Highly active K-promoted Cu/β-Mo2C catalysts for reverse water gas shift reaction: Effect of potassium

Xu, Jun; Gong, Xingxing; Hu, Ruilin; Liu, Zhao‐Tie

doi:10.1016/j.mcat.2021.111954

Cited by 19 publications

(19 citation statements)

References 53 publications

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“…To understand the origin of enhanced catalytic performance of Mo atomic sites compared to that of Mo bulk-based catalysts, we compared Mo/NC with β-Mo 2 C, which has been widely reported for the RWGS reaction among Mobased catalysts, [30,[39][40][41][42] in terms of the reactivity of adsorbed CO which was reported as the key descriptor to affect selective CO formation. [43] We found that the CO* desorption energies from the CO* + OH* + H* reaction on Mo/NC and Mo 2 C(001) surfaces were À 0.47 eV and 1.06 eV, respectively (Figure S15), indicating that CO* can be easily liberated from Mo/NC.…”

Section: Methodsmentioning

confidence: 99%

Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

et al. 2022

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The design of efficient non-noble metal catalysts for CO 2 hydrogenation to fuels and chemicals is desired yet remains a challenge. Herein, we report that single Mo atoms with a MoN 3 (pyrrolic) moiety enable remarkable CO 2 adsorption and hydrogenation to CO, as predicted by density functional theory studies and evidenced by a high and stable conversion of CO 2 reaching about 30.4 % with a CO selectivity of almost 100 % at 500 °C and very low H 2 partial pressure. Atomically dispersed MoN 3 is calculated to facilitate CO 2 activation and reduces CO 2 to CO* via the direct dissociation path. Furthermore, the highest transition state energy in CO formation is 0.82 eV, which is substantially lower than that of CH 4 formation (2.16 eV) and accounts for the dominant yield of CO. The enhanced catalytic performances of Mo/NC originate from facile CO desorption with the help of dispersed Mo on nitrogen-doped carbon (Mo/NC), and in the absence of Mo nanoparticles. The resulting catalyst preserves good stability without degradation of CO 2 conversion rate even after 68 hours of continuous reaction. This finding provides a promising route for the construction of highly active, selective, and robust single-atom non-precious metal catalysts for reverse water-gas shift reaction.

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Section: Methodsmentioning

confidence: 99%

Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

et al. 2022

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“…[24] To address this issue, we modified CoÀ C with K + which is known to lower the CO binding energy. [25][26][27] The K + À CoÀ C catalyst was prepared by drop-casting KNO 3 into aspyrolyzed CoÀ C and then treating it in H 2 at 500 °C. Increasing the added amount of KNO 3 from 0.2 wt % the mass of as-pyrolyzed CoÀ C to 10 wt % improves CO selectivity while retaining the production rate, whereas further increasing it to 30 wt % does not change the selectivity or activity (Figure S20).…”

Section: Zuschriftenmentioning

confidence: 99%

“…Notably, K + modification increases the activation energy substantially from 54.3 kJ mol À 1 to 90.0 kJ mol À 1 (Figure S18). This is likely due to suppressed H 2 adsorption, [25][26][27] which is also responsible for the improved selectivity for CO (as opposed to further hydrogenated CH 4 ). Compared with other catalysts, [14,18,20,29] the superior performance of K + À CoÀ C likely originates from its improved photothermal conversion efficiency and increased exposure of Co sites.…”

Section: Zuschriftenmentioning

confidence: 99%

“…À CoÀ C catalyst still maintains a high CO selectivity of > 95 % while achieving a high CO 2 conversion of � 25 % (Figure 4a), benefited from the K + modification suppressing CO and H 2 adsorption. [25][26][27] The simultaneously high CO 2 conversion and CO selectivity of K + À CoÀ C motivated us to pursue even higher CO 2 conversion by increasing the H 2 / CO 2 ratio. Unfortunately, CO 2 conversion was not effectively improved because increasing the H 2 /CO 2 ratio leads to decreased CO 2 partial pressure (the total pressure is kept at 1 atm) which in turn decreases the reaction rate.…”

Section: Zuschriftenmentioning

confidence: 99%

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Solar‐Driven CO₂ Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

Wang

Shang

et al. 2023

Angewandte Chemie

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Photothermal CO2 reduction is one of the most promising routes to efficiently utilize solar energy for fuel production at high rates. However, this reaction is currently limited by underdeveloped catalysts with low photothermal conversion efficiency, insufficient exposure of active sites, low active material loading, and high material cost. Herein, we report a potassium‐modified carbon‐supported cobalt (K+−Co−C) catalyst mimicking the structure of a lotus pod that addresses these challenges. As a result of the designed lotus‐pod structure which features an efficient photothermal C substrate with hierarchical pores, an intimate Co/C interface with covalent bonding, and exposed Co catalytic sites with optimized CO binding strength, the K+−Co−C catalyst shows a record‐high photothermal CO2 hydrogenation rate of 758 mmol gcat−1 h−1 (2871 mmol gCo−1 h−1) with a 99.8 % selectivity for CO, three orders of magnitude higher than typical photochemical CO2 reduction reactions. We further demonstrate with this catalyst effective CO2 conversion under natural sunlight one hour before sunset during the winter season, putting forward an important step towards practical solar fuel production.

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“…The modification of Mo 2 C with alkali metals changes the structural and electronic properties of these catalysts and promotes the performances of Mo 2 C in CO 2 conversions [ 25 , 26 , 27 , 28 , 29 ]. For example, the addition of 2 wt% K to Mo 2 C/γ-Al 2 O 3 increases the CO selectivity to 95% from 73.5% [ 30 ], and the incorporation of K into Cu/Mo 2 C results in high CO 2 dissociation activity (almost 1.5 times higher than Cu/Mo 2 C) but also reduces H 2 adsorption, thus resulting in a low H 2 /CO x ratio and low CH 4 production [ 31 ]. The CO selectivity of Cs-Mo 2 C, which can reach 100% at low-temperatures (400 to 500 °C), is a result of increased electron transfer from Cs to Mo, thus favoring CO selectivity [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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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.

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Highly active K-promoted Cu/β-Mo2C catalysts for reverse water gas shift reaction: Effect of potassium

Cited by 19 publications

References 53 publications

Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

Solar‐Driven CO₂ Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

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

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Highly active K-promoted Cu/β-Mo2C catalysts for reverse water gas shift reaction: Effect of potassium

Cited by 19 publications

References 53 publications

Single‐Atom Molybdenum‐N3 Sites for Selective Hydrogenation of CO2 to CO

Single‐Atom Molybdenum‐N3 Sites for Selective Hydrogenation of CO2 to CO

Solar‐Driven CO2 Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

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

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Product

Resources

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Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

Single‐Atom Molybdenum‐N₃ Sites for Selective Hydrogenation of CO₂ to CO

Solar‐Driven CO₂ Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure