Alkali Metal Promoters Research Articles

Enhanced catalytic performance for gas phase epoxidation of propylene with H2 and O2 by multiple pretreated Au/TS-1 catalysts

Direct epoxidation of propylene (C3H6) with hydrogen (H2) and oxygen (O2) over Au/TS-1 catalyst was promising way for the synthesis of propylene oxide (PO). However, high selectivity of PO (>95 %) and conversion of C3H6 (>5 %) cannot be achieved at the same time. The industrialization process was severely restricted. In this paper, Au/TS-1 catalysts were synthesized by deposition precipitation method with alkali metal promoter. And alkaline gases and silane coupling post-treatment were performed to promote the catalytic activity. The prepared samples exhibited a much better C3H6 conversion (6.5 %) and PO selectivity (95.1 %) compared with general catalyst using normal synthetic technology. Cs2CO3 was beneficial to increasing Au nanoparticles uptake efficiency. Both NH3 and triethoxyvinylsilane post-treatment were good for smaller and more uniform loading of Au nanoparticles. The decreasing in surface hydroxyl density effectively alleviated the occurrence of PO ring opening isomerization. The increased hydrophobicity of TS-1 surface was conducive to the rapid desorption of generated PO and significantly increased PO selectivity. Multiple pretreatment was also favorable for extending the lifetime of Au/TS-1 catalyst.

Structural evolution of cobalt for the production of long-chain paraffins by CO2 hydrogenation

A new role of alkali metals in the direct hydrogenation of CO2 to C5+ species over Co catalysts was proposed. During the CO2 hydrogenation, Na-promotion encouraged a new structural evolution (i.e., a thin oxygen vacancy (Ov)-rich Co3O4/Co2C shell and a Co0 core). This facilitated the migration of CHxO and CO species produced at the shell to the adjacent Co2C shell and Co0 core, where they undergo further chain growth. In contrast, Li- and K-promotion resulted in the generation of a thick and Ov-poor Co3O4 shell without Co2C, while in the absence of alkali metal promotion, Co0 was exposed as the outmost surface; in both the cases, methanation dominated. The ability of Na-promotion to remove –OH* from the Co surface helped maintain the thickness and valance state of the Co oxide shell. Thus, the Na-promotion developed the chain growth and CO producing core–shell structure, rather than any electronic promotional effects.

Supremacy of in-situ doping over surface loading technique for the preparation of alkali metal-promoted tellurates as efficient reusable catalysts to approach hydroxylation and dehalogenation of aryl halides

The novel alkali metal doped transition metal tellurate catalysts are prepared by two different methods, namely the in-situ doping method (alkali metal is added to the hydroxides of copper and tellurium and then calcinated) and surface loading method (alkali metal is added to the as-prepared metal tellurate and then calcined second time). In this study, the supremacy of in-situ doping over surface loading of alkali metal promoters (AM: Na, K, Rb, or Cs) to the metal tellurate for hydroxylation of aryl halides and dehalogenation of aryl halides reactions are investigated. Besides, the catalytic activity depends on the AM used for doping; the decreasing order of activity is K-Cu3TeO6 > Na-Cu3TeO6 > Rb-Cu3TeO6 > Cs-Cu3TeO6 and the occupancy of AM is in the sequence of Cs+ < Rb+ < K+ < Na+. The presence of the potassium on the copper tellurate is confirmed by XPS and flame photometry even after 6 cycles.

Effect of Na+ migration and the component proximity on direct conversion of aromatics into aromatics over Fe-based zeolite bifunctional catalysts

Direct conversion of syngas into aromatics (STA) via Fischer-Tropsch (F-T) synthesis, using Fe-based zeolite bifunctional catalysts, has recently become a topic of great interest. The catalytic performance of the Fe-based zeolite bifunctional catalyst is influenced by the component proximity in the STA reaction, in addition to their physicochemical properties. However, the mechanism by which the component proximity affects the STA performance is still unclear. Herein, we investigate the effect of Na+ migration and the component proximity on the F-T reactivity, the aromatic distribution, and catalyst stability in a Fe-based ZSM-5 catalyst system. The correlation between the proximity of two components, the migration of alkali-metal promoters, the evolution of the Fe-based active phase, and the coke on the zeolite is analyzed using XRD, XPS, FT-IR, TG, Mössbauer spectroscopy techniques. The findings indicate that when the components are closer to each other, it encourages the formation of iron carbides and inhibits the coke deposition on the zeolite. However, the migration of alkali metals and the acidic environment of zeolite can decrease the catalyst’s stability and F-T reactivity. Moreover, by improving the hydrophobic nature of the zeolite, we can prevent the transfer of alkali-metal promoters from the Fe-based component to zeolite. This enhances the stability of Fe-based ZSM-5 catalysts in the STA reaction, suggesting a new approach to improve their STA performance.

A Brief Review of Recent Theoretical Advances in Fe-Based Catalysts for CO2 Hydrogenation.

Catalytic hydrogenation presents a promising approach for converting CO2 into valuable chemicals and fuels, crucial for climate change mitigation. Iron-based catalysts have emerged as key contributors, particularly in driving the reverse water-gas shift and Fischer-Tropsch synthesis reactions. Recent research has focused on enhancing the efficiency and selectivity of these catalysts by incorporating alkali metal promoters or transition metal dopants, enabling precise adjustments to their composition and properties. This review synthesizes recent theoretical advancements in CO2 hydrogenation with iron-based catalysts, employing density functional theory and microkinetic modeling. By elucidating the underlying mechanisms involving metallic iron, iron oxides, and iron carbides, we address current challenges and provide insights for future sustainable CO2 hydrogenation developments.

Theoretical insight into the promotion effect of potassium additive on the water-gas shift reaction over low-coordinated Au catalysts.

How to elucidate the effect of alkali metal promoters on gold-catalyzed water-gas shift reaction intrinsically remains a challenging, because that the complex synergy effects such as strong metal-support interactions, interfacial effects, and charge transfer of supported metal catalysts makes people difficulty in the understanding the alkali promotion phenomenon in nature. Herein, we report a systematically study of whole water-gas shift reaction mechanism on pure and the K-modified defected-Au(211) (i.e., by removing one surface Au atom from perfect Au(211) and make one model with the Au-Au coordination number is six) by using the microkinetic modeling based on first principles. Our results indicate that the presence of K can increase the adsorption ability of oxygen-containing species via the attractive coulomb interaction, has no significant effect on the adsorption of H species, but inhibits the adsorption of CO due to the steric effect. K promoter stabilizes the water adsorption by ~0.3 eV, which results in one order increasing of whole reaction rate. Interestingly, the strong promotion effect of the K can be assigned to the significant direct space interaction between K and the adsorbate H2O* through the inducted electric field, which can be further confirmed by the posed negative electric field on the unpromoted D-Au(211). Microkinetic modeling results revealed that the carboxyl mechanism is the most likely to occur, redox mechanism is the next one, and the formate mechanism is the least likely to occur. For different kinds of alkali metal additives, the adsorption strength of water molecules gradually weakens from Li to Cs, but Na shows the best promoter behavior at the low temperature. By considering the effect of K contents on the reactivity of water-gas shift reaction, we found that the K with the medium coverage (~0.2~0.3 ML) has the strongest promoting effect. It is expected that the conclusion of this work can be extended to other WGSR catalytic systems like Cu(or Pt). All calculations were performed by using the plane-wave based periodic method implemented in Vienna ab initio simulation package (VASP, version 5.4.4), where the ionic cores are described by the projector augmented wave (PAW) method. The exchange and correlation energies were computed using the Perdew, Burke and Ernzerhof functional with the vdw correction (PBE-D3). The transition states (TSs) were searched using the climbing image nudged elastic band (CI-NEB) method. Some electronic structure properties like work function was predicated by the DS-PAW software. Microkinetic simulation was carried out using MKMCXX software.

Alkali-promoted copper catalyst catalyze low-temperature water-gas shift reaction

