Search

CuO/CeO2 catalysts were widely studied as an alternative to precious metal catalysts, and the Cu–Ce synergy was essential to improve the catalytic performance. In this paper, the effects of CuO loading on Cu–Ce synergy in CuO/CeO2 nanorod catalysts and their performance in toluene combustion were systematically investigated. It was found that non-equilibrium plasma facilitated the dispersion of CuO active species on the CeO2 surface. With the increase of the CuO loading from 1 wt% to 4 wt%, the Cu–Ce synergistic effect was gradually improved, which generated Cu+/Cu2+ and Ce3+/Ce4+ redox electron pairs. The highest oxygen vacancy concentration and Cu+ content of CuCe-4 (4 wt%) resulting from strong Cu–Ce synergy accelerated the activation of chemisorbed oxygen and consequently improved the efficiency of toluene catalytic combustion. [ABSTRACT FROM AUTHOR]

The production of ammonia under ambient conditions has been a long-standing challenge for the chemical industry. The electroreduction of nitrate presents a promising solution for nitrate wastewater treatment and decentralized ammonia production. However, traditional Ag-based catalysts suffer from nitrate-to-nitrite conversion, leading to toxicity concerns and hampering ammonia preparation. In this study, we synthesized an innovative Ag–Cu–P catalyst that effectively tunes the d-band centre and electronic structure. The catalyst exhibited a remarkable NH4+ yield rate of 566.30 μmol cm−2 h−1 at −0.3 V (vs. RHE), reducing nitrite content to below the drinking water standard. Characterization results revealed a distinctive fern leaf-like morphology, providing an expanded active surface area. The challenge of facile nitrate conversion to nitrite on Ag-based catalysts has been addressed through the implementation of electronic structure modulation in this work. Theoretical calculations confirmed the substantial reduction in the energy barrier by modulating the d-band centre and electronic structure, facilitating the conversion of nitrite to ammonia. The regulation and analysis of d-band centres yielded valuable insights for catalyst material design. Meanwhile, direct evidence for potential intermediates has also been presented through in situ spectroscopy. These findings hold significant potential for practical applications, such as enhanced wastewater treatment and decentralized ammonia production, and provide support in the pressing need for sustainable ammonia synthesis under ambient conditions. [ABSTRACT FROM AUTHOR]

The synthesis of a hierarchical SSZ-13 zeolite with mesopores and micropores is one of the most effective strategies to overcome the diffusion limitation imposed by the micropores of SSZ-13 in reactions involving bulky reactants or intermediates. A zeolite with nanosheet morphology possesses the advantages of large inter-sheet mesopore volume, more accessible acid sites and short diffusion path lengths. Nevertheless, only a few works focused on the synthesis of the nanosheet-assembled SSZ-13 zeolite. In this work, a nanosheet-assembled hierarchical SSZ-13-TP0.03 (thickness of 20 nm) zeolite was synthesized in a seed-assisted synthesis system by coupling a small amount of N, N, N-trimethyl-1-adamantylammonium hydroxide (TMAdaOH) with octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride (TPOAC). In this strategy, the Si/Al ratio of the initial gel, seed, TPOAC and TMAdaOH amount in the synthesis system and the synergistic effects among them lead to the synthesis of SSZ-13 samples with various textural properties and morphologies. The distinct textural properties and morphologies of SSZ-13 result in the preparation of Pt/SSZ-13 catalysts with varied Pt dispersions. The catalyst, Pt supported on the nanosheet-assembled hierarchical SSZ-13 (Pt/SSZ-13-TP0.03), exhibits higher hydrogenation ability than its corresponding catalyst, Pt supported on microporous or hierarchical SSZ-13 in the hydrogenation of naphthalene. [ABSTRACT FROM AUTHOR]

Bi-based materials are promising catalysts for electrochemical reduction of carbon dioxide (CO2) to formate, but remain challenging in terms of activity and stability. Herein, we report the facile synthesis of Zn-doped Bi nanosheets (Zn–Bi NSs) as a highly active and robust catalyst for electrochemical reduction of CO2 to formate. Specifically, the Zn–Bi NS catalyst can be obtained using a hydrothermal method to prepare a Zn-decorated Bi2O2CO3 nanosheet followed by electrochemical reduction treatment. The as-prepared catalyst exhibits a remarkable formate faradaic efficiency of 94.6% and a high formate current density of 40.5 mA cm−2 at −1.2 V vs. reversible hydrogen electrode (RHE). In particular, the faradaic efficiency of formate remained at above 90% over a wide potential window from −0.8 to −1.2 V vs. RHE. In the H-type electrolytic cell, the Zn–Bi NS catalyst can be operated stably for 10 h at a cathode potential of −1.0 V vs. RHE with good retention of the physical phase. [ABSTRACT FROM AUTHOR]

Carbon-supported non-precious metal catalysts with highly exposed active sites have great potential for applications in the hydrogenation reduction of nitro compounds. Herein, a strategy for the preparation of carbon-supported Mo-based catalysts (Mo@C/MC) is proposed. Protein–Mo ion networks are first coated on the surface of microsphere carbons (MC). The coated MC employed as a precursor is then pyrolyzed to produce carbon-supported Mo-based catalysts. Notably, neither pore-forming agents nor post-treatment is required in the preparation of the catalyst. The active sites tend to disperse uniformly on the surface of the carbon matrix, facilitating the exposure of the active sites of the catalyst. The as-prepared catalyst Mo@C/MC shows high conversion (>99%) and selectivity (>98%) for the hydrogenation of nitro compounds under mild reaction conditions (100 °C, 5 bar H2). [ABSTRACT FROM AUTHOR]

Developing low-cost and efficient catalysts for the oxidation of formaldehyde (HCHO) is crucial for preservation of the environment. The main challenge of this study is how to develop an efficient, stable, and inexpensive catalyst that can oxidize HCHO at low temperatures. Herein, the reduced Mn-doped cobalt tetroxide R-MnxCo3−xO4 catalyst was prepared by simple co-precipitation and annealing treatment followed by reduction of NaBH4. The prepared R-MnxCo3−xO4 showed remarkable enhanced activity for HCHO oxidation at low temperature. The R-MnCo2O4 catalyst can oxidize and decompose 79% of HCHO at a low temperature of 50 °C and exhibits excellent catalytic stability. The improved catalytic activity can be attributed to the increase in oxygen vacancy concentration and the improvement in redox performance. The TGA test shows that the content of oxygen vacancies in the R-MnCo2O4 catalyst can reach 5.77% (atomic ratio). The H2-TPR, O2-TPD and O2-TPO tests indicated that the surface oxygen vacancies can promote oxygen mobility and facilitate the formation of reactive oxygen species during the formaldehyde catalytic oxidation process. This study reveals the importance of surface oxygen vacancies in improving the catalytic oxidation activity of catalysts, providing possibilities for the development of high-performance catalysts through atomic doping and reduction modification. [ABSTRACT FROM AUTHOR]

