The reverse water-gas shift reaction (RWGSR), a crucial stage in the conversion of abundant CO2 into chemicals or hydrocarbon fuels, has attracted extensive attention as a renewable system to ...synthesize fuels by non-traditional routes. There have been persistent efforts to synthesize catalysts for industrial applications, with attention given to the catalytic activity, CO selectivity, and thermal stability. In this review, we describe the thermodynamics, kinetics, and atomic-level mechanisms of the RWGSR in relation to efficient RWGSR catalysts consisting of supported catalysts and oxide catalysts. In addition, we rationally classify, summarize, and analyze the effects of physicochemical properties, such as the morphologies, compositions, promoting abilities, and presence of strong metal-support interactions (SMSI), on the catalytic performance and CO selectivity in the RWGSR over supported catalysts. Regarding oxide catalysts (i.e., pure oxides, spinel, solid solution, and perovskite-type oxides), we emphasize the relationships among their surface structure, oxygen storage capacity (OSC), and catalytic performance in the RWGSR. Furthermore, the abilities of perovskite-type oxides to enhance the RWGSR with chemical looping cycles (RWGSR-CL) are systematically illustrated. These systematic introductions shed light on development of catalysts with high performance in RWGSR.
Evaluating the delamination process in the synthesis of MXenes (2D transition metal carbides and nitrides) is critical for their development and applications. However, the preparation of large ...defect‐free MXene flakes with high yields is challenging. Here, a power‐focused delamination (PFD) strategy is demonstrated that can enhance both the delamination efficiency and yield of large Ti3C2Tx MXene nanosheets through repetitive precipitation and vortex shaking processes. Following this protocol, a colloidal concentration of 20.4 mg mL–1 of the Ti3C2Tx MXene can be achieved after five PFD cycles, and the yield of the basal‐plane‐defect‐free Ti3C2Tx nanosheets reaches 61.2%, which is 6.4‐fold higher than that obtained using the sonication–exfoliation method. Both nanometer‐thin devices and self‐supporting films exhibit excellent electrical conductivities (≈25 000 and 8260 S cm‐1 for a 1.8 nm thick monolayer and 11 µm thick film, respectively). Hydrodynamic simulations reveal that the PFD method can efficiently concentrate the shear stress on the surface of the unexfoliated material, leading to the exfoliation of the nanosheets. The PFD‐synthesized large MXene nanosheets exhibit superior electrical conductivities and electromagnetic shielding (shielding effectiveness per unit volume: 35 419 dB cm2 g–1). Therefore, the PFD strategy provides an efficient route for the preparation of high‐performance single‐layer MXene nanosheets with large areas and high yields.
A new method for the preparation of large 2D Ti3C2Tx MXene nanosheets is reported. The method is based on conventional etching followed by repetitive precipitation and vortex shaking process, which efficiently transfer the mechanical energy for exfoliation. Consequently, large defect‐free sheets that show an excellent electromagnetic shielding performance are produced with high yields.
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•Pd clusters (∼0.59 nm) anchored to nanosized TiO2 (∼8 nm) was prepared at a high Pd loading (∼5 wt%).•Theoretical calculation and experimental research confirmed the presence of ...strong EMSIs between TiO2 and Pd.•Strong EMSIs enhanced the catalytic reactivity for the hydrogenation of resorcinol.•Strong EMSIs favored a nonplanar form of resorcinol to improve 1,3-cyclohexanedione selectivity.
Strong electronic metal-support interactions (EMSIs) present in supported metal catalysts play a crucial role in determining their catalytic performances. In this study, we demonstrate the successful utilization of nanosized TiO2 (∼8 nm) as a carrier to achieve highly dispersed Pd clusters (∼0.59 nm) with robust EMSIs, even at a high Pd loading of 5 wt%. The presence of surface defects in nanosized TiO2 facilitates the anchoring of Pd clusters onto the support surface, leading to enhanced EMSIs between TiO2 and Pd. The prepared Pd/TiO2 catalyst delivers drastically improved catalytic property in the hydrogenation of resorcinol (RES), achieving >99 % conversion and >99 % selectivity towards 1,3-cyclohexanedione (1,3-CHD) within 60 min at 2 MPa hydrogenation pressure and 373 K. This performance is superior to that of Pd nanoparticles on TiO2 support with a larger particle size of ∼200 nm, which only achieves 80 % conversion and 37 % selectivity to 1,3-CHD. Both experimental data and theoretical calculations confirm that TiO2 donates electrons to the Pd clusters, thereby enhancing the hydrogenation properties of RES. Specifically, the electron-deficient TiO2 favors the adsorption and activation of phenoxy anion, while the electron-enriched Pd induces a nonplanar conformation of the adsorbed RES molecules and facilitates the electrophilic attack of adsorbed hydrogen on RES by weakening the strength of hydrogen adsorption. Furthermore, the Pd/TiO2 catalyst exhibits excellent recyclability, maintaining its efficiency over 7 cycles, attributed to the stabilizing effect of nanosized TiO2 on Pd clusters. The simple design strategy presented in this work enables the development of supported metal catalysts with significant EMSIs and is expected to attract more attention in future research.