The addition of alkali metal promoter is significant to improve the performance of copper catalyst in water–gas shift reaction (WGSR), but the previous theoretical work mainly focuses on the single crystal metal model like Cu(111), rather than the real supported copper clusters. In this paper, Cu4/TiO2(sub-nanometer), Cun/TiO2 (copper nanorod) were chosen to explore the effect of K on WGSR where K is located on TiO2 support, Cu/TiO2 interface, and copper clusters surface. Density functional theory calculation results show that only when K is on Cun/TiO2 and Cu(111) surfaces, can K promote water–gas shift reaction. Microkinetic modeling analysis shows that K mainly promotes the water–gas shift reaction by promoting the decomposition of H2O, and has little influence on the C-O bond formation like carboxyl and CO2. Combined with energetic, electronic and geometric analysis, on the surfaces of Cun/TiO2 and Cu(111), K mainly enhances the adsorption strength of H2O and reduces the barrier of H2O dissociation through direct bonding with oxygenate species, thereby improving the performance of WGSR. The copper clusters with sub-nanometer size cannot reveal the promotion effect of K, and the microkinetic modeling results of Cu(111) surface do not conform to the real situation, but the copper nanorod model can appropriately reflect the promotion effect of K. The structure unit of the active center is [TiO2−Cu−K]. The promotion of other alkali metals was explored, and the microkinetic modeling results show that the order of alkali metal promotion is as follows: Li < Na < K < Rb < Cs. The electronic structure analysis shows that the smaller the electronegativity of alkali metal, the lower the surface work function, the higher the surface dipole moment, and the stronger the promoting effect of alkali metal. This work not only reveals the origin of the K effect on WGSR, but also provides the accurate placement of K promoter.

K–ZrO2 Interfaces Boost CO2 Hydrogenation to Higher Alcohols

Alkali metal promoters are widely used to modify active metal sites/interfaces of heterogeneous catalysts for numerous industrial processes. However, the interplay between an alkali metal and support, a crucial catalytic parameter, has been scarcely investigated in controlling the activation behaviors of intermediates and improving catalysis. Herein, we report that K–ZrO2 interfaces can boost the production of higher alcohols (HA) from CO2 hydrogenation over an amorphous ZrO2-supported K–Cu–Fe catalyst (KFeCu/a-ZrO2). In situ spectroscopy and chemisorption demonstrate that the strong interactions between K and ZrO2 induce the formation of surface Zrδ+ sites/oxygen vacancies at K–ZrO2 interfaces, thus providing plenty of nondissociative CO activation sites. The improved molecular CO adsorption capacity at the K–ZrO2 interfaces expedites the CO insertion reaction (*CHx + *CO → *CHx-CO) at Cu–Fe5C2 interfaces, thereby driving the HA synthesis reaction with nearly 4.6 times higher activity of HA in comparison to the KFeCu/SiO2 catalyst. At the optimal conditions of 320 °C, 4 MPa, and 12 L gcat–1 h–1, the KFeCu/a-ZrO2 catalyst shows the HA space time yield of 125.0 mg gcat–1 h–1, ranking the top level among the reported single-component catalysts in the literature. Most importantly, this work provides an in-depth insight into alkali promoter–support interactions for promoting catalytic performance.

The Promotional Effect of Na on Ru for pH-Universal Hydrogen Evolution Reactions

Alkali metals, as ideal electron donors, can effectively regulate the valence state distribution of the host metals. Nevertheless, no studies have reported the application of alkali metal promoters in the hydrogen evolution reaction (HER). Here, we designed an efficient and wide pH-universal hydrogen evolution catalyst that utilizes alkali metal to control the valence, size, and dispersion of Ru NPs. The experimental results reveal that the alkali metal additives contribute to the dispersion and stabilization of metallic Ru. More importantly, the interaction between Na and Ru regulates the distribution of Ru valence states and helps to form more active components of Ru0. Additionally, NaCl functioned as an in situ template to assist the construction of a porous carbon skeleton promotes mass transfer and exposes more active sites, further promoting the synergistic effect of Ru and Na. As a result, the optimal Ru0.3/C−800 delivers high efficiency for HER with an overpotential as low as 29 mV in 1.0 M KOH and 83 mV in 0.5 M H2SO4 under 10 mA cm−2. Particularly, the catalytic performance of Ru0.3/C−800 even outbalanced that of commercial Pt/C in an alkaline medium. This rational construction strategy opens up new avenues for obtaining superior pH-universal electrocatalysts.

Identifying the Performance Descriptor in Direct Syngas Conversion to Long-Chain α-Olefins over Ruthenium-Based Catalysts Promoted by Alkali Metals

