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DFT calculations of electron density. PDOSs for spin-up channel of: (a) the Mo atom at the edge and Mo atom within the lattice; (b) s, p, and d orbital of Mo-edge atom. (c) PDOS of d band of Mo-edge atom, Ag atom from bulk and Ag-slab of 8.32-Å thickness. Electron density on Mo-edge atom is significantly (~11 times) higher than the electron density on Ag atom.
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Electrochemical reduction of carbon dioxide has been recognized as an efficient way to convert carbon dioxide to energy-rich products. Noble metals (for example, gold and silver) have been demonstrated to reduce carbon dioxide at moderate rates and low overpotentials. Nevertheless, the development of inexpensive systems with an efficient carbon dio...
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... 2 also exhibits a significantly high CO 2 reduction current density (65 mA cm À 2 at À 0.764 V), where CO 2 is selectively converted to CO (FEB98%). However, at the same potential ( À 0.764 V), the bulk Ag catalyst shows a considerably lower current density (3 mA cm À 2 ) (Fig. 2a) but for the H 2 formation ( Supplementary Fig. 4a). Ag NPs (average diameter of 40 nm) show only a current density of 10 mA cm À 2 with 65% selectivity for the CO formation under the same experimental conditions ( Fig. 2a and Supplementary Fig. 4b). ...
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... at the same potential ( À 0.764 V), the bulk Ag catalyst shows a considerably lower current density (3 mA cm À 2 ) (Fig. 2a) but for the H 2 formation ( Supplementary Fig. 4a). Ag NPs (average diameter of 40 nm) show only a current density of 10 mA cm À 2 with 65% selectivity for the CO formation under the same experimental conditions ( Fig. 2a and Supplementary Fig. 4b). In addition, the CO 2 reduction current density for MoS 2 is also significantly higher ARTICLE than the maximum current density (B8.0 mA cm À 2 ) achieved when Ag NPs were used in the dynamic electrochemical flow cell using a similar electrolyte solution 13 . ...
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... 35 . We found that the electronic structure of MoS 2 ribbons (Supplementary Note 2) is near E f formed by edge bands of only one-spin polarization, originating from the Mo and S atoms exposed at both MoS 2 edges. In the vicinity of E f, the spin-polarized PDOS for these Mo atoms is approximately twice larger than that of the bulk Mo atoms (Fig. 4a). Since the bulk Mo atoms, sandwiched between two S layers, are not directly exposed to the electrolyte, the MoS 2 catalytic activity should be primarily related to the edge states formed by Mo-edge atoms (Supplementary Fig. 7). The S atoms possess less reactive p orbitals ( Supplementary Fig. 8), and they are not present at the ...
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... we resolved the PDOS of the Mo-edge atoms into s-, p- and d-orbital electron contributions (Fig. 4b). The obtained data indicate that near E f , the PDOS is dominated by d-orbital (Mo) electron states, which are known to actively participate in catalysed reactions 35 . The Mo d electrons form metallic edge states 37 (Supplementary Note 2), which can freely supply electrons to the reactants attached at the edges. To assess how the ...
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... all these d-electron states near E f can be accessed in the reaction, supporting the large observed MoS 2 activity. Finally, we compared our d-orbital PDOS in Mo-edge atoms with that in Ag atoms in two structures: a bulk Ag and a two-dimensional slab Ag (both fcc lattice with a lattice constant of 4.09 Å) of a 8.32-Å thickness (after relaxation) (Fig. 4c). We found that the d-band centre for Mo-edge atoms is closer to the Fermi energy level than that in both Ag structures. This can partly explain the high catalytic activity of MoS 2 , since the higher the d-band centre is, the more reactive the metal is due to a lower transition state energy 35 . Moreover, the PDOS of Mo-edge atoms near ...
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... of CO and H 2 was examined separately. Ultra high-purity helium (purchased through AirGas) was used as a carrier gas for CO detection, whereas ultra high-purity nitrogen (AirGas) was utilized for H 2 detection (Supplementary Note 4). Initially, GC system was calibrated for CO and H 2 . ...
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... Ionic liquids are another potential electrolyte for enhancing the electrochemical effect reduction of CO 2 . Previous studies have shown that employing Ionic liquid electrolytes with various electrodes can lead to CO 2 reduction [245][246][247]. It is hypothesized that forming a complex via ion pairing between the Ionic liquid cation and the CO 2 radical anion could decrease the activation overpotential [245]. ...