The present study is focused on the synthesis of DHPMs by using NiCoSe2 and NiCo2S4 as heterogeneous catalysts, and they are characterized by using XRD, SEM, TEM, BET and XPS. The NiCoSe2 and NiCo2S4 catalysts proved to be the most suitable catalytic system when compared to conventionally reported catalysts in terms of yield and reaction time. NiCoSe2 and NiCo2S4 are environment-friendly catalysts and can be recycled over 5 cycles with a negligible loss in the catalytic performance. Thus, the synthesized catalysts were successfully utilized in the synthesis of biologically active DHPMs, and all compounds were characterized using mass and NMR spectroscopic techniques. [ABSTRACT FROM AUTHOR]

A potassium (K)-promoted Ru-based siliceous molecular sieve catalyst, K-nRu-MCM-41, was successfully synthesized via a hydrothermal method. The combined analysis of XRD, FT-IR and XPS data revealed that Ru exists in the framework of the molecular sieves as RuO2 species, leading to structural alterations. SEM and TEM images demonstrated that Ru doping disrupts the morphology of the molecular sieves, while K addition effectively preserves the original morphology and further enhances particle dispersion. The ammonia decomposition performance test indicated that K promotes the activity of the molecular sieve catalysts. At 450 °C and 12 000 mL gcat−1 h−1, K-4Ru-MCM-41 achieved 82.7% ammonia conversion and 253.6 mmol gRu−1 min−1 hydrogen production, respectively, which was a 7.6% increase in ammonia conversion compared with 4Ru-MCM-41. Furthermore, the K-4Ru-MCM-41 catalyst exhibited excellent reusability, maintaining its stable catalytic activity performance after 30 h. [ABSTRACT FROM AUTHOR]

A series of SO42−/TiO2 solid superacid catalysts were prepared under different conditions. The effect of different preparation conditions on the SO42−/TiO2 catalyst was investigated by evaluating the change of its crystallinity, chemical structure and acid content. The catalytic performance of the SO42−/TiO2 catalyst was evaluated by α-pinene isomerization in a continuous fixed bed reactor. When ammonia was used as the precipitation agent, the concentration of sulfuric acid impregnation solution was 2 M, and the calcination temperature was 500 °C, the activity of the SO42−/TiO2 catalyst reached the maximum, the conversion rate of α-pinene was stable at about 95%, and the selectivity of camphene reached 40%. It was found that the structure and textural properties of the SO42−/TiO2 catalyst did not change significantly after regeneration by studying the regeneration performance of the SO42−/TiO2 catalyst. [ABSTRACT FROM AUTHOR]

This study presents a pioneering nanohybrid catalyst featuring hierarchically porous dual-functional (acid–base) active sites, which is a versatile catalyst for the crucial bio-glycerol acetalization reaction. The nanohybrid catalyst demonstrated remarkable efficiency in converting bio-diesel derived waste glycerol into excellent green fuel additive 'solketal,' achieving an unprecedented yield of approximately 99%. Insights into the structural properties and the relationship between the structure and properties of the catalyst were obtained through various characterization techniques, including FTIR spectroscopy, XRD, NH3-TPD, CO2-TPD, 27Al-NMR spectroscopy, SEM, TEM, UV-Vis spectroscopy, and X-ray photoelectron spectroscopy. The hybrid catalyst shows several highly desirable properties, including enhanced acidity, a strong affinity for reactants, mesoporosity, stability, and the proximity of potent acidic and basic sites. Simplicity, cost-effectiveness, exceptional recyclability, and resistance to moisture make the synthesized MgAl-oxide/HZSM-5 (MAZ) nanohybrid catalyst an appealing candidate for potential commercial applications in bio-refinery processes. [ABSTRACT FROM AUTHOR]

Non-precious metal catalysts play a significant role in the field of hydrogenation. This study synthesized Co-BTC from cobalt nitrate hexahydrate and 1,3,5-tricarboxylic acid benzene. By changing the calcination temperature of Co-BTC in an inert atmosphere, a series of novel non-precious metal Co/C microsphere catalysts were successfully prepared. The composition and structure of the Co/C-n catalysts were characterised by FESEM, TEM, XRD, IR, XPS and BET. These results confirm that 1,3,5-benzenetricarboxylic acid provides a rich carbon matrix and metallic Co nanoparticles are generated by self-reduction on the carbon matrix. The graphite matrix formed during the calcination process has a rich pore structure and good dispersion of active components on the catalyst surface, which is very favourable for the catalytic reaction. In the hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN), the Co/C-500 catalyst showed the best catalytic performance. At 80 °C and 2 MPa H2 for 60 minutes, the conversion rate of o-CNB reached 99% and the selectivity reached 99%. When the reaction takes 5 minutes, the conversion rate reaches 10.5%, and the TOF value reaches 36.3 h−1. The Co/C-500 catalyst can be easily recycled and reused after reaction with the help of a magnetic field. Moreover, this catalyst is also effective in the selective hydrogenation of other nitroaromatic hydrocarbons containing halogen or unsaturated groups to corresponding aniline. This simple and direct synthesis method may lead to the economic production of large-scale Co/C catalysts, which is an attractive prospect for the industrial trial production of corresponding aniline. [ABSTRACT FROM AUTHOR]

Designing an efficient zeolite-introduced novel Fe-based catalyst is essential for the direct production of gasoline fuels via coupling Fischer–Tropsch synthesis (FTS) and catalytic cracking reactions. Herein, we constructed a novel Fe2O3 cage catalyst with a hierarchical porous structure, which served as FTS sites for physically mixing with porous ZSM5 to provide catalytic cracking sites. The hybrid Fe + ZSM5(27) catalyst achieved an excellent gasoline fuel (C5–C11) selectivity of 62.7 wt%, outperforming traditionally supported and physically mixed catalysts. Moreover, the aromatic content was 22.1% in terms of C5+ hydrocarbons, which was within the range of the restricted aromatic content. The enhanced catalytic performance can be attributed to the Si/Al ratio governing the oligomerization reaction. ZSM5 with a suitable Si/Al ratio can promote the oligomerization of C2–C4 olefins to produce desired C5–C11 hydrocarbons. Fe + ZSM5(27) with a Si/Al ratio of 27 demonstrated a prominent CO conversion of 93.6% with a higher C5–C11 selectivity of 62.7 wt%. This work provides a promising strategy for designing multifunctional catalysts to modulate product distribution. [ABSTRACT FROM AUTHOR]

