Catalysts For CO2 Reduction Research Articles

Tunable Selectivity of Photothermal CO2 Reduction over Composition‐Mediated Ni–Mo Alloy Catalysts

As a promising technology to mitigate global carbon emissions, photothermal catalytic CO2 reduction remains a great challenge in increasing the conversion efficiency and regulating the product selectivity. Herein, a series of phase‐separated Ni–Mo alloy catalysts for efficient photothermal CO2 reduction with tunable CO selectivity is reported. With the increase of Mo content, the evolution rate and selectivity of CO increases. The optimal catalyst Ni1Mo1 achieves 32.1% CO2 conversion with 98.0% of CO selectivity and 71.1 mmol gcat−1 h−1 of CO evolution rate under a 300 W xenon lamp irradiation. Further increasing the Mo content reduces the CO evolution rate while maintaining the high CO selectivity. In the mechanistic study, it is revealed that the Ni–Mo alloy with an appropriate Ni/Mo ratio (e.g., Ni1Mo1) possesses a modified electronic structure with more negative d‐band center, which increases the light absorption, reduces the H2 dissociation, and favors the CO desorption, thereby leading to efficient and selective photothermal reduction of CO2 to CO. In this work, a viable strategy to design nickel‐based catalysts is provided for efficient and selective photothermal CO2 reduction via composition‐mediated modification of electronic structure.

A comparison between 2D and 3D cobalt–organic framework as catalysts for electrochemical CO2 reduction

Electrocatalytic CO2 reduction, as an effective way to reduce the CO2 concentration, has gained attention. In this study, we prepared ZIF-67 nanoparticles and nanosheets and investigated them as electrocatalysts for CO2 reduction. It was found that ZIF-67 nanosheets, because of their two–dimensional morphologies, provide more under–coordinated cobalt nodes and have lower overpotentials for both hydrogen evolution and CO2 reduction reactions. Also, the rate–determining step for hydrogen evolution changes from Volmer for ZIF-67 nanoparticles to Hyrovsky for ZIF-67 nanosheets. Also, the presence of Mg2+ ions in solution causes more facile CO2 reduction, especially for ZIF-67 nanosheets.

Boosting Electrochemical CO2 Reduction on Copper-Based Metal-Organic Frameworks via Valence and Coordination Environment Modulation.

Cu-based metal-organic frameworks (MOFs) have attracted much attention for electrocatalytic CO2 reduction to high value-added chemicals, but they still suffer from low selectivity and instability. Here, an associative design strategy for the valence and coordination environment of the metal node in Cu-based MOFs is employed to regulate the CO2 electroreduction to ethylene. A novel "reduction-cleavage-recrystallization" method is developed to modulate the Cu(II)-Trimesic acid (BTC) framework to form a Cu(I)-BTC structure enriched with free carboxyl groups in the secondary coordination environment (SCE). In contrast to Cu(II)-BTC, the Cu(I)-BTC shows higher catalytic activity and better ethylene selectivity (≈2.2-fold) for CO2 electroreduction, which is further enhanced by increasing the content of free carboxyl groups, resulting in ethylene Faraday efficiency of up to 57% and the durability of the catalyst could last for 38h without performance decline. It indicates that the synergistic effect between Cu(I)-O coordinated structure and free carboxyl groups considerably enhances the dimerization of *CO intermediates and hinders the hydrogenation of *CO intermediates in these competitive pathways. This work unravels the strong dependence of CO2 electroreduction on the Cu valence state and coordination environment in MOFs and provides a platform for designing highly selective electrocatalytic CO2 reduction catalysts.

Prediction of M3 B4 -type MBenes as Promising Catalysts for CO2 Capture and Reduction.