Fischer-Tropsch synthesis (FTS) provides a nonpetroleum route for the production of value-added α-olefins from syngas. However, regulating the product distribution to promote the formation of long-chain α-olefins while maintaining low selectivity to C1 byproducts (CO2 and CH4) remains a great challenge. Herein, a series of alkali metal-promoted Ru/SiO2 catalysts were synthesized to investigate the effect of alkali metals and identify the performance descriptor for syngas to α-olefins. X-ray absorption and photoelectron spectroscopy as well as CO diffuse reflectance infrared Fourier transformation spectra revealed that Ru’s electronic structure can be tuned by the addition of alkali metal promoters. The Allen scale electronegativity deviation between the metallic Ru and the alkali metal promoter, which was identified as a performance descriptor, was correlated with the initial turnover frequency (TOF) and olefins distribution, as well as the chain growth probability. In addition, the fraction of olefin products was successfully adjusted from lower olefins (50.3%) to long-chain α-olefins (85.8%) by controlling the kinds of alkali metal promoters. Evidences from X-ray absorption spectroscopy and chemisorption characterizations revealed that the controllable Ru electron density could enhance CO adsorption and hinder the reactivity of chemisorbed H species, thus benefiting the α-olefin production. These results offer a comprehensive view of the electronic effect for regulating product selectivity during the Fischer-Tropsch reaction process.

Effect of alkali metal promoters on catalytic performance of Co-based catalysts in selective hydrogenation of aniline to cyclohexylamine

Abstract In this study, a series of Co-based catalysts with alkali metal carbonate promoters were prepared to investigate the interrelation between promotion effect of these carbonates and catalytic performance for aniline hydrogenation to cyclohexylamine in vapour phase. The chemical promoters Li2CO3 and Na2CO3 leading to decrease in catalytic activity of cobalt catalysts for aniline hydrogenation. Catalysts with K2CO3 and Cs2CO3 loadings have practically no catalytic activity for hydrogenation of aniline. Results of TPD of aniline proved that presence of alkali metals carbonates restricts the adsorption of aniline on the surface of cobalt catalysts. Further, it was found that the addition of Na2CO3 greatly enhances the catalytic selectivity towards the cyclohexylamine and inhibits the consecutive reactions of cyclohexylamine leading to formation of by-products such as dicyclohexylamine and N-phenylcyclohexylamine.

Potassium as the best alkali metal promoter in boosting the hydrogenation activity of Ru/MgO for aromatic LOHC molecules by facilitated heterolytic H2 adsorption

Alkali metals (AM) are frequently used as promoters in a number of reactions. In aromatic hydrogenation over Ru/MgO, their basicity may promote heterolytic H2 adsorption, thereby boosting reaction kinetics. Herein, Ru/AM/MgO catalysts (AM: Na, K, and Cs) with different AM/Ru molar ratios are prepared and evaluated in the hydrogenation of toluene and benzyltoluene. The activity exhibits a volcano-type relationship with the AM/Ru molar ratio, where the optimal AM content decreases in the order Na+ > K+ > Cs+ and the AM showing the best activity is in the sequence Cs+ < Na+ < K+. These results originate from the heterolytic H2 adsorption induced by charge transfer from AM to proximate Ru atoms at the Ru–MgO interface. The degree of charge transfer depends on the AM’s ionic radius and electronegativity affecting surface mobility and charge donation ability. Consequently, K+ is the best AM promoter in Ru/MgO-catalyzed aromatic hydrogenation.

Effect of Na promoter and reducing atmosphere on phase evolution of Fe-based catalyst and its CO2 hydrogenation performance

Although alkali metal promoters have a considerable effect on the product distribution of CO2 hydrogenation over Fe-based catalysts, the mechanism of the active phase transformation is uncertain. The effects of Na modification and pretreatment atmosphere on phase evolution of Fe2O3 sample and the synergistic effect between iron oxides and carbides were investigated using in-situ X-ray diffraction (in-situ XRD). The physiochemical properties of catalyst were characterized by H2-TPR and CO/H2-TPSR-MS. When the reducing environment is H2, Na promoter inhibited the reduction of Fe2O3. However, when the reducing atmosphere is syngas (CO/H2 = 1:2), a suitable amount of Na promoter decreased the reduction and activation temperatures, and increased the iron carbide concentration. The selectivity of light olefins increased from 0.3% to 20.2%, and CO2 conversion increased from 7.3% to 25.8% when syngas was used as the reducing gas compared to using H2 as the reducing gas. Compared with pure Fe2O3, the CH4 selectivity of Na modified Fe2O3 decreased from 43.2% to 14.9%, while the selectivity of C5+ increased from 7.8% to 37.0%, owing to the fact that the Fe5C2 content increased from 8.5% to 38.4%. The ratio of Fe3O4 to Fe5C2 in the catalyst could be effectively controlled by changing the reducing atmosphere and the amount of Na promoter, thereby improving the CO2 hydrogenation activity and target product selectivity.