Ni-based catalysts have been considered as an efficient anode material for urea fuel cells due to their low cost and high activity in alkaline media. Ni2P/NiCo2S4 catalyst grown on nickel foam was synthesized by hydrothermal synthesis and solid phosphating. The cathode material Pt/C was prepared using the drop-coating method, which has good oxygen reduction reaction (ORR) activity. H-type urea/O2 fuel cell was assembled and showed high energy density in alkaline solution at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) were employed to characterize the Ni2P/NiCo2S4/NF catalyst. Results confirmed the formation of 3D flower-like microspheres from Ni2P/NiCo2S4/NF catalyst nanosheets. Electrochemical testing results indicated that the Ni2P/NiCo2S4/NF catalyst-decorated electrode can effectively promote urea oxidation and plays a leading role in improving the performance of fuel cells in 1 M KOH + 0.33 M urea. The H-type urea/O2 fuel cell possesses a high power density of 0.42 mW cm−2 at a cell potential of 0.45 V. To summarize, this study introduces a cheap but efficient electrode material as an anode catalyst for constructing urea fuel cells. [ABSTRACT FROM AUTHOR]

Mg–Ba mixed oxide catalysts are synthesized using the co-precipitation method by varying the molar compositions of MgO and BaO. The catalysts' surface/structural properties are characterized by N2 physisorption, PXRD, CO2-TPD, FT-IR spectroscopy, X-ray photoelectron spectroscopy, and laser Raman spectroscopy. The characterization results showed that the insertion of Mg2+ into the BaO lattice results in the generation of stable mixed oxide solid solutions. These catalysts are evaluated for continuous glycerol transesterification with dimethyl carbonate to yield glycerol carbonate under solvent free and atmospheric pressure conditions. The activity of catalysts mainly relied on strong basic centres (c-MgO) originating from Mg and Ba of different molar ratios and the catalyst with a 3 : 1 molar ratio exhibited an excellent glycerol carbonate yield of up to 70% with nearly 100% selectivity. The activities of the catalysts are well explained based on their surface-structural integrity. The catalysts exhibited exceptional stability during the time on stream study over a period of 100 h. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFC) are a promising new energy source. However, the lack of high-performance and low-cost methanol oxidation electrocatalysts hinders their commercial application. Firstly, we successfully prepared NENU-5-derived molybdenum carbide material (Cu-MoC) via a co-precipitation and high-temperature carbonization method using a material composed of a copper-based metal–organic skeleton and a molybdenum-based carbide as the main body. Secondly, PtCu nano-alloy catalysts (Pt/Cu-MoC) were prepared using a unique, spontaneous single replacement reaction after metal–organic skeleton (MOF) carbonization. Through the synergistic effect between Pt and Cu and the strong interaction between Mo2C and PtCu, the electronic structure of the Pt is modified, the energy of the d-band center is reduced, electron exchange is accelerated, and catalytic activity is enhanced. Compared with a commercial Pt/C catalyst in alkaline environments, the Pt0.10/Cu-MoC catalyst has a better MOR catalytic activity (563.25 mA mgPt−1), which is 1.5 times higher than that of commercial Pt/C (376.67 mA mgPt−1). The Pt0.10/Cu-MoC catalyst has an onset potential for CO oxidation that is 16 mV lower than that of commercial Pt/C, indicating better resistance to CO poisoning. Exploring carbon materials derived from MOFs with excellent junction support and using them as carriers to prepare Pt-based catalysts is a practical and feasible approach. It provides a way to develop new Pt-based catalysts that perform efficient MOR. [ABSTRACT FROM AUTHOR]

Oxidative esterification of furfural to methylfuroate was conducted in base-free medium over Au catalysts supported on ZrO2, CeO2, TiO2, ZnO and Al2O3, and the Au/Al2O3 catalyst exhibited a higher activity than the other prepared catalysts. The characterization results of these Au catalysts showed that the Au/Al2O3 catalyst possessed good dispersion of Au nanoparticles and suitable surface acidity, leading to better performance of the catalyst. The effects of reaction time, reaction temperature, initial O2 pressure and catalyst dosage on the oxidative esterification of furfural over Au/Al2O3 were investigated, and furfural conversion and methylfuroate selectivity reached 99.8% and ∼100%, respectively, under the conditions of 140 °C, 1 MPa O2, 1 h and 0.2 g catalyst. Meanwhile, the furfural/methanol mole ratio in this work was as high as 1/27, which is higher than that reported in the literature and is more promising for commercial application. The catalytic performance of Au/Al2O3 was found to decrease slightly with the use time, and the aggregation of Au particles in the reaction was suggested to account for the decrease in activity. The functional mechanism of the catalyst was investigated via contrast experiments, and it was speculated that the acid sites of Al2O3 might promote the adsorption of furfural on the surface of catalyst, and Au catalyzed both steps of the oxidative esterification of furfural to methylfuroate. [ABSTRACT FROM AUTHOR]

The development of carbon-based catalysts to substitute Pt-based catalysts for the oxygen reduction reaction is highly important for promoting their practical application in energy conversion. Herein, we prepare Zn, Fe and N-codoped porous carbon (Zn/Fe-NC-x) as a cathode catalyst via a facile one-step pyrolysis predesigned bimetallic zeolitic imidazole framework. Systematic electrochemical studies demonstrated that the synthesized Zn/Fe-NC-0.5 exhibits higher electrocatalytic activity towards the oxygen reduction reaction. In particular, Zn/Fe-NC-0.5 has a smaller charge transfer resistance, larger exchange current density, and much higher open circuit potential and mainly proceeds via an efficient four-electron pathway. A microbial fuel cell equipped with the synthesized catalyst exhibited the highest maximum power density of 1954 ± 20 mW m−2. In addition, the effects of the iron doping content on the oxygen reduction reaction performance and maximum power density were evaluated: a moderate Fe doping content plays a crucial role in improving the catalytic activity, and the synergistic effect of Zn, Fe and N codoping promotes cathodic performance. In brief, Zn/Fe-NC, which has the advantages of facile synthesis, environmental friendliness and excellent electrochemical activity, is a promising Pt-alternative catalyst for the oxygen reduction reaction in air-cathode microbial fuel cells. [ABSTRACT FROM AUTHOR]