The rational design of novel catalysts with high activity and selectivity for carbon dioxide reduction reaction (CO2 RR) is highly desired. In this work, we have extensive investigations on the properties of two-dimensional transition metal borides (MBenes) to achieve efficient CO2 capture and reduction through first-principles calculations. The results show that all the investigated M3 B4 -type MBene exhibit remarkable CO2 capture and activation abilities, which proved to be derived from the lone pair of electrons on the MBene surface. Then, we emphasize that the investigated MBenes can further selectively reduce activated CO2 to CH4 . Moreover, a new linear scaling relationship of the adsorption energies of potential-determining intermediates (*OCH2 O and *HOCH2 O) versus ΔG(*OCHO) has been established, where the CO2 RR limiting potentials on MBenes are determined by the different fitting slopes of ΔG(*OCH2 O) and ΔG(*HOCHO), allowing significantly lower limiting potentials to be achieved compared to transition metals. Especially, two promising CO2 RR catalysts (Mo3 B4 and Cr3 B4 MBene) exist quite low limiting potentials of -0.48 V and -0.66 V, as well as competitive selectivity concerning hydrogen evolution reactions have been identified. Our research results make future advances in CO2 capture by MBenes easier and exploit the applications of Mo3 B4 and Cr3 B4 MBenes as novel CO2 RR catalysts.

How Precisely Can Individual Molecules Be Analyzed? A Case Study on Locally Quantifying Forces and Energies Using Scanning Probe Microscopy.

Recent advances in scanning probe microscopy methodology have enabled the measurement of tip-sample interactions with picometer accuracy in all three spatial dimensions, thereby providing a detailed site-specific and distance-dependent picture of the related properties. This paper explores the degree of detail and accuracy that can be achieved in locally quantifying probe-molecule interaction forces and energies for adsorbed molecules. Toward this end, cobalt phthalocyanine (CoPc), a promising CO2 reduction catalyst, was studied on Ag(111) as a model system using low-temperature, ultrahigh vacuum noncontact atomic force microscopy. Data were recorded as a function of distance from the surface, from which detailed three-dimensional maps of the molecule's interaction with the tip for normal and lateral forces as well as the tip-molecule interaction potential were constructed. The data were collected with a CO molecule at the tip apex, which enabled a detailed visualization of the atomic structure. Determination of the tip-substrate interaction as a function of distance allowed isolation of the molecule-tip interactions; when analyzing these in terms of a Lennard-Jones-type potential, the atomically resolved equilibrium interaction energies between the CO tethered to the tip and the CoPc molecule could be recovered. Interaction energies peaked at less than 160 meV, indicating a physisorption interaction. As expected, the interaction was weakest at the aromatic hydrogens around the periphery of the molecule and strongest surrounding the metal center. The interaction, however, did not peak directly above the Co atom but rather in pockets surrounding it.

Empowering the Nickel Iron Oxyhydroxide through a Heterostructure Cocatalyst for Superior Alkaline and Saline Water Reduction

Empowering the Nickel Iron Oxyhydroxide through a Heterostructure Cocatalyst for Superior Alkaline and Saline Water Reduction

Stabilizing *CO2 Intermediates at the Acidic Interface using Molecularly Dispersed Cobalt Phthalocyanine as Catalysts for CO2 Reduction.

CO2 electroreduction (CO2 R) operating in acidic media circumvents the problems of carbonate formation and CO2 crossover in neutral/alkaline electrolyzers. Alkali cations have been universally recognized as indispensable components for acidic CO2 R, while they cause the inevitable issue of salt precipitation. It is therefore desirable to realize alkali-cation-free CO2 R in pure acid. However, without alkali cations, stabilizing *CO2 intermediates by catalyst itself at the acidic interface poses as a challenge. Herein, we first demonstrate that a carbon nanotube-supported molecularly dispersed cobalt phthalocyanine (CoPc@CNT) catalyst provides the Co single-atom active site with energetically localized d states to strengthen the adsorbate-surface interactions, which stabilizes *CO2 intermediates at the acidic interface (pH=1). As a result, we realize CO2 conversion to CO in pure acid with a faradaic efficiency of 60 % at pH=2 in flow cell. Furthermore, CO2 is successfully converted in cation exchanged membrane-based electrode assembly with a faradaic efficiency of 73 %. For CoPc@CNT, acidic conditions also promote the intrinsic activity of CO2 R compared to alkaline conditions, since the potential-limiting step, *CO2 to *COOH, is pH-dependent. This work provides a new understanding for the stabilization of reaction intermediates and facilitates the designs of catalysts and devices for acidic CO2 R.

