Hierarchical Hollow Structure Research Articles

Simultaneously high mass-loading and volumetric energy density in Ag2O-intercalated MnO2-based supercapacitor with rapid electron/ion transport channels

High volumetric energy density (VED) is essential for supercapacitors’ practicality, but is extremely challengeable when high mass-loading is simultaneously demanded, because the high mass-loaded electrode always encounters the limited ions-diffusion accessibility and sluggish electron transferability. Herein, for the first time, Ag2O-intercalated hollow MnO2 (Ag2O-HMnO2) electrode with rapid ion/electron transport channels is rationally designed and fabricated by a facile in-suit growth & self-sacrificing template method. Ultrahigh mass-loading benefits from the randomly arrayed MnO2-nanosheets fully covered on silver-nanowire@polypyrrole (AgNW@PPy-template). Vast interior space in MnO2, which forms after the oxidative decomposition of AgNW@PPy-template, offers large electrode–electrolyte interfaces and huge open space channel for unimpeded ions transport. Such Ag2O-intercalated hierarchical hollow structure not only provides spacious “ion transport channel” (hollow interior space) and “reservoir” (much space between neighboring MnO2-nanosheets) for ions diffusion/storage, but also boosts electron transferability via the conductive Ag2O-particulate-based percolation networks. As a consequence, Ag2O-HMnO2 exhibits excellent electrochemistry performance and unprecedented MnO2 utilization efficiency. Ag2O-HMnO2-based supercapacitor exhibits a remarkably enhanced VED of 7.33 mWh cm−3, approximately sixfold improvement compared to that of pristine MnO2. The novel structure engineering strategy presented herein facilitates the excellent ion/electron transferability, which may open a new avenue for transition-metal-oxide/hydroxides-based supercapacitors to achieve high mass-loading and VED.

Ru-embedded 3D g-C3N4 hollow nanosheets (3D CNHNS) with proficient charge transfer for stimulating photocatalytic H2 production

In the recent development of structured materials, efficient and low-cost materials are highly demanding for hydrogen production. In this work, novel 3D graphitic carbon nitride hollow nanosheets (CNHNS) with controlled morphology loaded with Ru for photocatalytic hydrogen production has been investigated. Compared to CN, CNHNS improves H2 evolution of 2 times due to hollow structure with higher light absorption and proficient separation of charges within 3D structure. The highest H2 evolution was attained over 3% Ru loaded CNHNS with yield rate of 1580 μmol g−1 h−1, which was 11.9 times higher than it was evolved over CNHNS and 15.1 times more than using CN, respectively. This obvious augmented photoactivity can be assigned to boosted charges separation in hollow structure, whereas, Ru further promoted the transfer of electrons. The performance of 3D Ru/CNHNS was further increased in an externally reflected solar system, which was 1.30 times more than using photoreactor without reflector. This was evidently due to increasing light intensity inside the reactor by reflecting light, thus, promoting quantum efficiency under the same source of light. The stability results further confirm continuous H2 evolution even after six cycles. Thus, newly developed method for synthesis of hierarchical 3D hollow structures and externally reflector solar photoreactor will provide new directions for hydrogen production systems.

Hierarchically urchin-like hollow NiCo2S4 prepared by a facile template-free method for high-performance supercapacitors

Hollow structures draw much attention for high energy density supercapacitors due to their large hollow cavities, high specific surface area, and low interfacial contact resistance. However, constructing hierarchical hollow structures remains a challenge. Herein, we reported a facile template-free method for a novel urchin-like hollow nickel cobalt sulfide (NiCo2S4). The hollow interior and urchin exterior remarkably improved the specific capacitance and accommodated structural collapse caused by electrochemical reactions. Owing to these features, the urchin-like hollow NiCo2S4 spheres exhibited an impressive capacitance of 1398F g−1 at 1 A g−1 and maintained 1110F g−1 with a large current density of 10 A g−1. The hybrid supercapacitor fabricated by NiCo2S4 and active carbon possesses an energy density of 39.3 Wh kg−1 at a power density of 749.6 W kg−1 and an outstanding cycling stability of 74.4% retention after 5000 cycles. Our work presents a facile method of constructing a hollow structure of binary sulfide materials and also makes progress on highly efficient supercapacitors.

Hierarchical lichee-like Fe3O4 assemblies and their high heating efficiency in magnetic hyperthermia* *Project supported by the National Natural Science Foundation of China (Grant No. 61975162), Youth Research Foundation of Shanxi Datong University (Grant No. 2019Q1), Important R&D Projects of Shanxi Province, China (Grant No. 201803D121083), and Shanxi Scholarship Council, China (Grant No. 2020-135).