The highly efficient synthesis of benzoxazole, benzothiazole and benzimidazole has attracted much attention due to their superior biological activities. However, developing environmentally friendly and poisoning-resistant catalysts in heterogeneous catalytic systems remains a critical challenge. Herein, an atomically dispersed Co1/NC catalyst was fabricated by facile pyrolysis of a zeolitic imidazolate framework (ZnCo-ZIF). The Co1/NC catalyst exhibited excellent oxidation catalysis, sulfur-resistance and reusability performance. The mass specific activity (MSA) of Co1/NC was up to 42.0 mol2-PBO molCo−1 h−1, much higher than that of the Co/NC nano-catalyst (15.6 mol2-PBO molCo−1 h−1). Mechanism studies showed that O2 was activated by atomically dispersed Co active species to form 1O2 and ˙O2−, which were responsible for the dehydrogenation of the key imine intermediates to produce 2-phenylbenzoxazole (2-PBO). The current work represents a novel feasible strategy for the synthesis of bioactive heterocyclic compounds using efficient, stable and green heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Furfural is an industrial renewable platform chemical, which can be converted to useful furanics such as α-angelica lactone, carboxylic acids such as levulinic acid and valeric acid, or to higher carbon content products via condensation routes for producing drop-in fuel replacements and chemicals with diverse applications. These important conversion processes may be carried out in selective fashions, although they require adequate catalysts. They were successfully carried out using versatile, stable silica-wrapped niobium oxide nanostructured catalysts. For example, α-angelica lactone was converted in an integrated fashion to ethyl levulinate in 90% yield, and the esterification of levulinic and valeric acids gave ethyl levulinate in quantitative yield and ethyl valerate in 90% yield, respectively, at 140 °C. Catalytic, mechanistic and kinetic modelling studies shed light on the influence of the materials properties on the catalytic performances. These catalysts outperformed pure Nb2O5, as well as hydrothermally synthesized composites consisting of Nb2O5 nanoparticles embedded in a mesoporous siliceous matrix. [ABSTRACT FROM AUTHOR]

Lignin is composed of phenylpropyl alcohol through the C–O and C–C bonds, where β-O-4 accounts for the majority. Self-transfer hydrogenolysis (STH) is a promising method to produce valuable chemicals and fuels from lignin by cleaving the β-O-4 bond without exogenous hydrogen, but all the reported work used noble metal-based catalysts. In this work, a highly efficient Ni/C catalyst was derived from a Ni-containing metal–organic framework (Ni-MOF), and its self-transfer hydrogenolysis performance towards ether bonds in lignin model compounds was evaluated using 2-phenoxy-1-phenylethanol as a model compound in detail. It was found that the catalyst pyrolyzed under a nitrogen atmosphere at 500 °C (Ni-NDC-500) was very efficient for the reaction. Moreover, it could also catalyze the reaction of native lignin into monomers effectively without exogenous hydrogen. In addition, Ni-NDC-500 was recycled three times without an obvious reduction of the activity. [ABSTRACT FROM AUTHOR]

This study introduces a novel catalyst designated as 2.6% Co/MXene, comprising cobalt (Co) nanoparticles supported by MXene. The synthesis of the 2.6% Co/MXene catalyst involved direct pyrolysis of a composite material, composed of a Co/Zn bimetal metal–organic framework and MXene. Catalytic transfer hydrogenation of functionalized nitro compounds into the corresponding formamides employed formic acid as both the hydrogen donor and formylation agent, demonstrating remarkable activity and selectivity. Control experiments validated that Co nanoparticles served as the active sites for reductive transformation. Systematic characterization and comprehensive experiments have confirmed that the superior catalytic performance of the 2.6% Co/MXene catalyst can be attributed to the uniform distribution of Co nanoparticles, a high density of basic sites, and the 3D porous architecture of the MXene support. Furthermore, the 2.6% Co/MXene catalyst exhibited excellent recyclability, preserving its catalytic activity and selectivity across four consecutive cycles. [ABSTRACT FROM AUTHOR]

Herein, Ni–Co alloy particles embedded in mesoporous carbon hollow sphere (MCHS) catalysts were prepared by the one-pot Stöber method using SiO2 as a hard template and resorcinol–formaldehyde (RF) resin as a carbon source, and they were tested for in situ aqueous phase hydrodeoxygenation of methyl palmitate to hydrocarbons using methanol as a hydrogen donor. The formation of the catalyst precursors involves nucleation, growth and co-assembly of RF and SiO2. The introduction of SiO2 can facilitate the construction of the mesoporous and hollow structure and improve the specific surface area. It also reduces the micropore volume due to the reduced graphitization degree of the catalysts induced by SiO2. Thus, the internal diffusion resistance is decreased. Particularly, the Ni–Co alloy particles formed during carbonization are embedded in the mesoporous carbon layer, effectively hindering their sintering and leaching under the harsh hydrothermal conditions. Moreover, the metal sites can be exposed on both mesoporous channels and inner/outer surfaces of the carbon hollow spheres, making the reactants easily accessible. In the in situ hydrodeoxygenation of methyl palmitate, the as-prepared catalyst gives the pentadecane yield of 89.0% at 310 °C for 1 hour. It is noted that the facile diffusion in MCHSs suppresses the undesired C–C bond hydrogenolysis. The catalyst is not obviously deactivated during five reaction cycles. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have attracted significant attention due to their unique electronic structure and extraordinary catalytic reaction activity. In this work, single-atom Au1/TiO2 catalysts were successfully prepared using cold plasma. Notably, plasma-treated TiO2 introduces a substantial number of oxygen vacancies, which played a confinement effect on gold atoms. Au1/TiO2 achieved a remarkable 67% degradation of RhB in just 120 minutes, surpassing the performance of AuNPs/TiO2 by 2.8 times. The high catalytic activity can be attributed to several factors. Firstly, plasma-treated TiO2 contained a higher density of oxygen vacancies and exhibited a narrower band gap, which improved light absorption and facilitated the anchoring of monoatomic Au on the catalyst surface. Additionally, the single-atom Au species exhibited stronger interactions with TiO2, enhancing light absorption and charge transfer capability. Simultaneously, the presence of SACs on the catalyst surface increased the number of active sites, promoting efficient separation of electron–hole pairs and consequently enhancing the photocatalytic degradation activity. Cold plasma technology offers a simple and environmentally friendly platform for the fabrication of SACs, opening up exciting possibilities for catalytic applications. [ABSTRACT FROM AUTHOR]

The quantitative structure-property relationship (QSPR) of constrained geometry catalysts (CGCs) has been analyzed by combining density functional theory (DFT) and multivariate linear regression (MLR). QSPR models for determining the reaction energy barriers of ethylene and 1-octene and molecular descriptors were established and validated with a testing set. At the initiation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.90 and 0.82, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.82 and 0.69. Using the generated QSPR models, the electronic effect was proven to be more critical for determining the energy barriers of ethylene and 1-octene insertion processes. At the propagation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.97 and 0.96, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.93. Particularly, the impact of the steric effect on the energy barriers of ethylene and 1-octene insertion is more pronounced. Furthermore, the correlation between the corresponding energy barriers and experimental activities with three series of CGCs was discussed, which revealed that theoretical calculations are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

The hydrogenation of acetic acid-derived cyclohexyl acetate (CHA) is becoming a safe, efficient and promising route for the production of cyclohexanol (CHOL), an important chemical to produce e-caprolactam. In this work, Cu-Zr catalysts were prepared via different methods for the hydrogenation of CHA. The results showed that a Cu3Zr7-SG catalyst prepared by the sol-gel (SG) method was superior to Cu3Zr7-CP and Cu3Zr7-IM catalysts prepared by the coprecipitation (CP) and impregnation (IM) method, respectively. The Cu3Zr7-SG catalyst showed 97.4% CHA conversion and 95.5% selectivity to CHOL along with 96.3% selectivity to ethanol at 250 1C under 3 MPa of H2. Moreover, the Cu3Zr7-SG catalyst showed a mass specific activity of up to 29.8 gCHA gCu-1 h-1, higher than other Cu-based catalysts under similar conditions. Based on detailed characterization studies, it was found that the larger weak acid sites, more weak and moderate basic sites, higher Cu+/(Cu0 + Cu+) and oxygen vacancies on the surface of the Cu3Zr7-SG catalyst were beneficial for the hydrogenation of CHA. [ABSTRACT FROM AUTHOR]

A new copper(II) bromide/N-methylmorpholine N-oxide (NMO)-promoted method for α-amination of esters under continuous-flow conditions, with reduced catalyst loading is reported. The α-amino esters are precursors for the synthesis of α-amino acids. This method provides α-amino esters in 58-83% yields. The desired Cu(II)Br catalyst is regenerated by in situ oxidation of Cu(I)Br in the presence of NMO. [ABSTRACT FROM AUTHOR]

The availability of catalytic sites for contact with reactants is a key issue to improve the performance of a catalyst, where constructing hollow structured nanomaterials has been considered as an effective strategy. Here, an N-doped carbon supported Ru catalyst with an interior cavity was synthesized by etching a MOF-derived core–shell precursor, in which metal Ru can be highly dispersed in the porous shell. This catalyst shows 98.7% conversion and >99% selectivity towards p-chloroaniline in the hydrogenation of p-chloronitrobenzene, which is better than the corresponding supported catalyst. Moreover, it also displays excellent stability with 5 cycle runs and good substrate universality for the hydrogenation of extensive substituted nitroarenes. Various characterization techniques and control experiments reveal the advantage of the unique structure to promote the mass transport and adsorption of reactant molecules on Ru sites. This work provides a novel strategy to design an efficient Ru-based catalyst for chemoselective hydrogenation. [ABSTRACT FROM AUTHOR]

Three mononuclear Ge(IV) compounds, [(C6H5)2Ge(C13H8N2O4)] (1), [(C6H5)2Ge(C14H10N2O5)] (2), and [(C6H5)2Ge(C14H11NO3)] (3), have been synthesized by the reaction of pro-ligands H2L1 (C13H10N2O4), H2L2 (C14H12N2O5), and H2L3 (C14H13NO3) with (C6H5)2GeCl2 in the presence of triethylamine. All compounds were characterized by FT-IR spectroscopy and NMR spectroscopy. Single crystal X-ray diffraction analysis shows that the germanium(IV) atom exhibits a five-coordinated geometry in compounds 1 and 2. All compounds were screened as Lewis acid catalysts in the [3 + 2] cycloaddition reaction between sodium azide and various nitriles. The reactions resulted in the formation of 5-substituted 1H-tetrazoles with yields of up to 96%. Based on the experimental findings and DFT calculations, a plausible mechanism is proposed for the [3 + 2] cycloaddition reaction. [ABSTRACT FROM AUTHOR]

A set of mononuclear cobalt(III) octahedral complexes {[Co(LH)(acac)] (Co-1H), [Co(LBr)(acac)] (Co-1Br), and [Co(LNO2)(acac)] (Co-1NO2)} were synthesized using new-generation N/O donors, maleonitrile-tethered, tetradentate heteroscorpionate half-reduced Schiff base ligands, 2-((E)-2-hydroxybenzylideneamino)-3-(pyridin-2-ylmethylamino)maleonitrile (H2LH), 2-((E)-(5-bromo-2-hydroxybenzylidene)amino)-3-((pyridin-2-ylmethyl)amino)maleonitrile (H2LBr), and 2-((E)-2-hydroxy-5-nitrobenzylideneamino)-3-(pyridin-2-ylmethylamino)maleonitrile (H2LNO2). All the compounds were well characterized spectroscopically and structurally. The non-covalent interactions present in the lattice of Co-complexes were studied in detail to explain the molecular architecture using the Hirshfeld surface (HS) analysis. The catalytic activity of CO2 fixation towards epoxides under mild and solvent-free conditions was demonstrated. The synthesized complexes are catalysts that are well-active towards the CO2 activation under ambient conditions, whereas most of the reported catalysts require harsh conditions. [ABSTRACT FROM AUTHOR]

Improving the dispersion of metal nanoparticles and suppressing metal aggregation have long been the keys to constructing efficient metal-loaded catalysts. Herein, catalysts of cobalt (Co) supported on nitrogen (N)-doped carbon were prepared by a simple hydrothermal method using folic acid (FA) as the carbon source. Surprisingly, hydrazine hydrate not only facilitated the loading of metal Co, but also regulated the morphology of the catalyst, promoted the uniform distribution of metal Co, and effectively improved the catalytic hydrogenation activity of the catalyst. It was found that the catalyst mediated with 10 mL hydrazine hydrate and pyrolyzed at 900 °C exhibited the best catalytic performance (99.6% conversion of quinoline and 98.0% selectivity for 1,2,3,4-tetrahydroquinoline). In addition, it exhibited satisfying adaptability for diverse substrates. This study can provide great theoretical significance and practical guidance for the preparation of Co–N–C catalysts. [ABSTRACT FROM AUTHOR]

Designing composite catalysts that harness the strengths of individual components while mitigating their limitations is a fascinating yet challenging task in catalyst engineering. In this study, we aimed to enhance the catalytic performance by anchoring ZIF-67 nanoparticles of precise sizes onto lamella Si-MWW zeolite surfaces through a stepwise regrowth process. Co ions were initially grafted onto the zeolite surface using ultrasonication, followed by a seed-assisted secondary growth method. Si-MWW proved to be the ideal zeolite support due to its thin layered structure, large external surface area and substantial lateral dimensions. The abundant Si–OH groups on its surface played a crucial role in securely binding Co ions, limiting size growth and preventing undesirable ZIF-67 aggregation. The resulting ZIF-67/MWW composite with finely dispersed nano-scale ZIF-67 particles exhibited a remarkable catalytic performance and stability in the aldol condensation reactions involving acetone and various aldehydes. This approach holds promise for designing MOF/zeolite composite catalysts. [ABSTRACT FROM AUTHOR]

The nucleophilic ring opening of epoxides by carboxylic acids is an indispensable transformation for materials science and coating technologies. Due to this industrial significance, improvements in operational energy consumption and catalyst sustainability are highly desirable for this transformation. Herein, an efficient, environmentally benign and non-toxic halide free cooperative catalyst system based on an iron(III) benzoate complex and guanidinium carbonate is reported. The novel catalyst system shows improved activity over onium halide catalysts under neat conditions and in several solvents, including anisole and nBuOAc. Detailed mechanistic studies using FeCl3/DMAP as a catalyst revealed the importance of a carboxylate bridged cationic trinuclear μ3-oxo iron cluster and guanidinium carbonate or DMAP as a carboxylate reservoir due to its superior activity. [ABSTRACT FROM AUTHOR]

The biorenewable carbohydrate-derived rigid building block of isosorbide (ISB) has demonstrated potential in high-performance polymer materials; however, a controllable eco-friendly preparation technology is not yet available. For this purpose, a sustainable strategy to synthesize ISB-based polycarbonate (PIC) has been established by adopting the CO2-based compound dimethyl carbonate (DMC) as a monomer and ionic liquids (ILs) as metal-free catalysts. The molecular weight of PICs can be readily controlled by varying the cation structure of IL catalysts. Control experiments, density functional theory (DFT) calculations, and Kamlet–Taft solvent parameters indicated that the H-bond donor/acceptor (HBD/HBA) ability of IL catalysts played a dominant role in regulating catalytic activity. PIC molecular weight can be modulated by modifying the inherent difference in reactivity of endo-OH and exo-OH in ISB, wherein the chain length or substituent group of cations can regulate the HBD/HBA ability of IL catalysts and anions can specifically activate the carbonyl carbon of DMC. The experimental results revealed that a task-specific [Pmim][OAc] catalyst exhibited the highest catalytic activity, which is attributed to its significant role in considerably lowering the disparity in reactivity between endo-OH and exo-OH. For this DMC route, the [Pmim][OAc] catalyst offered a PIC with the highest molecular weight of 57 200 g mol−1 reported to date. Furthermore, a well-supported polymerization mechanism was proposed, in which [Rmim][OAc]'s anion–cation synergistically catalyzed ISB and DMC to prepare PIC. Our findings offer a clear pathway for designing efficient metal-free catalysts to enable the sustainable synthesis of high molecular weight PICs, thus expediting the industrialization of the DMC route. [ABSTRACT FROM AUTHOR]

Carbon dots with good photoelectric properties are usually used as photocatalysts and electrocatalysts, but the good catalytic performance of carbon dots as nanomaterials for thermal catalysis is ignored. Herein, the application of novel efficient catalysts based on carbon dots for the transformation of carbon dioxide (CO2) to carbonates under solvent-free conditions is described. Carbon dots containing carboxyl, hydroxyl, and amine groups were prepared by a microwave technique and employed together with KI, which showed exceptional catalytic activity in the cycloaddition of carbon dioxide with different epoxides. In addition, the catalyst was easily reusable and had stable recyclability. And the catalyst displayed outstanding catalytic performance due to the synergistic effect of carboxyl (–COOH), hydroxyl (–OH), and amine (–NH) groups. [ABSTRACT FROM AUTHOR]

CuO/TiO2 catalysts with varying Sb doping ratios were synthesized and applied in the NH3-SCR process. The results of activity tests revealed that the addition of Sb effectively enhanced the performance of low-temperature SCR. Particularly, the CuSbTiOx-0.2 catalyst exhibited the highest activity, achieving over 91% conversion at 250 °C, along with the highest N2 selectivity and exceptional resistance to SO2. Comprehensive characterization analyses demonstrated that CuSbTiOx-0.2 possessed a significantly large specific surface area, the strongest surface acidity, and superior redox performance among the catalysts studied. In situ DRIFTS experiments provided further insights, indicating that Sb modification generated more active species, thereby enhancing the reactivity of ad-NH3 and ad-NOx species. The SCR reaction mechanism for CuSbTiOx-0.2 predominantly followed the Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms. These findings have the potential to advance the development of novel and effective non-vanadium SCR catalysts. [ABSTRACT FROM AUTHOR]

As important building blocks in natural products and organic synthesis, thioethers have a wide range of potential applications. Herein, polyoxometalate-based ionic liquids (POM-ILs-SO3H) derived from N-alkyl imidazole were synthesized and used for the first time for the thiolation of alcohols to construct C–S bonds in a series of benzyl thioethers. This type of POM-ILs-SO3H catalyst exhibited high catalytic activity, providing up to 98% yield of thioether within 1 h at 70 °C. The alkyl chain length of the imidazole had a certain effect on the solubility of the POM-ILs-SO3H catalysts in the reaction solvent, and then affected their catalytic activity. The catalytic system had a wide substrate scope and was suitable for the reaction of tertiary and secondary benzyl alcohols with thiophenols or cycloalkyl thiols. In particular, [PIMPS]3PW12O40 (PIM = 1-propylimidazole, PS = propane sulfonate) as a reversible phase transformation-type catalyst, combining the advantages of homogeneous and heterogeneous catalysts, exhibited high activity and good recyclability with only a slight decrease in the yield after five runs. Additionally, a carbocation mechanism was proposed for the thiolation reaction of alcohols. [ABSTRACT FROM AUTHOR]

Herein, CoN4, CuN4, and NiN4 complexes with a 14-membered ring hexaazamacrocycle ligand H2HAM were synthesised as precursors for ORR and CO2RR catalysts via a one-pot, gram-scale synthesis procedure, which involved microwave heating for only 10 min. Detailed structures of the obtained 14MR-MN4 complex were revealed by single-crystal X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

