Bifunctional Catalysts Research Articles

Hydrocracking of n-Hexadecane and Diesel Fuels over Bifunctional Catalysts based on High-Crystallinity Granulated Hierarchical ZSM-5 Zeolites

Hydrocracking of n-Hexadecane and Diesel Fuels over Bifunctional Catalysts based on High-Crystallinity Granulated Hierarchical ZSM-5 Zeolites

Integration of Fe3C and Fe3P Nanoparticles Anchored on N-Doped Carbon as Bifunctional Oxygen Catalysts for Rechargeable Zn-Air Batteries

Integration of Fe₃C and Fe₃P Nanoparticles Anchored on N-Doped Carbon as Bifunctional Oxygen Catalysts for Rechargeable Zn-Air Batteries

Preparation and Characterization of Sulfonated CaO Catalyst for Biodiesel Production from Waste Cooking Oil

Biodiesel production depends on raw materials. Low-quality oils, such as cooking oil, crude palm oil, and sludge oil, are used to reduce costs, and they contain free fatty acids (FFA) and water. Soap can be produced when using the alkaline catalyst during transesterification. In this work, the sulfonation method prepared the esterification of waste cooking oil by sulfonated CaO as a bifunctional catalyst. The sulfonated CaO catalysts were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), temperature-programmed desorption of carbon dioxide and ammonia (TPD), BET surface area, and scanning electron microscopy (SEM). It was observed that the specific surface area, pore volume, and pore diameter of the CaO increased after being sulfonated with a 2 M sulfuric acid solution. It showed a high total surface acidity and basicity, 7.22 and 3.86 mmol/g, respectively. The optimal FFA conversion (84.94 %) from the waste cooking oil was acquired at a reaction temperature of 65 ˚C, a 9:1 MeOH: Oil molar ratio, and 5 wt% catalyst loading for a 3 h reaction time. The 2 M sulfonated CaO catalyst can be reused twice with a high FFA conversion without further treatment under optimized reaction conditions. The 2 M sulfonated CaO catalyst has potential treatment for biodiesel production from high-FFA oils due to its lower production cost and high catalytic activity.

N-Doped Carbon-Incorporated Cobalt-Iron Mixed-Metal Phosphide Nanoboxes as Efficient Bifunctional Catalysts for Overall Water Splitting.

Optimizing the composition and structure of nanocatalysts is an efficient approach to achieving the top electrocatalytic performance. However, the construction of hollow nanocomposites composed of metal phosphides and highly conductive carbon to promote the electrocatalytic performance of metal phosphide-based catalysts is rarely reported. Herein, a CoFeP/C nanobox nanocomposite consisting of Co-Fe mixed-metal phosphides and N-doped carbon was successfully fabricated through an ion-exchange phosphidation strategy derived from ZIF-67 nanocubes. Benefiting from the synergistic effects between multiple components and the unique hollow structure, CoFeP/C nanoboxes can catalyze the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with high activity and stability. Furthermore, in the construction of an alkaline water electrolyzer using CoFeP/C nanoboxes as both OER and HER catalysts, they were capable of efficiently splitting water with a current density of 10 mA cm-2 achieved by applying only 1.62 V of cell voltage and exhibited outstanding durability. Density functional theory calculations demonstrate that synergistic effects among multiple components in CoFeP/C nanoboxes can lower the hydrogen adsorption free energy of the HER and OER energy barrier of the rate-determining step, thus promoting the catalytic reactions. The design and synthesis of CoFeP/C nanoboxes highlight the importance of the composition and structural characteristics in achieving high-performance water electrolysis.