A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia. Two kinds of thermoseed materials: hierarchical hollow and solid lichee-like Fe3O4 assemblies, are synthesized by a facile hydrothermal method. The crystal structure of Fe3O4 assemblies are characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, the prepared Fe3O4 assemblies are used as a magnetic heat treatment agent, and their heating efficiency is investigated. Compared to solid assembly, hollow lichee-like Fe3O4 assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time, which is ascribed to its higher saturation magnetization, larger initial particle size, and the unique hierarchical hollow structure. Furthermore, the magnetothermal effect is primarily attributed to Néel relaxation. Overall, we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.

Enhanced Diffusion Kinetics of Li Ions in Double-Shell Hollow Carbon Fibers.

The rational design and preparation of hierarchical hollow structures have promising potential in electrochemical energy storage systems. In this paper, double-shell hollow carbon fibers (DSHCFs) with tunable thickness and shell spacing are prepared using hollow electrospun polystyrene fibers as the hard template and in situ coated polypyrrole as the carbon source. The as-prepared DSHCFs with an optimized structure exhibit a submicrometer shell spacing and a nanoscaled shell thickness, which guarantees sufficient contact area with the electrolyte and provides abundant electrochemical active sites for Li+ storage. Owing to the unique structural advantages, a DSHCF-based anode shows favorable transport kinetics for both Li+ ions and electrons during the lithiation/delithiation process, and a high reversible capacity of 348 mAh g-1 at 5.0 A g-1 is well maintained even after 500 cycles with no obvious capacity attenuation. Particular emphasis is given to kinetic Li+ storage mechanisms in DSHCFs that are discussed in detail, providing a new avenue for developing high-performance carbon materials for the practical application of energy storage devices.

HCl induced structure evolution and dual-frequency broadband microwave absorption of PANI hierarchical microtubes

High-performance absorbers are in urgent demand for dealing with the increasing electromagnetic wave (EMW) pollution caused by the rapid development of information technology. Herein, we developed a simple SDS/HCl-assisted oxidative polymerization method for the controllable synthesis of nanorod-coated PANI hierarchical microtubes as an efficient EMW absorber. The morphological evolution can be expediently achieved from hierarchical microtubes and solid nanofibers to nanorods by adjusting the HCl concentration. The formation of PANI hierarchical microtubes is caused by the cooperation of SDS and the minimum surface energy. What is more, morphology-dependent conductivity and EMW absorption properties were systematically investigated. Owing to the hierarchical 1D hollow structure and carrier concentration, the ultimate conductivity reached 0.08 S/cm at [HCl] = 7.5 mM. The corresponding HCl-doped PANI hierarchical microtubes exhibited superior EMW absorption properties (EMWAPs) with a large absorption of −43.6 dB and a wide absorption band of 5.84 GHz in relation to a 1.55 mm thick sample. The excellent EMWAPs are the consequence of the high conductivity and distinctive 1D, hierarchical, and hollow structure, which generate enhanced permittivity, multiple resonances, strong attenuation capability, multiple scattering, and EM radiation. Owing to their tunable morphology, tunable conductivity, and excellent EMWAPs, the PANI hierarchical microtubes offer great promise for fields such as sensors, electronics, optics, catalysis, energy storage, and EMW absorption and shielding.

Preparation of hollow hierarchical porous CoMgAl-borate LDH ball-flower and its calcinated product with extraordinary adsorption capacity for Congo red and methyl orange

Three-dimensionally ordered hollow borate anions intercalated CoMgAl-LDH ball-flower with hierarchical porous structure have been prepared by using zeolitic imidazolate framework-67 (ZIF-67) as a self-sacrificing template. After calcination it, the obtained CoMgAl-borate LDO can inherit the hollow hierarchical porous structure. Its unique structure has the merits of low density, large specific surface area, large pore size distribution and short diffusion pathway, which should be beneficial to the adsorption of larger dye molecules. The maximum uptake capacity of CoMgAl-borate LDO can even reach as high as 1493.3 mg g−1 for Congo red (CR) and 990.1 mg g−1 for methyl orange (MO) owing to the hierarchical hollow porous structure, the “memory effect”, electrostatic interactions, hydrogen bond and ion exchange between anionic dye and cationic adsorbent surface, surpassing those of most previously reported LDH-based adsorbents. The entire adsorption processes for CR and MO follow Langmuir isotherm and pseudo-second-order kinetics model. Moreover, the removal efficiency of CoMgAl-borate LDO can still reach 86.5% for CR and 84.3% for MO after recycling five times, indicating that CoMgAl-borate LDO is a very promising high-efficiency adsorbent. This work not only demonstrates that CoMgAl-borate LDO is a very green and efficient adsorbent for the removal of anionic dyes from wastewater, but also provides a strategy for the rational design and development of hollow nanostructures.