... Each layer of TMDs consists of three atomic layers, which have shown outstanding performance in electrocatalysis. [38] For example, Asadi et al. [39] reported that MoS 2 shows remarkably high current response (65 mA cm À 2 with an overpotential of 654 mV) and high selectivity (FE of 98 %) for CO production because their molybdenum-terminated edges of MoS 2 possess metallic character and high d-electron density ( Figure 5). Furthermore, many factors, such as edge site, layer size, electronic structure, and crystal phase, could affect the electrocatalytic performance of TMDs in the application of eCO 2 RR. ...
The electrochemical carbon dioxide reduction reaction (eCO2RR) can achieve carbon recycling through renewable electrical energy. Before releasing the full potential of eCO2RR, the electrocatalysts still need improvement in terms of catalytic activity, selectivity, and durability. Two‐dimensional (2D) crystalline materials show a high aspect ratio with well‐defined crystal structures, which are promising electrocatalysts for eCO2RR. In this review, we briefly discuss the typical 2D electrocatalysts for eCO2RR. Subsequently, we provide a summary of the different strategies to improve the catalytic performance of 2D crystalline electrocatalysts for creating and modulating active sites. Finally, we end this review with the current challenges and future opportunities of 2D crystalline materials in the eCO2RR.
... Also, the high CO 2 reduction current density is mainly attributed to the low transition state energy of the undercoordinated Mo atoms at the material edge and the high d electron density ( Figure 11C). 100 These marginal Mo atoms enable efficient activation and reduction of CO 2 molecules. Similarly, the research team also reported on some 2D nanoflakes, which reduce CO 2 into carbon monoxide (CO) in ionic liquids. ...
Molybdenum disulfide (MoS 2 ) has garnered significant attention in the field of catalysis due to the high density of active sites in its unique two‐dimensional (2D) structure, which could be developed into numerous high‐performance catalysts. The synthesis of ultra‐small MoS 2 particles (<10 nm) is highly desired in various experimental studies. The ultra‐small structure could often lead to a distinct S–Mo coordination state and nonstoichiometric composition in MoS x , minimizing in‐plane active sites of the 2D structure and making it probable to regulate the atomic and electronic structure of its intrinsic active sites on a large extent, especially in MoS x clusters. This article summarizes the recent progress of catalysis over ultra‐small undoped MoS 2 particles for renewable fuel production. Through a systematic review of their synthesis, structural, and spectral characteristics, as well as the relationship between their catalytic performance and inherent defects, we aim to provide insights into catalysis over this matrix that may potentially enable advancement in the development of high‐performance MoS 2 ‐based catalysts for sustainable energy generation in the future.
... Therefore, the quest for optimal catalysts has emerged as a focal point in this field, representing a critical step toward establishing a sustainable carbon-centric economy. However, several formidable challenges persist in the landscape of CO 2 electrochemical reduction [5,6]. These challenges encompass catalyst stability, cost-effectiveness, scalability, intricate reaction mechanisms, and more. ...
This investigation provides a comprehensive exploration into the intricate interplay between topological surface states and catalytic performance in two-dimensional (2D) materials, with specific emphasis on monolayer Cu2Se. Leveraging the unique characteristics of nodal loop semimetals (NLSMs), we delve into the precise influence of topological surface state on catalytic activity, particularly in the domain of CO2 electrochemical reduction. Our findings illuminate the central role played by these topological surface states, arising from the underlying NLSM framework, in sculpting catalytic efficiency. The length of these surface states emerges as a critical determinant of surface density of states (DOSs), a fundamental factor governing catalytic behavior. Extension of these surface states correlates with heightened surface DOSs, yielding lower Gibbs free energies and consequently enhancing catalytic performance, particularly in the electrochemical reduction of CO2. Moreover, we underscore the profound importance of preserving symmetries that protect the nodal loop. The disruption of these symmetries is found to result in a significant degradation of catalytic efficacy, underscoring the paramount significance of topological features in facilitating catalytic processes. Therefore, this study not only elucidates the fundamental role of topological surface states in dictating the catalytic performance of topological 2D materials but also paves the way for harnessing these unique attributes to drive sustainable and highly efficient catalysis across a diverse spectrum of chemical processes.