Bifunctional Catalysts with Separated and Tunable Sites on Zeolites for Relay Catalysis of the Oxidative Dehydrogenation of Propane Using CO2

AbstractThe oxidative dehydrogenation of propane using CO2 (CO2‐ODH) technology has broad application prospects in the production of propylene and the utilization of CO2, and the development of efficient CO2‐ODH catalysts is of great significance. However, it remains a challenge to develop a highly efficient catalyst that can activate both C─H and C═O. Herein, a PtZn/Co@S‐1 catalyst with a very low precious metal content of 0.2 wt.% is reported. Benefiting from the PtZn4 nanoclusters dispersed on the surface of Silicalite‐1 zeolite and tetrahedrally coordinated Co2+ in the Silicalite‐1 zeolite framework via relay catalysis, the independent dual sites structure (PtZn/Co@S‐1) greatly promotes CO2‐ODH reaction with a high conversion rate of both C3H8 (59.7%) and CO2 (44.3%), and propylene selectivity of 94.9%, thus upsetting the equilibrium for direct dehydrogenation of propane. Experimental measurements and density functional theory calculations suggest that the PtZn4 and Co2+ interfaces are likely propane dehydrogenation and carbon dioxide hydrogenation active sites respectively.

Synthesis and Application of SAPO-11 Molecular Sieves Prepared from Reaction Gels with Various Templates in the Hydroisomerization of Hexadecane

Among the most selective catalytic systems for the hydroisomerization of C16+ n-paraffins, catalytic systems based on SAPO-11 are quite promising. In order to increase the activity and selectivity of these bifunctional catalysts, it is necessary to reduce the diffusion restrictions for the reacting molecules and their products in the microporous structure of SAPO-11 by reducing the crystal size. To solve this problem, we have studied the influence of different templates (diethylamine, dipropylamine, diisopropylamine, and dibutylamine) on the physicochemical properties of reaction gels and SAPO-11 silicoaluminophosphates during their crystallization. Using XRD, SEM, and NMR techniques, we found that regardless of the template used, the reaction gel after the aging process at 90 °C is an AlPO4·2H2O hydroaluminophosphate. At the same time, the nature of the template affects the morphology and crystal sizes of the intermediate alumophosphate, AlPO4·2H2O, and the molecular sieves, SAPO-11. The acidic properties and the porous structure characteristics of SAPO-11 are also affected by the template. A template was proposed to enable the synthesis of nanoscale SAPO-11 crystals. The influence of the morphology and crystal size of SAPO-11 on the catalytic properties of a bifunctional catalyst based on SAPO-11 in the hydroisomerization of hexadecane was investigated.

Novel Ru‐O3Se4 Single Atoms Regulate the Charge Redistribution at Ni3Se2/FeSe2 Interface for Improved Overall Water Splitting in Alkaline Media

AbstractDeveloping low‐cost, highly active, and stable bifunctional catalysts is of great significance for electrochemical water splitting. Herein, novel Ru‐O3Se4 single atoms doped Ni3Se2/FeSe2 interface catalyst is fabricated by a two‐step method for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Notably, Ru‐Ni3Se2/FeSe2 nanosheets exhibit excellent HER (43 mV@10 mA cm−2) and OER (283 mV@100 mA cm−2) activities in alkaline solution. In particular, the mass activity of Ru‐Ni3Se2/FeSe2 catalyst is 3593.61 mA mg Ru−1 at 200 mV for HER and 7073.80 mA mgRu−1 at 400 mV for OER, which is 25.91 and 367.28 times of commercial Pt/C and RuO2, respectively. In situ spectroscopy techniques confirm Ru‐O3Se4 single atoms facilitate the adsorption of intermediates H* and OOH* during HER and OER processes, respectively. Further density functional theory calculations reveal introducing Ru‐O3Se4 single atoms causes the transfer of electrons from Ru to Ni and Fe atoms, leading to a redistribution of charge at the Ni3Se2/FeSe2 interface, thus reducing the energy barriers of rate‐determining step to −0.37 and 1.92 eV for HER and OER, respectively. This work emphasizes the significant role of single atoms at the interface for overall water splitting.