Self-template synthesis of hollow Fe-doped CoP prisms with enhanced oxygen evolution reaction activity

The development of efficient, durable and low cost electrocatalysts is crucial but extremely challenging for the oxygen evolution reaction (OER). Herein, we develop a self-template strategy to synthesize hollow Fe-doped CoP prisms (Fe-CoP) via ion exchange of cobalt acetate hydroxide with [Fe(CN)6]3- and phosphorization-induced transformation of CoFe-PBA (Co/Fe-containing prussian blue analogue) prisms in N2 atmosphere. The obtained Fe-CoP not only inherits the hollow prism-like morphology of CoFe-PBA, but also forms rich mesoporous channel. The Fe-CoP prisms exhibit extraordinary OER performances in 1.0 M KOH, with a low overpotential of 236 mV to deliver a current density of 10 mA cm−2 and a low Tafel slope of 32.9 mV dec–1. Moreover, the presented electrocatalyst shows good long-term operating durability and activity. The XPS and TEM analysis confirm that Fe-CoP has undergone surface reconstruction in the process of electrocatalytic OER, and the in situ formed oxides and oxyhydroxides are the real active species to boost OER. This work provides a promising pathway to the design and synthesis of efficient and robust electrocatalysts with hierarchical hollow structure for boosting OER.

Multi-heteroatom-doped hollow carbon tubes as robust electrocatalysts for the oxygen reduction reaction, oxygen and hydrogen evolution reaction

Multi-heteroatoms-doping tunes the electronic structure of the catalyst, thereby optimizing the intrinsic catalytic activity of tri-functional metal-free electrocatalyst. • This work provides a self-sacrifice template engineering strategy to synthesize NSCHCT as tri-functional metal-free electrocatalyst. • NSCHCT shows an excellent bifunctional performance towards ORR/OER and has a small ORR/OER voltage difference of 0.85 V. • The hollow hierarchical porous structure and multi-heteroatom-doped provide rich reactive sites. • ZAB based on NSCHCT1000 displays long-term stability of 55 h, which can drive a LED. Developing non-noble metal-based electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is highly desirable, while still facing challenges. Herein, a self-sacrifice template engineering strategy that feasible carbonization of the copolymer of melamine-trithiocyanurim wrapped by polydopamine was developed to fabricate N, S hollow co-doped carbon tube (NSCHCT) based trifunctional electrocatalyst. Owing to the hierarchical structure, including hollow and porous structure, the obtained catalyst exhibits rich active sites and favourable mass transfer advantage, boosting the kinetic of the catalytic process. Moreover, multiple heteroatoms-doping provides various active sites. Notably, the thiophene sulfur combining with pyridinic N(p-N/S) and thiophene sulfur combined with graphitic N (g-N/S) shows the lowest activation energy barrier for OER/ORR and HER, respectively. As a result, the NSCHCT assembled Zinc-air battery shows excellent performance with a power density of 109 mW cm −2 and a high open-circuit voltage of 1.44 V, comparable with the Pt/C + RuO 2 system.

Hierarchical Tiny-Sb encapsulated in MOFs derived-carbon and TiO2 hollow nanotubes for enhanced Li/Na-Ion half-and full-cell batteries

MOFs-derived Sb nanoparticles encapsulated in carbon and TiO 2 hollow nanotubes (Sb⊂CTHNs) were synthesized via dramatically homogeneous hybridization of TiO 2 coating with Fe-MOFs as the precursor, the import of TiO 2 like a holder support the framework and allow Sb⊂CTHNs inherit the MOFs advantages of high surface area, hollow inner nanostructure and permanent porosity. Such anodes revealed great reversible capacity, long cycle life and excellent rate capability as a novel Li/Na-ion battery anode. • Sb⊂CTHNs were obtained via annealing reduction and galvanic replacement routes. • The import of TiO 2 like a holder support the framework of Sb⊂CTHNs. • Tiny Sb nanoparticles fully embedded in tight carbon and TiO 2 matrix walls. • Hierarchical hollow structure of Sb⊂CTHNs can buffer the volume expansion. • Sb⊂CTHNs show excellent electrochemical performances for Li/Na half and full cells. The serious volume changes during the alloy/dealloy process and poor electronic conductivity always limit antimony (Sb) development as Li/Na-ion batteries anode. In this work, we chose metal-organic frameworks (MOFs, MIL-88) as template and successfully synthesized hierarchical tiny-Sb encapsulated in MOFs derived-carbon and TiO 2 hollow nanotubes (Sb⊂CTHNs) by annealing reduction and galvanic replacement methods. The hybridization of TiO 2 like a holder maintain the framework of MIL-88 and the advantages of hollow inner nanostructure, intrinsic porosity and high specific surface area were delivered to Sb⊂CTHNs gradually. Tiny-Sb nanoparticles fully embedded in tight carbon matrix and TiO 2 walls with ultrastable structure could buffer the volume expansion, enhanced Li + /Na + diffusion and presented superior electrochemical performance as Li/Na-ion battery anode. For Li-ion battery, Sb⊂CTHNs delivered a reversible capacity of 607.2 mA h g −1 after 100 cycles at a current density of 100 mA g −1 and ultrahigh rate capability (434.8 mA h g −1 at 5000 mA g −1 ). Combined with LiMn 2 O 4 cathode, these Sb⊂CTHNs//LiMn 2 O 4 full cells also displayed superior capacity and long cycle life. For Na-ion battery, Sb⊂CTHNs exhibited a high initial reversible capacity of 640.8 mA h g −1 and high rate capability (374.1 mA h g −1 at 5000 mA g −1 ). Combined with Na 3 V 2 (PO 4 ) 3 /AC cathode, Sb⊂CTHNs//Na 3 V 2 (PO 4 ) 3 full cells also displayed excellent electrochemical performances.

MOF-derived FeNiCoOX hierarchical hollow nanocages for oxygen evolution reaction

Highly efficient, inexpensive and stable electrocatalysts of oxygen evolution reaction are of great significance for the potential application of water splitting in new energy technology. In this work, we develop FeNiCoOX hierarchical hollow nanocages via a cation exchange reaction with annealing in air, which show excellent OER performances in 1 M KOH. This FeNiCoOx catalyst exhibits a small overpotential of 248 mV at 10 mA cm−2, a Tafel slope of 45.4 mV dec−1, as well as the remarkable stability. Excellent electrocatalytic performances are attributed to the synergistic effects from the multi-metal element compositions and the hierarchical hollow structures.

Co3O4@NiCo2O4 double-shelled nanocages with hierarchical hollow structure and oxygen vacancies as efficient bifunctional electrocatalysts for rechargeable Zn–air batteries

Highly efficient bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucially important for the rechargeable Zn-air battery, a potential power source for applications in electric vehicles and grid-scale stationary storage systems. Herein, Co3O4@NiCo2O4 double-shelled nanocages (Co3O4@NiCo2O4 DSNCs) with hierarchical hollow structure and oxygen vacancies were designed and synthesized via annealing metal-organic frameworks. Co3O4@NiCo2O4 DSNCs with large specific surface area and three-dimensional interconnected mesopores and cavity not only provide more reaction sites, but also offer an efficient transport environment for reactants. Moreover, oxygen vacancies on the surfaces improve the capture of oxygen species to enhance the reactivity of the catalyst. Consequently, Co3O4@NiCo2O4 DSNCs displayed excellent bifunctional electrocatalytic performance, with a positive half-wave potential of 0.81 V (vs. reversible hydrogen electrode, RHE) for ORR (approaching the potential of commercial Pt/C catalyst) and a low potential of 1.65 V at 10 mA cm-2 for OER (exceeding Pt/C). In a practical demonstration, the Zn-air battery using Co3O4@NiCo2O4 DSNCs as the cathode delivered a satisfactory power density of 102.1 mW cm-2, comparable to the Zn-air battery with a Pt/C cathode, and exhibited much longer cycling stability.

Templating synthesis of natural cotton-based hierarchically structured carbon hollow microfibers for high-performance solar vapor generation

Facile synthesis of a hierarchical hollow structure on natural abundant cotton fibers achieved an extremely high evaporation rate under 1 sun.