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The preparation of an environmentally friendly hydroxylated Ti3C2/Ti3AlC2 catalyst avoids the use of hydrofluoric acid and exhibits a highly active oxidative desulfurization catalyst.
...•An h-Ti3C2/Ti3AlC2 catalyst was prepared via an alkaline etching process.•Ti–OH and Ti–O active sites were concentrated on the catalyst surface.•The catalyst showed high activity for aerobic oxidative desulfurization.•The enhanced activity was attributed to the continuous generation of •OH and •O2−.•The catalyst could be reused 8 times without any significant loss of activity.
Hydrofluoric acid is inevitable in most preparation schemes for two-dimensional MXene materials, which is dangerous and environmentally hazardous. Herein, hydroxylated Ti3C2/Ti3AlC2 (h-TC/TAC) catalysts were prepared via an alkaline etching process using a safer, more environmentally friendly alkali. After preferentially forming a hydroxylated Ti3C2 MXene layer on the surface of Ti3AlC2, Ti-C bonds on the surface were partially hydrolyzed, which exposed more active sites. Alkaline etching modulated the chemical composition and electronic structure of the catalyst surface, thus concentrating the active sites on the surface, which improved the activation efficiency and substrate conversion. For the aerobic oxidative desulfurization of a model fuel with a sulfur content of 220 ppm, the prepared catalyst exhibited a desulfurization rate of up to 99% when using air as a cheap molecular oxygen source. The enhanced activity of the h-TC/TAC catalyst was attributed to the continuous activation of molecular oxygen to form •OH and •O2–. Moreover, because the main structure of Ti3AlC2 was maintained, the catalyst could be recycled 8 times without a significant decrease in activity. This work not only shows the potential of alkaline etching for preparing MXene materials but also provides an important example of the thermocatalytic application of MXene and MAX phase materials.
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•The assembly of ultrathin CoOOH nanosheets into the PANI network can be realized as OER catalyst.•The nitrogen species derived from PANI can work as bridging sites to coordinate with ...Co metal ions.•The electron delocalization of Co/PANI HNSs can regulate its own electronic structural states.•The Co/PANI HNSs presents a hierarchical porous with both structure of mesopores and macropores.•The high-stability Co/PANI HNSs catalyst can afford a low overpotential with a small Tafel slope.
Polyaniline (PANI)-based composite materials have shown to be promising candidates for oxygen evolution reaction (OER) electrocatalysts because of their non-ignorable merits of conductivity, flexibility, durability and environmental friendly. Herein, we develop a facile strategy to realize in-situ assembly of CoOOH nanosheets into the PANI network, which is denoted as Co/PANI HNSs for OER performance. The nitrogen species derived from PANI building blocks can work as bridging sites to preferentially coordinate with Co metal ions, which impart coupling effects between CoOOH nanosheets and PANI as well as the structure stability. Besides the Co-N coordination, the occurred electron delocalization between Co d-orbitals and PANI π-conjugated ligands can also modulate the electronic structural states of Co/PANI HNSs, enabling the efficient interfacial electron transfer from CoOOH to PANI. In addition, the Co/PANI HNSs possesses a hierarchical porous with both structure of mesopores and macropores that allows electrolyte to be more efficiently transported to the highly oxidative active sites, resulting in fast reaction kinetics. In recognition of these advanced structural characteristics, the Co/PANI HNSs electrocatalyst can give a low overpotential of 291 mV at an anodic current density of 10 mA cm−2 and a small Tafel slope of 54 mV dec−1 in 1 M KOH electrolyte as well as a good durability.
•Low-coordinated Pt was fabricated via dealloying of Ni-Pt alloy.•High m-DNB to m-PDA hydrogenation activity due to the effect of low coordination.•Effectively synthesize various aromatic amines at ...ambient temperature and pressure.
Catalytic hydrogenation of aromatic nitro-compounds to corresponding aromatic amines is an environmental-friendly transformation for the production of dyes and pigments in industrial. Herein, an efficient low-coordinated Pt derived from Ni-Pt alloy archored on silica has been fabricated via dealloying process. Transmission electron microscopy (TEM) analysis confirmed an equivalent metal particle size to the reference dense Pt. Additionally, the characterizations revealed that the generation of unsaturated coordination in the resultant material leads to enhanced active surface area, increased fraction of low-coordinated and electron-enriched Pt. The as-prepared low-coordinated Pt catalyst was applied for liquid-phase m-dinitrobenzene (m-DNB) hydrogenation. Under the reaction conditions of ambient temperature, atmospheric pressure and m-DNB/Pt molar ratio of 140, both the m-DNB conversion and the selectivity to m-phenylenediamine (m-PDA) reached 99% within 2 h, superior to those observed over the reference dense Pt and the reported Pt-based catalysts. The enhanced catalytic properties were attributed to the promotional effect of unsaturated coordinated structure, which provided more Pt active sites with low coordination number and high electron density. This study demonstrates the importance of unsaturated coordination in metallic catalysts and establishes a powerful protocol for the design of an effective metal catalyst for the hydrogenation of a range of nitroaromatic compounds.