Effect of alkalis (Li, Na, and K) on precipitated iron-based catalysts for high-temperature Fischer-Tropsch synthesis

Alkalis (Li, Na, and K) decorated FeMnZr catalysts prepared by coprecipitation and impregnation methods were used to investigate the effects of three alkali metal promoters and promoter loading (for Na and K) on the iron-based catalyst for high-temperature Fischer-Tropsch synthesis (HTFT). The results showed that alkalis donated electrons to iron species, which promoted CO dissociative adsorption while suppressing hydrogen adsorption, then boosted the selectivity to light olefins and the improvement was enhanced with the increase of the atomic number of alkali metals and the content of alkali metals. Moreover, compared to alkalis-free catalysts, alkalis-promoted catalysts facilitated the formation of χ-Fe5C2 and ɛ’-Fe2.2C. In alkalis decorated catalysts, the χ-Fe5C2 content decreased and the ɛ’-Fe2.2C content increased with increasing basicity of the catalyst surface. In addition, compared with χ-Fe5C2, ɛ’-Fe2.2C has a stronger CC coupling ability and promotes chain growth more. Compared to Li and Na promoters, K was easier to facilitate the formation of ɛ’-Fe2.2C due to its strongest basicity and CO dissociative adsorption ability. The lowest CH4 and highest C5+ selectivity were accompanied by the highest content of ɛ’-Fe2.2C on K-promoted catalysts, which suggested that ɛ’-Fe2.2C had outstanding CC coupling ability.

A Review on the Water‐Gas Shift Reaction over Nickel‐Based Catalysts

AbstractRecent advances in supported nickel catalysts for the water‐gas shift (WGS) reaction are reviewed, focusing on the structure‐mechanism relationships. The WGS reaction can proceed via the redox, carboxyl, and formate pathways over the supported nickel catalysts. However, a discrepancy exists between the mechanism‐level understanding and catalyst design principles in literature. In this review, we summarized the mechanism‐structure relationship of nickel‐based catalysts, emphasizing the effects of the formation of alloy, modification of the support or addition of alkali metal promoters on the CO adsorption and the H2O dissociation in the process of WGS reaction. Future research is suggested to systematically investigate the reaction mechanism &amp; kinetics for different catalyst structures. In addition, the manipulation of strong metal‐support interactions and the development of new types of supports are prospective directions.

Unveiling the Origin of Alkali Metal (Na, K, Rb, and Cs) Promotion in CO2 Dissociation over Mo2C Catalysts.

Molybdenum carbide (Mo2C) is a promising and low-cost catalyst for the reverse water−gas shift (RWGS) reaction. Doping the Mo2C surface with alkali metals can improve the activity of CO2 conversion, but the effect of these metals on CO2 conversion to CO remains poorly understood. In this study, the energies of CO2 dissociation and CO desorption on the Mo2C surface in the presence of different alkali metals (Na, K, Rb, and Cs) are calculated using density functional theory (DFT). Alkali metal doping results in increasing electron density on the Mo atoms and promotes the adsorption and activation of CO2 on Mo2C; the dissociation barrier of CO2 is decreased from 12.51 on Mo2C surfaces to 9.51–11.21 Kcal/mol on alkali metal-modified Mo2C surfaces. Energetic and electronic analyses reveal that although the alkali metals directly bond with oxygen atoms of the oxides, the reduction in the energy of CO2 dissociation can be attributed to the increased interaction between CO/O fragments and Mo in the transition states. The abilities of four alkali metals (Na, K, Rb, and Cs) to promote CO2 dissociation increase in the order Na (11.21 Kcal/mol) < Rb (10.54 Kcal/mol) < Cs (10.41 Kcal/mol) < K (9.51 Kcal/mol). Through electronic analysis, it is found that the increased electron density on the Mo atoms is a result of the alkali metal, and a greater negative charge on Mo results in a lower energy barrier for CO2 dissociation.