Integrated in situ spectroscopic characterization of bi-functional nanoporous hybrid catalysts

Bi-functional catalysts possess various catalytic sites and can catalyze different types of reactions in a single-pot cascade manner. Herein, we report the synthesis and characterization of mono- and bifunctional silica-based mesoporous hybrid catalysts involving acid and base active sites. The ability for cooperative catalysis has been investigated using a multi-technique approach involving powder X-ray diffraction, FT-IR, and multinuclear MAS NMR spectroscopy, as well as thermogravimetric analysis. To elucidate the nature and strength of multifunctional catalytic sites, different types of probe molecules were employed and studied using spectroscopic techniques. The results show that the activity of the mesoporous surface-grafted acid and/or base sites is directly related to the intimacy criterion, the separation between the different types of catalytic sites. The presence or absence of mutual interactions between the different catalytic sites dictates the selectivity and yield of the reactions.

Highly selective production of 2-methylnaphthalene by CO2 hydrogenation and naphthalene alkylation

Many researchers have extensively studied the alkylation of naphthalene with methanol for the preparation of high-value-added chemicals, especially methylnaphthalenes (MNs). Studies indicated that methanol generates a large number of methanol-to-olefin by-products on zeolites, resulting in low selectivity of the target product and poor stability of the catalyst, limiting its application in the industrial field. In this study, CO2 hydrogenation was coupled with naphthalene alkylation, and the H3CO* active intermediate generated in situ was alkylated with naphthalene by using metal oxide-zeolite (OX-ZEO) bifunctional catalysts, which exhibited the ‘slow release’ phenomenon of the methylation reagent. It improved naphthalene conversion, suppressed deep alkylation and coke deposition side reactions and kept the catalyst stable for up to 500 h. A high-density and medium-strength Brønsted acid center facilitated the efficient migration of H3CO* active intermediates with the desorption of 2-methylnaphthalene (2-MN), which was particularly important for improving naphthalene conversion and 2-MN selectivity. The in situ IR showed that more Brønsted acid sites of Ga-S-1 effectively pulled the migration process of H3CO* species to the zeolitic acid center and increased the efficiency of C-C coupling compared to ZSM-5, which promoted the alkylation of H3CO* species with naphthalene. The results of chemisorption experiments showed that the medium-strength Brønsted acid site, which promoted the desorption of 2-MN, inhibited the deep alkylation reaction. The 2,6-dTBPy-IR results showed that the presence of fewer Brønsted centers on the outer surface of Ga-S-1 further optimized the product distribution and enhanced the selectivity of 2-MN in MNs to more than 90 %. Under optimal conditions, 80.1 % selectivity for MNs was obtained via ZnZrOx&Ga-S-1 bifunctional catalysts, with 97.4 % selectivity for 2-MN in MNs.

Surfactant-modified ZnFe2O4/CaOPS porous acid-base bifunctional catalysts for biodiesel production from waste cooking oil and process optimization

Biodiesel production from waste cooking oil (WCO) with high acid value is useful for clean energy development and utilization. In this work, ZnFe2O4(5)/CaOPS porous bifunctional catalysts were prepared for catalytic production of biodiesel with the help of surfactants such as PVP, SDS and citric acid, using a sol-gel method. The ZnFe2O4(5)/CaOPS catalysts were characterized using XRD, SEM, EDX, NH3-TPD, and BET. The parameters (reaction temperature, catalyst dosage, methanol-oil ratio and reaction time) for the transesterification reaction to produce fatty acid methyl esters (FAMEs) were optimized for the optimal materials using a one-variable method. Experiments were designed using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) for global optimization to obtain the best process parameters. The final average yield of FAMEs was 96.89% under the optimum reaction parameter of catalyst dosage of 5.06wt%, reaction temperature of 63.69°C, reaction time of 212.22min and methanol-oil ratio of 12.96:1. The prepared biodiesel was characterized using FT-IR, 1H NMR as well as 13C NMR and compared with international standard ASTM D6751. The ZnFe2O4(5)/CaOPS catalyst has excellent stability in biodiesel production and has some free fatty acid tolerance. In addition, a cost analysis and sensitivity analysis were done for the production of WCO biodiesel. It is hoped that the research results in this paper can provide a theoretical basis for biodiesel production from WCO with high free fatty acid content.

Direct synthesis of liquid hydrocarbons from CO2 and H2 over bifunctional ZnCrOx-НZSM-5 combined and composite catalysts in a single reactor

A one-stage synthesis of gasoline fraction from CO2 and H2 was carried out on Zn-Cr–oxide-zeolite combined and composite catalysts. It was found that after oxidative and reduction treatment the catalysts contain ZnO and ZnCr2O4 phases. The one-step coprecipitation of zinc and chromium salts in the presence of zeolite allows obtaining an active bifunctional composite catalyst, each particle of which contains Zn-Cr oxide and zeolite components. A synergistic catalysis due to a closer distance of metal and acid sites increased the efficiency of such a catalyst in CO2 hydrogenation. It was found that the optimal temperature of oxidative activation of the composite catalyst is 400 ° C. With an increase in the temperature of oxidative treatment of the composite catalyst from 400 to 500°C, part of the zinc leaves the structure of the non-stoichiometric spinel and leads to a decrease in the basicity of the catalyst, which is responsible for the activation of CO2 on surface oxygen vacancies. Agglomerated ZnO particles blocked the pores and reduced their volume, as well as the specific surface of the catalyst. At the same time, the total acidity of the catalyst decreased. ZnO-species, which have hydrogenating activity, under the reaction conditions removed alkenes from the reaction cycle and thereby reduced the C5+–selectivity of the composite catalyst. Among the studied catalysts, the ZnCrOx-НZSM-5/Al2O3(400) composite catalyst in the tail-gas recirculation mode at 380°C and 10 MPa demonstrated high CO2 conversion of 25% and high selectivity for C5+–HCs of 53 wt% with a high content of isoalkanes 71 wt% for 60 hours. The methane content in the tail-gas did not exceed 3 vol%. The results obtained will be used to develop approaches to creating effective catalysts for the one-stage CO2 hydrogenation into valuable petrochemical products.

Strengthening heterogeneous strain in FeCoNiMo-based high-entropy alloys for advanced energy conversion

Inducing lattice distortion and applying strain between atoms to regulate the electronic structure is an effective strategy for optimizing catalytic activity; however, several challenges still remain. Herein, heterogeneous strain triggered by large-radius atoms is proposed to effectively optimize the electronic structure and energy level of FeCoNiMo-based HEAs, thereby significantly enhancing alkaline hydrogen evolution and triiodide reduction reaction performance. Following the introduction of large-radius atoms such as Nb, W or Ta into FeCoNiMo-based HEA catalysts, the overpotential at η10 was reduced by more than half (from 172 to 84 mV). Using FeCoNiMoNb/C as the counter electrode in photovoltaic devices, 8.50% PCE was achieved, which is higher than that of FeCoNiMo- and Pt-based photovoltaic devices. This study leverages large-radius atoms to trigger strengthened heterogeneous strain within HEA catalysts, providing an innovative approach to effectively regulate their electronic structures and develop high-performance, low-cost bifunctional HEA catalysts.

Cobalt-modified nitrogen-doped carbon nanotubes as bifunctional catalysts for one-pot synthesis of 2,5-diformylfuran from glucose

Cobalt-modified nitrogen-doped carbon nanotubes as bifunctional catalysts for one-pot synthesis of 2,5-diformylfuran from glucose

Pt-Doped Co3O4 Nanowires as High-Efficiency Cathodic Catalysts for Improved Lithium-Oxygen Batteries and Insights into The Electrochemical Reaction Pathway

Lithium-oxygen batteries (LOBs) have garnered considerable interest as promising energy storage solutions owing to their exceptional theoretical energy density. Nevertheless, their practical implementation is impeded by notable obstacles, involving suboptimal energy efficiency, excessive overpotential and limited cycle life. Tricobalt tetra-oxide (Co3O4) is a promising cathodic bifunctional catalyst for LOBs. With deliberate alien-atom doping, their catalytic performance can even be further improved due to the resulted structural adjustment. In this work, platinum-doped cobalt oxide nanowires have been hydrothermally synthesized on the acid-treated carbon paper substrates. These nanowires, with a thickness of about 150 nm and a length of approximately 1.5 μm, are closely stacked and display an urchin-like morphology. As employed as the cathode for the LOBs, an excellent performance is delivered, including a discharge capacity of 17079.4 mAh g−1, an overpotential of 0.88 V, a cycle stability of over 75 cycles, and an initial coulombic efficiency of 95.71%, which is superior to the batteries based on pure Co3O4 nanowires. Combined with the results of density functional theory (DFT) calculations, it can be deduced from the experimental observation that the nanowires’ adsorption affinity toward the discharge/charge intermediates of lithium superoxide (LiO2), as well as the morphologies and formation/decomposition pathways of the discharge products, are all governed by Pt-doping. The Pt-doping-improved adsorption induces a transition of the discharge products from the solution-pathway grown flake-like morphologies which are randomly stacked in the voids between pure Co3O4 nanowires to the surface-pathway grown film-like morphologies which are tightly wrapped around the Pt-doped Co3O4 nanowires. The close contact between the film-like discharge products and the Pt-doped Co3O4 nanowires is facile for fast oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, hence the lowered overpotential and enlengthened cycle durability of the batteries. Furthermore, the increased amount of the film-like discharge products results in the enhancement of the capacity of the batteries. This work may shed light on approaches for boosting the electrochemical performance of the transition-metal-oxide-based LOBs through the strategy of alien-atom doping.

NiFeS2/NiFe2O4 Composites Constructed by Etching Modified Fe Foam as an Efficient Bifunctional Catalysts for Overall Water Splitting

NiFeS2/NiFe2O4 Composites Constructed by Etching Modified Fe Foam as an Efficient Bifunctional Catalysts for Overall Water Splitting

Effect of porous structure on Ni-CaO bifunctional catalysts for the integrated CO2 capture and methanation process

Integrated CO2 capture and in-situ methanation technology (ICCU-M) is a promising approach for directly capturing and simultaneously converting CO2 into CH4 in a single process. The bifunctional catalyst that combines CO2 adsorption and catalytic properties into one particle is an ideal choice for ICCU-M process. In this work, we demonstrate that pore structure of bifunctional catalysts plays a pivotal role in their ICCU-M performance. The characterization results indicate that the presence of porosity weakens the encapsulation of Ni nanoparticles by the formed CaCO3 layer due to the volume expansion caused by the larger molar volume of CaCO3 compared to CaO (36.1 cm3/mol vs 16.9 cm3/mol). The ICCU-M performance shows that 5Ni-CaO-C1:1 has a lower CH4 formation temperature of 325 °C than 425 °C of 5Ni-CaO-w due to its abundant pores retaining more Ni sites, thus providing higher methanation activity. Meanwhile, 5Ni-CaO-C1:1 also exhibits higher CH4 selectivity than 5Ni-CaO-w (93.5 % vs 40 %) at 525 °C. Our results show that the volume expansion process of bifunctional catalysts has a significant impact on ICCU-M performance, which needs to be considered when designing efficient bifunctional catalysts for ICCU processes.

Hydrodeoxygenation of Lignin Phenol Derivatives to Aromatic Hydrocarbons: A Mini-Review of Metal/Acid Bifunctional Catalysts

Hydrodeoxygenation of Lignin Phenol Derivatives to Aromatic Hydrocarbons: A Mini-Review of Metal/Acid Bifunctional Catalysts

Electrochemical upgrading of PET plastic wastes for hydrogen production using porous Fe–Ni2P nanosheets