MXenes are currently one of the most widely studied two-dimensional materials due to their properties. However, obtaining highly dispersed MXene materials in organic solvent remains a significant ...challenge for current research. Here, we have developed a method called the tuned microenvironment method (TMM) to prepare a highly concentrated Ti3C2T x organic solvent dispersion by tuning the microenvironment of Ti3C2T x . The as-proposed TMM is a simple and efficient approach, as Ti3C2T x can be dispersed in N,N-dimethylformamide and other solvents by stirring and shaking for a short time, without the need for a sonication step. The delaminated single-layer MXene yield can reach 90% or greater, and a large-scale synthesis has also been demonstrated with TMM by delaminating 30 g of multilayer Ti3C2T x raw powder in a one-pot synthesis. The synthesized Ti3C2T x nanosheets dispersed in an organic solvent possess a clean surface, uniform thickness, and large size. The Ti3C2T x dispersed in an organic solvent exhibits excellent oxidation resistance even under aerobic conditions at room temperature. Through the experimental investigation, the successful preparation of a highly concentrated Ti3C2T x organic solvent dispersion via TMM can be attributed to the following factors: (1) the intercalation of the cation can lead to the change in the hydrophobicity and surface functionalization of the material; (2) proper solvent properties are required in order to disperse MXene nanosheets well. To demonstrate the applicability of the highly concentrated Ti3C2T x organic solvent dispersion, a composite fiber with excellent electrical conductivity is prepared via the wet-spinning of a Ti3C2T x (dispersed in DMF) and polyacrylonitrile mixture. Finally, various types of MXenes, such as Nb2CT x , Nb4C3T x , and Mo2Ti2C3T x , can also be prepared as highly concentrated MXene organic solvent dispersions via TMM, which proves the universality of this method. Thus, it is expected that this work demonstrates promising potential in the research of the MXene material family.
MXenes are currently one of the most widely studied two-dimensional materials due to their properties. However, obtaining highly dispersed MXene materials in organic solvent remains a significant ...challenge for current research. Here, we have developed a method called the tuned microenvironment method (TMM) to prepare a highly concentrated Ti
C
T
organic solvent dispersion by tuning the microenvironment of Ti
C
T
. The as-proposed TMM is a simple and efficient approach, as Ti
C
T
can be dispersed in
,
-dimethylformamide and other solvents by stirring and shaking for a short time, without the need for a sonication step. The delaminated single-layer MXene yield can reach 90% or greater, and a large-scale synthesis has also been demonstrated with TMM by delaminating 30 g of multilayer Ti
C
T
raw powder in a one-pot synthesis. The synthesized Ti
C
T
nanosheets dispersed in an organic solvent possess a clean surface, uniform thickness, and large size. The Ti
C
T
dispersed in an organic solvent exhibits excellent oxidation resistance even under aerobic conditions at room temperature. Through the experimental investigation, the successful preparation of a highly concentrated Ti
C
T
organic solvent dispersion
TMM can be attributed to the following factors: (1) the intercalation of the cation can lead to the change in the hydrophobicity and surface functionalization of the material; (2) proper solvent properties are required in order to disperse MXene nanosheets well. To demonstrate the applicability of the highly concentrated Ti
C
T
organic solvent dispersion, a composite fiber with excellent electrical conductivity is prepared
the wet-spinning of a Ti
C
T
(dispersed in DMF) and polyacrylonitrile mixture. Finally, various types of MXenes, such as Nb
CT
, Nb
C
T
, and Mo
Ti
C
T
, can also be prepared as highly concentrated MXene organic solvent dispersions
TMM, which proves the universality of this method. Thus, it is expected that this work demonstrates promising potential in the research of the MXene material family.
One-pot dynamic kinetic resolution (DKR) has garnered considerable attention for its potential to generate enantiomerically pure compounds in high yields and simplifying operation. However, the ...challenge lies in achieving compatibility between enzymes and metals due to their distinct operating conditions. In this study, we present a novel cascade catalytic platform for the DKR of amines to address this issue. Pd nanoparticles were immobilized on lysine-decorated lipase nanogels, forming isolated metal-enzyme catalysts. The microwave-assisted one-pot DKR of amines was carried out under non-pressurized conditions at 50 °C for 5 h. The metal-enzyme nanogel biochemical composite exhibited excellent performances, with a high conversion rate of 98% and enantiomeric excess values exceeding 99%. This innovative approach demonstrates the potential of constructing a multifunctional metalloenzyme catalytic platform with a distinctive three-dimensional structure, which offers promising prospects for DKR applications.
The metal-enzyme nanogel biochemical composite exhibits excellent catalytic performance in non-pressurized microwave conditions at 50 °C, achieving an outstanding 98% conversion rate and ee value＞99%. Display omitted
•A novel Pd@CALB-Lys-nanogels cascade catalytic platform was developed.•Lysine modification reduces the size of enzyme nanogels and can promotes the dispersion of metal.•The catalyst exhibited high activity and selectivity in microwave-assisted Dynamic Kinetic Resolution.•The catalyst can spontaneously catalyze reactions at mild temperatures without the need for hydrogen pressure.
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