PEM Electrolysis in a Stirred‐Tank Bioreactor Enables Autotrophic Growth of Clostridium ragsdalei with CO2 and Electrons

AbstractAcetogenic bacteria produce CO2‐based chemicals in aqueous media by hydrogenotrophic conversion of CO2, but CO is the preferred carbon and electron source. Consequently, coupling CO2 electrolysis with bacterial fermentation within an integrated bio‐electrocatalytical system (BES) is promising, if CO2 reduction catalysts are available for the generation of CO in the complex biotic electrolyte. A standard stirred‐tank bioreactor was coupled to a zero‐gap PEM electrolysis cell for CO2 conversion, allowing voltage control and separation of the anode in one single cell. The cathodic CO2 reduction and the competing hydrogen evolution enabled in‐situ feeding of C. ragsdalei with CO and H2. Proof‐of‐concept was demonstrated in first batch processes with continuous CO2 gassing, as autotrophic growth and acetate formation was observed in the stirred BES in a voltage range of −2.4 to −3.0 V. The setup is suitable also for other bioelectrocatalytic reactions. Increased currents and lower overvoltages are however required. Atomically‐dispersed M−N−C catalysts show promise, if degradation throughout autoclaving can be omitted. The development of selective and autoclavable catalysts resistant to contamination and electrode design for the complex electrolyte will enable efficient bioelectrocatalytic power‐to‐X systems based on the introduced BES.

Machine learning assisted prediction of copper-based catalysts towards carbon dioxide electroreduction into carbon monoxide

Copper-based catalyst is very active for electroreduction of carbon dioxide (CO2) to carbon monoxide (CO). However, the Faraday efficiency of copper-based catalysts for CO production can be affected by many complex factors, such as catalyst elemental composition, morphology, supporting substrate, synthesis method, catalyst size, electrolyte concentration, and test potential with unknown correlations, hindering the efficient exploration of active copper-based CO2 reduction catalysts with high CO Faraday efficiency. In this study, a machine learning (ML) model is proposed towards rapid screening of copper-based catalysts with high CO selectivity using experimental database. The significance of different catalyst-related features on the CO Faraday efficiency was evaluated using feature importance and Spearman correlation coefficients. The ML model predicted that the dendrite Pd-doped copper oxides catalyst electroless deposited on copper mesh has the highest CO Faraday efficiency (92.8%). This ML study provides a useful guidance for the screening of copper-based catalysts towards the reduction of CO2 to CO.

Computational Design of Single-atom Modified Ti-MOFs for Photocatalytic CO2 Reduction to C1 Chemicals.

In this work, density functional theory (DFT) calculations were conducted to investigate a series of transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Ru, Rh, Pd, Ag, Hf, Ta, Os, Ir, and Pt) as single-atom components introduced into Ti-BPDC (BPDC=2,2'-bipyridine-5,5'-dicarboxylic acid) as catalysts (M/Ti-BPDC) for the photocatalytic reduction of CO2. The results show that Fe/Ti-BPDC is the most active candidate for CO2 reduction to HCOOH due to its small limiting potential (-0.40 V). Ag, Cr, Mn, Ru, Zr, Nb, Rh, and Cu modified Ti-BPDC are also active to HCOOH since their limiting potentials are moderate although the reaction mechanisms are different across these materials. Most of the studied catalysts show poor activity and selectivity to CO product because the stability of *COOH/*OCOH intermediates is significantly weaker than *OCHO/*HCOO species. The moderate binding strength of *CO on Pd/Ti-BPDC is responsible for its superior catalytic activity toward CH3OH generation. Electronic structural analysis was performed to uncover the origin of the activity trend for CO2 reduction to different products on M/Ti-BPDC. The calculation results indicate that the activity and selectivity of CO2 photoreduction can be effectively tuned by designing single-atom metal-based MOF catalysts.

Atomically Precise Silver Clusters Stabilized by Lacunary Polyoxometalates with Photocatalytic CO2 Reduction Activity.

The syntheses of atomically precise silver (Ag) clusters stabilized by multidentate lacunary polyoxometalate (POM) ligands have been emerging as a promising but challenging research direction, the combination of redox-active POM ligands and silver clusters will render them unexpected geometric structures and catalytic properties. Herein, we report the successful construction of two structurally-new lacunary POM-stabilized Ag clusters, TBA6 H14 Ag14 (DPPB)4 (CH3 CN)9 [Ag24 (Si2 W18 O66 )3 ] ⋅ 10CH3 CN ⋅ 9H2 O ({Ag24 (Si2 W18 O66 )3 }, TBA=tetra-n-butylammonium, DPPB=1,4-Bis(diphenylphosphino)butane) and TBA14 H6 Ag9 Na2 (H2 O)9 [Ag27 (Si2 W18 O66 )3 ] ⋅ 8CH3 CN ⋅ 10H2 O ({Ag27 (Si2 W18 O66 )3 }), using a facile one-pot solvothermal approach. Under otherwise identical synthetic conditions, the molecular structures of two POM-stabilized Ag clusters could be readily tuned by the addition of different organic ligands. In both compounds, the central trefoil-propeller-shaped {Ag24 }14+ and {Ag27 }17+ clusters bearing 10 delocalized valence electrons are stabilized by three C-shaped {Si2 W18 O66 } units. The femtosecond/nanosecond transient absorption spectroscopy revealed the rapid charge transfer between {Ag24 }14+ core and {Si2 W18 O66 } ligands. Both compounds have been pioneeringly investigated as catalysts for photocatalytic CO2 reduction to HCOOH with a high selectivity.

Atomically Precise Silver Clusters Stabilized by Lacunary Polyoxometalates with Photocatalytic CO2 Reduction Activity

AbstractThe syntheses of atomically precise silver (Ag) clusters stabilized by multidentate lacunary polyoxometalate (POM) ligands have been emerging as a promising but challenging research direction, the combination of redox‐active POM ligands and silver clusters will render them unexpected geometric structures and catalytic properties. Herein, we report the successful construction of two structurally‐new lacunary POM‐stabilized Ag clusters, TBA6H14Ag14(DPPB)4(CH3CN)9[Ag24(Si2W18O66)3] ⋅ 10CH3CN ⋅ 9H2O ({Ag24(Si2W18O66)3}, TBA=tetra‐n‐butylammonium, DPPB=1,4‐Bis(diphenylphosphino)butane) and TBA14H6Ag9Na2(H2O)9[Ag27(Si2W18O66)3] ⋅ 8CH3CN ⋅ 10H2O ({Ag27(Si2W18O66)3}), using a facile one‐pot solvothermal approach. Under otherwise identical synthetic conditions, the molecular structures of two POM‐stabilized Ag clusters could be readily tuned by the addition of different organic ligands. In both compounds, the central trefoil‐propeller‐shaped {Ag24}14+ and {Ag27}17+ clusters bearing 10 delocalized valence electrons are stabilized by three C‐shaped {Si2W18O66} units. The femtosecond/nanosecond transient absorption spectroscopy revealed the rapid charge transfer between {Ag24}14+ core and {Si2W18O66} ligands. Both compounds have been pioneeringly investigated as catalysts for photocatalytic CO2 reduction to HCOOH with a high selectivity.