The electrochemical upgrading of PET plastic wastes-to-hydrogen is an important conversion system for achieving sustainable, low-cost and scalable hydrogen production. Designing cost-effective and highly active dual-function electrocatalysts for the ethylene glycol (PET monomer) oxidation reaction (EGOR) and hydrogen evolution reaction (HER) is very crucial for achieving practical application of PET plastic wastes upgrading assisted electrochemical water splitting technology. Herein, a simple hydrothermal-phosphating two-step method is implemented to achieve ultrathin porous iron (Fe) doped nickel phosphide (Ni2P) nanosheets attached to the nickel foam (named as Fe–Ni2P/NF). Profiting from the ample active sites provided by the ultrathin structure, porous structure and the optimized electronic structure caused by Fe doping, Fe–Ni2P/NF exhibits predominant electroactivity for HER and EGOR. Additionally, PET plastic wastes hydrolysate electrolyzer is assembled by using Fe–Ni2P/NF as a dual-functional electrode for the co-generation of hydrogen and formate. The constructed Fe–Ni2P/NF||Fe–Ni2P/NF electrolyzer only requires an electrolysis potential of 1.39 V to derive 10 mA cm−2 current density, which is lower than that of conventional water splitting (1.55 V). This work would afford a reference for constructing cost-efficient and steady plastic-assisted water electrolysis bifunctional catalysts, and expands the field of energy-saving co-generation of value-added chemicals and hydrogen.

Transition metal ions-chelated COFs derived bifunctional oxygen catalysts for rechargeable Zn-air batteries

Improving energy conversion efficiency and battery cycle stability is an essential goal in energy conversion and storage, while a critical factor in achieving this goal is the design of effective bifunctional catalysts. The covalent organic framework is a new type of high molecular material that can be employed as an ideal template for quantitative chelate metal ions to synthesize highly efficient bifunctional catalysts with high dispersion metal active sites. In this work, the Fe2Ni1/NiFe2O4@NCG bifunctional catalysts are constructed by employing metal-chelated COFs and MA/GO mixture as primary precursors combined with a high-temperature pyrolysis strategy. COFs and MA serve as chelators and spacers to improve the dispersion of metal nanoparticles. The Fe2Ni1/NiFe2O4@NCG composite exhibits a large BET surface area and hierarchical structure with plentiful nanoparticles on the carbon layers. HRTEM proves the coexistence of FeNi and NiFe2O4. The optimal Fe2Ni1/NiFe2O4@NCG-800 composite shows satisfactory catalytic O2 performance, providing a half-wave potential of 0.857 V for ORR and an overpotential of 244 mV for OER. Meanwhile, DFT calculations prove that electron redistribution occurs at the interface between FeNi and NiFe2O4 after combination. The Fe2Ni1/NiFe2O4@NCG-based liquid and solid-state ZABs perform very well, exhibiting large specific capacities (796 mAh·g−1 for aqueous ZAB; 742 mAh·g−1 for solid-state ZAB) and stable charge-discharge cycle performance (300 h for aqueous ZAB; 180 h for solid-state ZAB).

The application of S, N co-doped biomass carbon-based FeCoNi bifunctional electrocatalysis in zinc-air battery

The development of efficient Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts from biomass is of significant importance for the commercial application of zinc-air batteries (ZABs). Herein, a bifunctional catalyst (FeCoNi@SNC) is successfully synthesized through introducing Fe, Co and Ni atoms, fish scale-derived carbon (CFS) as the precursor, thiourea and dicyandiamide (DCDA) as the S and N sources, respectively. More importantly, FeCoNi@SNC is identified as a composite material containing FeCo, FeNi3 and metal sulfides. A large number of fluffy carbon nanotubes are induced to grow on the CFS surface by metal nanoparticles, while M-N, M-O and M-S are formed. The catalytic performance is positively influenced by the unique morphology and different active sites of FeCoNi@SNC. To our delight, FeCoNi@SNC exhibits excellent catalytic activity in both ORR (E1/2=0.85 V) and OER (Ej=10= 1.556 V). As a cathode in zinc-air batteries, FeCoNi@SNC possesses significant potential with a peak power density of 146.9 mW cm−2, a specific capacity of 706.9 mAh g−1, and an open circuit voltage of 1.525 V. A novel approach is provided by this work for designing biomass-derived ORR/OER bifunctional catalysts and their application in zinc-air batteries.