Unveiling the origin of alkali metal promotion in CO2 methanation over Ru/ZrO2

Alkali metals are used as promoters in a broad range of catalytic reactions involving supported metal catalysts, and the origin of their promotional effects has become one of the fundamental questions in heterogeneous catalysis. However, a thorough understanding of the promotional mechanism is still unclear. Combining experiments and theory, the effects of alkali metals on the reactivity of CO2 methanation reaction over Ru/ZrO2, a crucial reaction for CO2 utilization is explored. The conventionally assumed electron enrichment of Ru is not the decisive factor for the promotion. Rather, Na promotion facilitate the adsorption and dissociation of CO on the local interfacial Ru sites of Ru/ZrO2, which is the key step of CO2 methanation process. The feasible dissociation of CO on the alkali metal promoted Ru/ZrO2 originates from the enhanced electron back-donation from the interfacial Ru sites, which leads to more than an order of magnitude increase in CO2 conversion activity.

Identifying Performance Descriptors in CO2 Hydrogenation over Iron-Based Catalysts Promoted with Alkali Metals.

Alkali metal promoters have been widely employed for preparation of heterogeneous catalysts used in many industrially important reactions. However, the fundamentals of their effects are usually difficult to access. Herein, we unravel mechanistic and kinetic aspects of the role of alkali metals in CO2 hydrogenation over Fe‐based catalysts through state‐of‐the‐art characterization techniques, spatially resolved steady‐state and transient kinetic analyses. The promoters affect electronic properties of iron in iron carbides. These carbide characteristics determine catalyst ability to activate H2, CO and CO2. The Allen scale electronegativity of alkali metal promoter was successfully correlated with the rates of CO2 hydrogenation to higher hydrocarbons and CH4 as well as with the rate constants of individual steps of CO or CO2 activation. The derived knowledge can be valuable for designing and preparing catalysts applied in other reactions where such promoters are also used.

Computational insights into promoting effects of alkali metals, Re, and Cl for silver catalysts of ethylene epoxidation

Abstract The effects of Re oxospecies, Cl, and alkali metal (AM = Li, Na, K, Rb, Cs) promoters for silver catalysts of ethylene epoxidation are considered using the DFT approach. The formation of Ag-bound AMReOx surface complexes that affect the catalyst performance is demonstrated. The interplays between silver, alkali metals, and anionic promoters are discussed. The Li-based systems mostly affect the catalyst activity while other alkali metals additionally affect the selectivity towards ethylene oxide in a varying extent. The Rb dopant shows potential as a Cs substitute or co-promoter. The facile composition–performance descriptor comprising the correlation of the substrate binding energy and charge over oxygen atom is proposed. The results obtained can be used in the applied designing of Ag-based epoxidation catalysts.

Theoretical Insights into Morphologies of Alkali-Promoted Cobalt Carbide Catalysts for Fischer–Tropsch Synthesis

Co2C catalysts were found to be structure-sensitive during Fischer–Tropsch synthesis (FTS), and reaction-induced Co2C nanoprisms exposing the (101) and (020) facets exhibited superior olefin selectivity, low methane selectivity, and high activity under mild conditions. Alkali metal promoters benefit the formation and stabilization of Co2C nanoprisms, although mechanistic understanding and theoretical support are lacking due to the great complexity of this catalytic reaction and the difficulty in characterizing the detailed structural changes. Here, density functional theory (DFT) calculations and ab initio atomistic thermodynamics simulations are combined to elucidate the “promoter–structure” relationship of Co2C catalysts decorated with different alkali metal promoters. Co- and C-terminated and stoichiometric low-index surfaces including (020), (101), (111), (011), and (110) are considered. Evolution of the equilibrium morphology versus K2O coverage (θK2O) and carbon chemical potential (μC) as determined by the temperature, pressure, and the H2/CO ratio are predicted. We find that increasing θK2O facilitates the preferential exposure of the (020) and (101) facets with different terminations at diverse μC, which are the active surfaces for Fischer–Tropsch to olefins (FTO). For θK2O = 1/6 ML, these two surfaces are predicted to cover 100, 53.4, and 48.4% of the exposed surface area at μC of −7.5, −8.5, and −9.5 eV, respectively, compared with 8.6, 18.3, 26.2% without this promoter. The dominant exposure of these two facets explains the experimentally observed structure of Co2C nanoprisms with a parallelepiped shape. Additionally, the promotional effect extends the preference of most Co- and C-terminated facets over stoichiometric facets to a larger range of μC. Furthermore, Na, K, and Rb promoters are predicted to have stronger effects than Li in stabilizing these two facets, which is also consistent with available experimental observations. Insights from this theoretical work provide a rational understanding of the promotional effect of alkali metals on the morphology of the Co2C catalyst, which may facilitate the design of more efficient FTO catalysts with controlled surface structures.