Design of highly selective and stable CsPbI3 perovskite catalyst for photocatalytic reduction of CO2 to C1 products

Finding efficient photocatalytic carbon dioxide reduction catalysts is one of the core issues in addressing global climate change. Herein, the pristine CsPbI3 perovskite and doped CsPbI3 perovskite were evaluated in carbon dioxide reduction reaction (CO2RR) to C1 products by using density functional theory. Free energy testing and electronic structure analysis methods have shown that doped CsPbI3 exhibits more effective catalytic performance, higher selectivity, and stability than undoped CsPbI3. Additionally, it is discovered that CsPbI3 (100) and (110) crystal surfaces have varied product selectivity. The photo-catalytic effectiveness is increased by the narrower band gap of Bi and Sn doped CsPbI3, which broadens the absorption spectrum of visible light and makes electron transport easier. The calculation results indicate that Bi doped CsPbI3 (100) and CsPbI3 (110) crystal faces exhibit good selectivity towards CH4, with free energy barriers as low as 0.55 eV and 0.58 eV, respectively. Sn doped CsPbI3 (100) and CsPbI3 (110) crystal planes exhibit good selectivity for HCOOH and CH3OH, respectively. The results indicate that the Bi and Sn doped CsPbI3 perovskite catalyst can further improve the CO2 photocatalytic activity and high selectivity for C1 products, making it a suitable substrate material for high-performance CO2RR.

Boosting CO2 electrocatalytic reduction to ethylene via hydrogen-assisted C-C coupling on Cu2O catalysts modified with Pd nanoparticles

Direct electrochemical conversion of CO2 to C2H4 is a promising technology for high-value chemical synthesis. However, challenges arise from competing hydrogen evolution reactions (HER) and the formation of undesired C1 products. In this study, we successfully engineered palladium nanoparticles (Pd NPs) with hydrogen storage capabilities on the Cu2O interface. This strategic modification effectively controls hydrogen states at the interface, leading to simultaneous HER inhibition and a significant increase in C2H4 selectivity. Detailed insights into the reaction mechanism were obtained through in-situ infrared spectroscopy, in-situ X-ray diffraction (XRD) and controlled experiments, offering a molecular-level understanding of the reaction mechanism. The interface-modified Pd NPs provided stable *H intermediates during the reaction process, effectively suppressing HER. Furthermore, the direct bonding between Pd and Cu interfaces increases charge density at the copper sites. These copper sites, in conjunction with the Pd-H sites, activate *CO at the Pd-Cu interface, forming stable *CHO intermediates. This enhances the coupling of *CHO and *CO intermediates, resulting in a remarkable increase in the C2H4/H2 production rate from 0.4 to 2.0 after Pd NPs modification, with a high faradaic efficiency of up to 46%. Our work presents a promising approach for designing copper-based CO2 reduction catalysts with outstanding activity and selectivity.

Progress in design and preparation of multi-atom catalysts for photocatalytic CO2 reduction

Progress in design and preparation of multi-atom catalysts for photocatalytic CO2 reduction

Engineering of Ultra-Thin Layer of MIL-125(Ti) Nanosheet\Zn-Tetracarboxy-Phthalocyanine S-Scheme Heterojunction as Photocatalytic CO2 Reduction Catalyst.

Metal-organic frameworks (MOFs) with ultrathin 2D structure have attracted remarkable attention in photocatalytic application owing to the accessibility of abundant active sites on the surface. But high charge recombination results in poor photocatalytic activity. Herein, the synthesis of ultrathin MIL-125(Ti) nanosheets is reported with a thickness of 1.3nm through a simple chemical reaction route of precursor solution aging and subsequent solvothermal process for photocatalytic CO2 production. The maximal CO evolution rate achieves 200.8µmol g-1 h-1, which is prominently higher than that (78.6µmol g-1 h-1) of the bulk MIL-125(Ti) counterpart. Furthermore, the structurally stable Zn (II) tetracarboxy phthalocyanine (ZnTcPc) molecules assembly on ultrathin MIL-125(Ti) nanosheet (NS) to form MIL-125(Ti) NS\ZnTcPc S-scheme heterojunction through the strong interaction between the Ti3+ in MIL-125(Ti) and the COOH in ZnTcPc. The introduction of ZnTcPc greatly extends light absorption range and increases charge separation rate. The experimental and density functional theory calculation results validate that the MIL-125(Ti) NS\ZnTcPc S-scheme heterojunction can favor CO2 adsorption and effectively depress the formation energy of the intermediates, achieving a high CO evolution rate of 450.8µmol g-1 h-1. This work provides a strategy of engineering 2D MOF-based heterostructure systems for photocatalytic application.