In order to reduce the high polarization caused by the hysteresis effect of O2 diffusion and boost the power density of oxygen cathodes under a transient heavy load, an Al-MOF-derived porous carbon-modified Pt/C catalyst is proposed as a new capacitive ORR catalyst to construct super fuel cells (SFCs) via an ORR + EDLC dual-discharge parallel process. Herein, a capacitive porous carbon material (BTCC-2) with a large specific surface area (SSA) and high graphitization was synthesized via one-step carbonization of Al-MOFs (Al-BTC). After compounding BTCC-2 with commercial Pt/C catalysts, electrochemical tests were performed and revealed that the composite with 40% BTCC-2 provided the highest transient discharge performance. Moreover, the composite had a higher onset potential and limiting current density (5.236 mA cm−2) than Pt/C and a half-wave potential (0.833 V) comparable to that of Pt/C. The abundant pore structure and large surface of BTCC-2 greatly increased the interaction between oxygen and the catalyst surface. Besides, the contained BTCC-2 serve as a significant power bank to remarkably buffer and relieve the rapidly decreasing output voltage under an instant heavy load owing to the oxygen deficiencies in a Zn–air battery through the ORR + EDLC dual-parallel-discharge process. The proposed SFC design has potential as a universal method to solve the sluggish ORR process and provide high transient power density for fuel cell-driven vehicles. [ABSTRACT FROM AUTHOR]

Developing highly effective cheap metal oxides is of great value for the 5-hydroxymethylfurfural (HMF) aerobic oxidation to 2,5-furandicarboxylic acid (FDCA) under environmentally friendly conditions. Herein, we synthesized a non-precious cobalt–bismuth binary oxide with rich oxygen vacancies by a facile malic-acid-assisted method and then employed it as a superior catalyst for the HMF aerobic oxidation to FDCA in water. Given the characterization results, the accession of Bi2O3 made the (311) facet become the preferential orientation plane for Co3O4 in the cobalt–bismuth binary oxide. Then, the oxygen vacancies from Co3O4 will be increased due to the greater exposure of Co2+ on the dominant exposed (311) facet, which in turn will facilitate the aerobic oxidation of HMF to FDCA. Evaluating the performance of cobalt–bismuth binary oxide in HMF oxidation reactions, an outstandingly high FDCA yield of 98.23% with nearly 100% HMF conversion could be found over CoBi-12 (Co/Bi molar ratio of 12 : 1) under 0.6 MPa O2 pressure and 110 °C in water for 3 h. The findings of this study can contribute to the development of efficient non-precious metal-based catalysts for the aqueous-phase aerobic oxidation of biomass-derived HMF. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of nitriles is a green and efficient method to produce amines. However, it is still difficult to selectively obtain a specific amine. Herein, we report that a SiC supported highly dispersed Ni catalyst shows high performance for the hydrogenation of nitriles to corresponding primary amines without ammonia addition. Further studies reveal that the Ni/SiC catalyst has a high hydrogen spillover capacity; thus, the active H species dissociated on Ni can easily spill over to the SiC surface and react with the nitrile adsorbed and activated on SiC. Besides, the moderate basicity of Ni/SiC is also responsible for the increased selectivity of primary amines. This study provides a new idea and reference for designing selective nitrile hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

A new method for the generation of benzyl radicals from terminal aromatic alkynes has been developed, which allows the direct cross coupling with acrylate derivatives. Our additive-free protocol employs air-stable diamino Mo3S4 cubane-type cluster catalysts in the presence of hydrogen. A sulfur-centered cluster catalysis mechanism for benzyl radical formation is proposed based on catalytic and stoichiometric experiments. The process starts with the cluster hydrogen activation to form a bis(hydrosulfido) [Mo3(μ3-S)(μ-S)(μ-SH)2Cl3(dmen)3]+ intermediate. The reaction of various aromatic terminal alkynes containing different functionalities with a series of acrylates affords the corresponding Giese-type radical addition products. [ABSTRACT FROM AUTHOR]

The wide application of lithium-ion batteries (LIBs) for electric vehicles forebodes a future decommissioning tide of spent LIBs. Therefore, the recycling of spent LIBs has garnered significant attention, primarily due to the scarcity of resources and the detrimental effects of environmental pollution. However, traditional recycling technologies such as pyrometallurgy and hydrometallurgy methods are limited by their high energy consumption, high pollution, and complicated separation processes. Herein, we propose a novel and general approach to convert a series of spent LiNi1−x−yCoxMnyO2 (NCM) cathodes into Ni–Co–Mn hydroxide (NCM-OH) catalysts for the oxygen evolution reaction (OER) using deep eutectic solvents to extract valuable metals, followed by an in situ precipitation process using oxalic acid and a final self-templating process in an alkaline solution. The NCM-OH catalyst obtained from the spent LiNi0.33Co0.33Mn0.33O2 cathode is found to possess a nanoflake-assembled microrod structure with a large surface area (385.8 m2 g−1) and high porosity, which is endowed with abundant active sites and gas channels for the electrocatalytic reaction and mass transfer process. As a result, the NCM-OH catalyst for the oxygen evolution reaction exhibits a low overpotential of 273 mV at a current density of 10 mA cm−2 with a Tafel slope of 50.46 mV dec−1 as well as satisfactory stability. The effect of the composition on the catalytic performance is also evaluated by comparing different Ni1−x−yCoxMny hydroxide catalysts derived from commercially prevailing spent cathodes. This work provides a promising strategy for recycling spent LIBs into electrocatalyst materials for the OER. [ABSTRACT FROM AUTHOR]

To replace the noble metals used in hydrodeoxygenation (HDO) catalysts, guaiacol HDO was conducted using various transition metal-loaded catalysts. Co/TiO2 was highly active for guaiacol HDO, enabling a more economic removal of the methoxy groups compared to the Ru/TiO2 catalyst, resulting in superior cyclohexanol selectivity. When a WO3 promoter was added to the Co catalyst to enhance its oxygen removal ability, the conversion of guaiacol was severely reduced because the co-impregnated WOx species decreased the number of exposed Co sites. To avoid this phenomenon, Co and WO3 were isolated by physically mixing Co/TiO2 and WO3/TiO2, where 100% conversion and oxygen removal could be achieved under 10 bar H2 at 250 °C. The cause of the catalyst deactivation was systematically investigated by magnetic separation of the physical mixture of the catalysts after the reaction, followed by a series of characterization studies. Temperature-programmed-oxidation mass spectroscopy and Raman spectroscopy revealed that the deposition of carbonaceous species was the main contributor to the deactivation of WO3/TiO2, and the catalytic activity could be successfully recovered by simple calcination at 400 °C. This study provides insights into the development of economical and efficient physically mixed HDO catalysts using transition metals, and contributes to the understanding of the deactivation and regeneration of physically mixed HDO catalysts. [ABSTRACT FROM AUTHOR]