... [14][15] Among them, the electrocatalytic CO 2 RR technology is one of the most attractive strategies because it can be operated under mild conditions. [16][17] such as ambient temperature and atmospheric pressure, and has several advantages, such as energy versatility, product versatility, environmental friendliness, and sustainability. [18][19] The electrocatalytic CO 2 RR technology utilizes an electric current to break down carbon dioxide into oxygen and carbonbased compounds, [20][21] with common products including carbon monoxide, methanol, [22][23] formic acid, [24] and ethanol. ...
In order to address the greenhouse effect and achieve the artificial carbon cycle, the electrocatalytic reduction reactions offer an effective approach for converting carbon dioxide (CO2) into valuable chemicals. In addition to the rational design of catalyst structure to improve the high selective conversion of CO2, exploring the influence of environmental conditions on the reaction path and product types is one of the keys to realizing the high selective conversion of CO2. In this review, we illustrate the important influence of changes in environmental conditions on the effectiveness of electrocatalytic carbon dioxide reduction reaction (CO2RR) technology from the design of the reactor, the selection of the electrolyte, and the setting of the reaction conditions (pressure, temperature, etc.). Through in‐depth understanding and optimization of these factors, the efficiency and selectivity of the CO2RR can be further improved to promote the development of CO2 conversion technology.
... Various materials, including metalbased oxides, alloys and chalcogenides have been successfully employed for catalyzing the ECR. [16][17][18] Among them, metal porphyrins and phthalocyanines have emerged as promising catalysts for the CO production. [19,20] This class of materials features high catalytic activity and tenability, relying on earthabundant metals (e. g., Co, Fe). ...
The development of low‐cost and efficient electrolyzer components is crucial for practical electrochemical carbon dioxide reduction (ECR). In this study, facile non‐woven cellulose‐based porous transport layers (PTLs) were developed for high current density CO2‐to‐CO conversion. By depositing a cobalt phthalocyanine (CoPc) catalyst‐layer over the PTLs, we fabricated ECR‐functioning gas‐diffusion‐electrodes (GDEs) for both flow‐cell and zero‐gap electrolyzers. Under optimal conditions, the Faradaic efficiency of CO (FECO) reached 92 % at a high current density of 200 mA cm⁻². Furthering the architecture of the GDEs, CoPc was incorporated into the initial PTL slurry, forming ECR‐active PTLs without the need for an additional catalyst‐layer. The new GDE‐architecture favored the CoPc‐distribution by enhancing the contact and interactions with the carbon substrate and demonstrated a stable electrolysis process for over 50 h in a zero‐gap cell at 200 mA cm⁻² with a FECO of 80 %.
... Some present works on catalysis involve the generation of green hydrogen, which consists of splitting water molecules [1]. The atmospheric nitrogen [2] and carbon dioxide [3] could help generate useful essential chemical products with less energy consumption. Moreover, carbon dioxide reduction itself is beneficial to the environment. ...
... Initially, the electrochemical reduction of CO 2 has been carried out using noble metals like gold and silver. Later, Asadi et al., in 2014 first showed that CO 2 conversion is possible with the help of MoS 2 [3]. A work by Xie et al. showed the mechanism of reduction of CO 2 to CO on the monolayer of MoS 2 . ...
... The [EMIM-CO 2 ] + complex physically adsorbed at the negatively charged MoS 2 cathode, resulting in a close contact of CO 2 molecules with the MoS 2 surface. [82] However, the application of ionic liquids may significantly increase the operating cost of the CO 2 electrolyzer because of the high cost of the ionic liquids. To reduce the usage, ionic liquids can be utilized to modify the catalysts instead of being added into the electrolyte. ...
Electrochemical carbon dioxide reduction (CO2R) is a promising pathway for converting greenhouse gasses into valuable fuels and chemicals using intermittent renewable energy. Enormous efforts have been invested in developing and designing CO2R electrocatalysts suitable for industrial applications at accelerated reaction rates. The microenvironment, specifically the local CO2 concentration (local [CO2]) as well as the water and ion transport at the CO2–electrolyte–catalyst interface, also significantly impacts the current density, Faradaic efficiency (FE), and operation stability. In nature, hydrophobic surfaces of aquatic arachnids trap appreciable amounts of gases due to the “plastron effect”, which could inspire the reliable design of CO2R catalysts and devices to enrich gaseous CO2. In this review, starting from the wettability modulation, we summarize CO2 enrichment strategies to enhance CO2R. To begin, superwettability systems in nature and their inspiration for concentrating CO2 in CO2R are described and discussed. Moreover, other CO2 enrichment strategies, compatible with the hydrophobicity modulation, are explored from the perspectives of catalysts, electrolytes, and electrolyzers, respectively. Finally, a perspective on the future development of CO2 enrichment strategies is provided. We envision that this review could provide new guidance for further developments of CO2R toward practical applications.