Screening of Transition Metal Supported on Black Phosphorus as Electrocatalysts for CO2 Reduction.

The electrocatalytic CO2 reduction (CO2RR) is an effective and economical strategy to eliminate CO2 through conversion into value-added chemicals and fuels. However, exploring and screening suitable 2D material-based single-atom catalysts (SACs) for CO2 reduction are still a great challenge. In this study, 27 (3d, 4d, and 5d, except Tc and Hg) transition metal (TM) atom-doped black phosphorus (TM@BP) electrocatalysts were systematically investigated for CO2RR by density functional theory calculations. According to the stability of SACs and their effectiveness in activating the CO2 molecule, three promising catalysts, Zr@BP, Nb@BP, and Ru@BP, were successfully screened out, exhibiting outstanding catalytic activity for the production of carbon monoxide (CO), methyl alcohol (CH3OH), and methane (CH4) with limiting potentials of -0.79, -0.49, and -0.60 V, respectively. A catalytic relationship between the d-band centers of SACs and the limiting potential of CO2RR was used to estimate the catalytic activity of catalysts. Furthermore, Nb@BP has high selectivity for CO2RR to CH3OH compared to H2 formation, while the hydrogen evolution reaction significantly impacts the synthesis of CO and CH4 on Zr@BP and Ru@BP. Nitrogen atom doping in BP is beneficial for enhancing the selectivity of CO2RR, but it is detrimental to the activity of CO2RR. This study offers theoretical guidance for synthesizing highly efficient CO2RR electrocatalysts and further enhances structural modulation methods for layered 2D materials.

Catalytic conversion of carbon dioxide (CO2) using coal-based nano-carbon materials.

Carbon dioxide (CO2) is a prominent greenhouse gas and a widely available carbon resource. The chemical conversion of CO2 into high-value chemicals and fuels is a significant approach for mitigating carbon emissions and attaining carbon neutrality. However, enhancing CO2 adsorption and conversion rates remains a primary challenge in CO2 recycling. The development of high-performance catalysts is pivotal for the catalytic conversion of CO2. In this context, coal-based carbon materials, characterized by their extensive specific surface area and adaptable chemical composition, can offer more reactive active sites and have robust CO2 adsorption capabilities. They can function as either standalone catalysts or as components of composite catalysts, making them promising materials for CO2 reduction. The use of affordable and abundant coal as a precursor for carbon materials represents a crucial avenue for achieving clean and efficient coal utilization. This paper reviews the progress of research on coal-based carbon materials and examines their advantages and challenges as catalysts for CO2 reduction.

Polymerized ionic liquid Co-catalysts driving photocatalytic CO2 transformation.

Photocatalytic production of CO from CO2 has the potential for safe and atom-economic production of feedstock chemicals via in situ carbonylation chemistry. We developed novel ionic liquid-based polymeric materials through radical copolymerisation of 1-butyl-3-vinylimidazolium chloride and photocatalytically active Re- and Ru-complexes that serve as the CO2 reduction catalyst and photosensitiser, respectively. The crosslinked polymeric framework allows for the facile immobilisation of molecular organometallic complexes for use as heterogenised catalysts; moreover, the involved imidazolium core units co-catalyze the reduction of CO2 via covalent interaction. The ratio of sensitiser and catalyst was analysed by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) and set in relation to results from photocatalytic experiments. Ultimately, the heterogenous polymeric framework showed high selectivity for CO formation on photocatalytic CO2 reduction with improved stability to the corresponding homogenous system.

Self-assembled infinite silver cluster with atomic precision as a scalable catalyst for CO2-electroreduction under industry-relevant reaction rates

Scalable infinite silver acetylide cluster as a CO2 reduction catalyst with high selectivity for CO at industry-relevant rates.