory calculations indicate that the adsorption of intermediate COOH could be enhanced and the free energy of the reaction pathways could be optimized by an appropriate defect concentration, rationalizing the experimental observation.

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Silica-copper catalyst interfaces enable carbon-carbon coupling towards ethylene electrosynthesis

Nature Communications ◽

10.1038/s41467-021-23023-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jun Li ◽

Adnan Ozden ◽

Mingyu Wan ◽

Yongfeng Hu ◽

Fengwang Li ◽

...

Keyword(s):

Active Sites ◽

Density Functional ◽

Copper Catalyst ◽

Scale Up ◽

Coupling Reaction ◽

Density Functional Theory Calculations ◽

Membrane Electrode Assembly ◽

Membrane Electrode ◽

One Pot ◽

Sustained Operation

AbstractMembrane electrode assembly (MEA) electrolyzers offer a means to scale up CO2-to-ethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. To date, excessive CO2 coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. With the aid of density functional theory calculations and spectroscopic analysis, here we report an oxide modulation strategy in which we introduce silica on Cu to create active Cu-SiOx interface sites, decreasing the formation energies of OCOH* and OCCOH*—key intermediates along the pathway to ethylene formation. We then synthesize the Cu-SiOx catalysts using one-pot coprecipitation and integrate the catalyst in a MEA electrolyzer. By tuning the CO2 concentration, the Cu-SiOx catalyst based MEA electrolyzer shows high ethylene Faradaic efficiencies of up to 65% at high ethylene current densities of up to 215 mA cm−2; and features sustained operation over 50 h.

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