In this study, we aimed to produce isoprene, a diolefin, from a mono-olefin produced by the dehydrogenation of isopentane (iso-C5). Specifically, we attempted to isomerise 2-methyl-2-butene (2M2B), a C5 mono-olefin, followed by dehydrogenation to produce isoprene. The reaction characteristics of the Fe/SiO2 catalysts were investigated in detail. In the presence of hydrogen sulphide (H2S), 2M2B was converted to 2-methyl-1-butene (2M1B) and the target product, isoprene. However, in the absence of H2S, only the isomerisation reaction proceeded, producing 2M1B; isoprene was not produced. Notably, the isoprene yield remained almost unchanged when the concentration of H2S decreased. Furthermore, when isoprene was produced by mixing iso-C5 and mono-olefins (2M2B and 2M1B), the amount of isoprene produced was significantly higher than that from iso-C5 alone. These results indicate that our synthetic strategy is promising for isoprene production. [ABSTRACT FROM AUTHOR]

The practical application of CO2 electroreduction to CO driven by renewable electricity should simultaneously meet the requirements of low overpotential, high CO faradaic efficiency (FE), and low cost. Herein, a new strategy is reported to construct a porous nanoflower Ni–Al NC catalyst with excellent catalytic activity via p–d orbital hybridization of Al and Ni. The optimized Ni–Al NC catalyst exhibits an outstanding CO2 electroreduction activity with the maximum CO FE of 98%, low onset potential of −0.5 V vs. RHE, and wide FECO plateau (>90% from −0.7 to −1.0 V vs. RHE), showing great promise for practical applications. The experimental results showed that the p–d hybrid Ni–Al NC catalyst not only enriched its reaction sites but also withstood potential changes in the highly selective reduction of CO2 to CO. This study provides a catalyst design strategy for the efficient electrocatalytic reduction of CO2 to CO under varying potentials. [ABSTRACT FROM AUTHOR]

In this study, 13-Ni/ZrO2, 13-Ni3P/ZrO2, 13-Ni/SiO2, and 13-Ni3P/SiO2 catalysts were used in the hydrogenation of diethyl oxalate (DEO) to ethyl glycolate (Egly) to investigate the modulating effect of phosphorus. XRD, TEM, and FT-IR spectroscopy results indicated that phosphorus acts as a distributor of Ni metallic particles and thereby shows a segregation effect. The presence of P transformed the linkage of surface metals from an original Ni–Ni–Ni–Ni– to a P–Ni–P–Ni–P state, and FT-IR spectra showed that the former adsorbed CO in a combination of linear and bridging adsorption modes, whereas the latter predominantly in CO linear adsorption. Bridging adsorption occurs via dual sites and makes preliminary hydrogenation products less likely to detach from the catalyst surface, thus facilitating deep hydrogenation, while linear adsorption facilitates partial hydrogenation via rapid detachment of intermediate products such as Egly. Different loadings of Ni3P/SiO2 catalysts show incomplete phosphorylation with an increase in nickel loading, giving rise to a state of coexistence of Ni and Ni3P crystalline phases. This may lead to a coexistence of surface Ni–Ni–Ni–Ni and P–Ni–P–Ni–P and an increase in the corresponding bridging adsorption/linear adsorption ratios, making deep hydrogenation occur partially besides stepwise hydrogenation. [ABSTRACT FROM AUTHOR]

Methanol steam reforming is considered as a potential hydrogen supply pathway, and Cu-based catalysts are commonly used catalysts for this reaction. A series of CZAT-x catalysts were synthesized, which are derived from Cu/ZnO/Al2O3 catalysts by modifying the method of introducing TiO2 in this study. Characterization techniques (BET, XRF, XRD, H2-TPR, N2O chemisorption, TEM, and XPS) revealed that the mode of TiO2 introduction primarily influences surface Cu dispersion, reducibility and Cu–Ti interaction, subsequently affecting CZAT-x catalysts' catalytic activity and thermal stability in methanol steam reforming. The TiO2-doped catalyst prepared through solvent-assisted ball milling demonstrated the highest activity. The complete conversion of methanol could be achieved under the conditions of a water-to-methanol ratio of 1.2 and a reaction temperature of 493 K, and the H2 time-space yield could reach 103.9 mol kg−1 h−1. Furthermore, even after 10 h of thermal treatment test at 723 K, the CZAT-EA catalyst maintained a high methanol conversion rate. [ABSTRACT FROM AUTHOR]

Nickel catalysts were synthesized for solid-state NaBH4 composites by reducing nickel chloride with sodium borohydride. The effect of heat treatment on their magnetic properties and the hydrogen generation rate was studied. It has been established that calcination of nickel catalysts to 350 °C has a negligible effect on the rate of gas generation but provides fast separation of more than 70% of the catalyst from the spent reaction medium using a magnet. According to XRD data (in situ) and the found Curie point value (358 °C), the enhancement of magnetic properties results from the accumulation of the ferromagnetic phase of the reduced Ni0 metal. A further increase in the heat treatment temperature (≥400 °C) decreases the activity of nickel catalysts, accompanied by a decrease in the specific surface area of the samples, by the complete conversion of cobalt boride Ni3B into the metallic form Ni0 and by the formation of the boron oxide shell around the nickel particles. To increase the activity of the nickel catalyst calcined at 350 °C, cobalt was deposited using incipient wetness impregnation, followed by reduction with sodium borohydride. The proposed technique allowed us to uniformly anchor cobalt on the surface of nickel particles, which ensured an increase in the gas generation rate. Thus, an effective ferromagnetic cobalt–nickel catalyst has been proposed for solid-state hydrogen-generating materials based on sodium borohydride. Note that the removal extent of this catalyst from the spent solution was about 85%. [ABSTRACT FROM AUTHOR]

Maintaining the stability of noble metals is the key to the long-term stability of supported catalysts. In response to the instability of noble metal species at high temperatures, we developed a synergistic strategy of dual oxide supports. By designing and constructing ceria components with small sizes, we have achieved unity in the ability of catalytic materials to supply oxygen and stabilize metal species. In this study, we prepared Al2O3-CeO2-Pd (AlCePd) catalysts containing trace amounts of Ce through the hydrolysis of cerium acetate, which achieved 100% CO conversion at 160 °C. More importantly, the activity remained at its initial 100% in the long-term durability testing, demonstrating the high stability of AlCePd. In contrast, the CO conversion of the CeO2-Pd (CePd) catalyst decreased from 100% to 54% within 3 h. Through comprehensive studies, we found that this excellent catalytic performance stems from the stabilizing effect of an alumina support and the possible reverse oxygen spillover effect of small-sized ceria components, where small-sized ceria components provide active oxygen for independent Pd species, making it possible for the CO adsorbed on Pd to react with this oxygen species. [ABSTRACT FROM AUTHOR]