... 14 Moreover, MoS 2 with molybdenum-terminated edges has shown good CO 2 reduction performance with low overpotential and high current density. 15 MoS 2 -CuO based nanocomposite (NC) heterostructures have been successfully synthesized by many authors, and these NCs have shown an exceptionally wide range of applications such as asymmetric supercapacitors, enhanced photocatalysis, pollutant degradation, photothermal therapy, and nonenzymatic glucose sensors. 16−20 However, synthesis methods used in those studies do not select for any specific morphology and proper surface termination of CuO nanostructures, and most of them are nanoparticles or nanoflowers with {111} surface termination, which is not suitable for CO 2 RR, and the staggered type-II band alignment formed at the heterostructures shows low conductivity, decreasing electrocatalytic efficiency. ...
A novel CuO-MoS2 based heterostructure catalyst model system is proposed where a CuO nanosheet with exposed {001} facet with proper termination is the active surface for the catalysis and a MoS 2 nanosheet is the supporting layer. Density functional theory (DFT) calculations were performed to validate the model. The MoS 2 bilayer forms a stable heterostructure with {001} faceted CuO with different terminations exposing oxygen and copper atoms (active sites) on the surface. The heterostructure active sites with a low oxidation state of the copper atoms and subsurface oxygen atoms provide a suitable chemical environment for the selective production of multicarbon products from CO2 electrocatalytic reduction. Furthermore, our heterostructure model exhibits good electrical conductivity, efficient electron transport to active surface sites, and less interfacial resistance compared to similar heterostructure systems. Additionally, we propose a photoenhanced electrocatalysis mechanism due to the photoactive nature of MoS2. We suggest that the photogenerated carrier separation occurs because of the interface-induced dipole. Moreover, we utilized a machine learning model trained on a 2D DFT materials database to predict selected properties and compared them with the DFT results. Overall, our study provides insights into the structure− property relationship of a MoS2 supported 2D CuO nanosheet based bifunctional catalyst and highlights the advantages of heterostructure formation with selective morphology and properly terminated surface in tuning the catalytic performance of nanocomposite materials.
... (iv) Modified metals: Researchers experienced the electrode particles size involved in ERC have great influence on Faraday efficiency, energy efficiency and product selectivity [44,115,116,[123][124][125][126][127][128][129]. Advancements in nanoparticle synthesis techniques have enabled the study of the impact of controlled surface area and surface morphology on enhanced reaction kinetics. ...
... Recently, ionic liquids have attracted great attention of researchers as non-aqueous electrolyte in ERC experiments as it capable of forming a Lewis-base adduct with CO2 and exhibiting activity in the CO2 reduction process [42,43,125,126,[183][184][185][186][187][188]. Rosen et al. [187] reported an electrocatalytic system that relies on an ionic liquid electrolyte to convert CO2 to CO at overpotentials less than 0.2 volt. ...
Various methods have been suggested to address the problem of elevated levels of carbon dioxide (CO2) in the atmosphere. A potential technique among these strategies is the electrochemical reduction of CO2 (ERC), which can simultaneously solve issues like CO2-induced global warming and enable sustainable energy storage. The ERC procedure takes place within an electrochemical cell at the interface between an ionic conductor (the electrolyte) and an electron conductor (the cathode). In this process, the anode facilitates the oxidation of water, while the cathode enables CO2 reduction. However, a significant challenge in the ERC process lies in selecting an appropriate catalyst for the cathode material. In addition to explore the new transition metals, researchers have also investigated metal complex catalysts and nanostructures to enhance catalyst activity and product selectivity. Non-aqueous electrolytes have been employed to avoid the hydrogen evolution reaction. Ionic liquids have been proposed as a solution to address the challenge of low CO2 solubility in the reaction medium, offering significant potential for enhancing conversion rates to resolve the limitations faced by aqueous and non-aqueous systems solid polymer electrolytes are being considered. The cell configuration has been continuously improved to improve the mass transfer effects and to better separate the reaction products. This review paper provides a preface to the ERC process and an inclusive review of several decades of research work on ERC process by analyzing the adopted various and novel cathode materials, electrolytes and cell configuration.