Self-templated synthesis of hollow hierarchical porous olive-like carbon toward universal high-performance alkali (Li, Na, K)-ion storage

Alkali (Li, Na, K)-ion batteries have attracted tremendous attention in current power supply systems. However, it remains a great challenge to explore universal anodes for the desired de-/intercalation of these three alkali-metal ions (Li+, Na+, K+). Herein, hollow hierarchical porous olive-like carbon (HHPOC) structure is prepared through a self-templated strategy and post acid-etching treatment. The unique hollow hierarchical porous structure can facilitate the electrolyte penetration, shorten the transport pathway of ions, and endure well the volume change during the insertion/extraction of alkali ions. Meanwhile, the abundant self-doped N/O heteroatoms provide sufficient active sites for Li+/Na+/K+ storage, thereby resulting in a capacitive-dominating storage mechanism for the HHPOC electrode especially in sodium/potassium ion batteries. The HHPOC electrode delivers high reversible discharge capacity of 1121.8 mA h g−1 at 0.1 A g−1 for lithium-ion battery, 386.8 mA h g−1 at 0.1 A g−1 for sodium-ion battery, and 305.6 mA h g−1 at 0.1 A g−1 for potassium-ion battery. Moreover, the HHPOC electrode exhibits promising cycling stability with negligible capacity decay over 800 cycles at 1 A g−1 for the three alkali-ion batteries. Therefore, this work provides a new perspective for the development of universal carbon anodes with efficient Li+/Na+/K+ storage and the delicate structural design of biomass carbon materials.

Etching strategy synthesis of hierarchical Ni-Mn hydroxide hollow spheres for supercapacitors

Hierarchical hollow structures have been shown excellent performance in supercapacitors. Herein, hierarchical Ni-Mn hydroxide hollow spheres are successfully prepared by an etching strategy. NiMn-glycerate solid spheres are first obtained as templates. After treatment in the mixed solvents of 1-methyl-2-pyrrolidone and water, NiMn-glycerate templates are etched to form hierarchical Ni-Mn hydroxide hollow spheres. Owing to the advantages of hierarchical hollow structures and large surface area, Ni-Mn hydroxide as electrode material manifests a specific capacity of 1680 F g−1 at 2.0 A g−1, and it maintains 1068 F g−1 at 15 A g−1. Meanwhile, a diminished specific capacity of only 3.4 % is achieved over 5500 cycles at 10 A g−1. Furthermore, the fabricated asymmetric supercapacitor comprising of Ni-Mn hydroxide and activated carbon demonstrates a specific energy of 42.8 Wh kg−1 at 1703 W kg−1, indicating as a promising electrode material for high performance supercapacitors.

Cu/Co mixed hierarchical tubular heterostructures for alkaline supercapacitors

The hierarchical hollow structures of electrode materials s of supercapacitors is effective for the large specific surface area and fast ions and charge transports. Cu nanowires as self-engaged templates provide sites and paths for the nucleation and growth of the ZIF-67. Meanwhile, Cu atoms can disperse into metal organic frameworks (MOFs) to form Cu-Co mixed oxides and construct heterostructures. In this case, Cu nanowires are used as a template and an activated part to improve the internal electronic structures. The electrochemical performance can be improved due to these features. Herein, Cu nanowires and MOFs are combined via a mild and efficient approach to fabricate Cu-Co-O/CuO electrode materials. This electrode exhibits excellent electrochemical performance with a specific capacitance of 834.1 F g−1 at 1 A g−1. The assembled asymmetric supercapacitor (ASC) shows an ultra-high energy density of 40.7 W h kg−1 at a power density of 915 W kg−1 and a good capacitance retention after 8000 cycles in a 2 M KOH aqueous solution. The results otained in this work indicate a strategy of the combination of reactive metals with metal organic frameworks used as electrode materials for electrochemical supercapacitors.

Three-dimensional hierarchical Ca3Co4O9 hollow fiber network as high performance anode material for lithium-ion battery

Transition metal oxides have high specific capacity as anode materials for lithium-ion battery. But aggregation of particles and volume expansion during lithiation/delithiation restrict their application. In this work, a three-dimensional hierarchical Ca3Co4O9 hollow fiber network assembled by nanosheets is prepared by a electrospinning combining with heat treatment method to overcome these issues and to boost its lithium storage performance. As-synthesized sample possesses excellent cyclic stability (578.6 mA h g−1 at 200 mA g−1 after 500 cycles) and rate performance (293.5 mA h g−1 at 5000 mA g−1), much better than those of commercial Co3O4. Furthermore, the fast kinetics of the three-dimensional Ca3Co4O9 hollow fiber network is also confirmed by the variable scan rates CV tests and the EIS measurements, which is dedicated to the specific hierarchical hollow fiber network structure that provides shorter ion transport distances and higher electrical conductivity. This work supplies a universal approach to improve the electrochemical performance of transition metal oxides for lithium ion batteries.

Rosa roxburghii-like hierarchical hollow sandwich-structure C@Fe2O3@C microspheres as second nanomaterialsfor superior lithium storage

Fe2O3, as a promising advanced anode for the next generation lithium ion batteries, behaves high theoretical capacity and rich electrochemical properties. However, the poor cycle performances and low conductivity impede its extensive applications in lithium ion batteries. Herein, the von Mises stress distribution on solid spheres and hollow spheres were simulated by finite element method which confirmed the vital role of porous hollow spheres on strain-relaxation behavior as electrode materials. We also have developed a template method for the first preparation of rosa roxburghii-like hierarchical hollow sandwiched C@Fe2O3@C microspheres as second nanomaterials for superior lithium storage. As an advanced anode for lithium ion batteries, the porous C@Fe2O3@C microspheres exhibit reversible gravimetric capacity (1167 mAh g−1 after 100 cycles at 0.2 C), high rate performance (762 mAh g−1 after 1000 cycles at 1 C) and cycling stability without obvious capacity fading. The excellent performance is ascribed to the hierarchical hollow structure which can better withstand the stress produced in the process of ion embedding/stripping and alleviate the volume change of materials. On the other hand, the double carbon layer can effectively inhibit the self-aggregation effect of nano-scale Fe2O3 and provide a three-dimensional electronic network.

Engineering full hollow and yolk-shell structures of Z-scheme photocatalysts for advanced hydrogen production

Hierarchical hollow and direct Z-scheme nanocomposites were two prominent representatives of an efficient photocatalyst due to their unique structure advantages and strong photoredox properties. In this report, two types of Z-scheme photocatalysts, namely In2S3-Bi2S3 (IBS) and In2O3-Bi2O3 (IBO) have been successfully prepared from the same bimetallic metal-organic frameworks (InBi-MOFs). The IBS was constructed with a full hollow structure owing to the different diffusion velocity of the metal ions and S2− ions, while the IBO was formed with a yolk-shell structure due to the existence of the temperature gradient from the exterior shell to the inner yolk in the pyrolysis process. The IBS and IBO showed superior H2 production rate of 22.73 and 3.6 mmol g-1h−1, which were approximately 13.2 and 4.1 times higher than that of single In2S3 and In2O3 due to the effects of hierarchical hollow structures and Z-scheme heterojunction. The unique full hollow and yolk-shell structures could be clearly revealed by transmission electron microscopy, while the Z-scheme electron migrate pathway was thoroughly confirmed by various experimental studies and density functional theory calculation.

Preparation and evaluation of highly dispersed HHSS supported Cu-Fe bimetallic catalysts for higher alcohols synthesis from syngas

Porous carriers play an important role in the catalytic transformation of syngas into higher alcohols, which promises higher sustainability in C1 chemistry. In this work, a series of hierarchical hollow silica spheres (HHSS) supported Cu-Fe bimetal catalysts were successfully prepared through ultrasonic-assisted impregnation for higher alcohols synthesis from syngas. Structural characterization results indicate that the hierarchical hollow structure of HHSS support can be maintained and the Cu-Fe bimetallic nanoparticles are highly dispersed on HHSS surface. The catalytic performances of samples in the test of CO hydrogenation for higher alcohols synthesis were investigated. The results revealed that the conversion rate of CO and the selectivity of C2+OH alcohol increased first and then decreased with the decrease of the amount of Cu content in the CuxFey@HHSS catalyst. The highest CO conversion, alcohol selectivity and STYROH over Cu-Fe@HHSS catalyst are 65.1 %, 46.6 %, and 118.1 gkg−1 h−1, respectively. It was found that a large number of CuFe2O4 were formed in Cu-Fe@HHSS catalyst and also confirmed that the CuFe2O4 spinel and CuO-CuFe2O4 were converted to Cu-Fe5C2 composite in the spent Cu-Fe@HHSS catalyst, which can enhance the synergy between Cu-Fe bimetals. Furthermore, copper and iron are highly dispersed on HHSS after the reaction, which enhances the structural stability of the catalyst. Based on the development and utilization of low-cost catalysts and the production of clean liquid fuels, HHSS has a great prospect of catalyst support in the energy field.