Kinetic-boosted CO_(2) electroreduction to formate via synergistic electric-thermal field on hierarchical bismuth with amorphous layer

Electrocatalytic converting CO_(2) into chemical products has emerged as a promising approach to achieving carbon neutrality.Herein,we report a bismuth-based catalyst with high curvature terminal and amorphous layer which fabricated via two-step electrodeposition achieves stable formate output in a wide voltage window of 600 mV.The Faraday efficiency(FE) of formate reached up to 99.4% at-0.8 V vs.RHE and it remained constant for more than 92 h at-15 mA cm^(-2).More intriguingly,FE formate of95.4% can be realized at a current density of industrial grade(-667.7 mA cm^(-2)) in flow cell.The special structure promoted CO_(2) adsorption and reduced its activation energy and enhanced the electric-thermal field and K^(+) enrichment which accelerated the reaction kinetics.In situ spectroscopy and theoretical calculation further confirmed that the introduction of amorphous structure is beneficial to adsorpting CO_(2)and stabling*OCHO intermediate.This work provides special insights to fabricate efficient electrocatalysts by means of structural and crystal engineering and makes efforts to realize the industrialization of bismuth-based catalysts.

Remarkably Enhanced Methane Sensing Performance at Room Temperature via Constructing a Self-Assembled Mulberry-Like ZnO/SnO_(2) Hierarchical Structure

Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage.In this work,a self-assembled mulberry-like ZnO/SnO_(2)hierarchical structure is constructed by a two-step hydrothermal method.The resultant sensor works at room temperature with excellent response of~56.1%to 2000 ppm CH_(4)at 55%relative humidity.It is found that the strain induced at the ZnO/SnO_(2)interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O_(2)^(-)ions close to the interface,leading to significant improvement in the sensing performance of the methane gas sensor at room temperature.

Hierarchical Bimetallic Selenides CoSe_(2)–MoSe_(2)/rGO for Sodium/Potassium-Ion Batteries Anode: Insights into the Intercalation and Conversion Mechanism

As anode materials for high-performance sodium-ion batteries and potassium-ion batteries,bimetallic selenides have attracted great concern due to their relatively high electrical conductivity and electrochemical activity.However,the formidable challenge in the reaction process is the large volume change,leading to the structural collapse of material,and eventually the decline in electrochemical performance.Herein,a composite of hierarchical CoSe_(2)–MoSe_(2) tubes anchored on reduced graphene oxide nanosheets(CoSe_(2)–MoSe_(2)/rGO)is designed by an in situ hydrothermal selenization treatment.Benefiting from the synergistic effects between CoSe_(2) and MoSe_(2),unique hierarchical structure,and effective reduced graphene oxide coating,the CoSe_(2)–MoSe_(2)/rGO exhibited improved reaction kinetics and structural stability,and thus good electrochemical properties.A combination mechanism of intercalation and conversion of CoSe_(2)–MoSe_(2)/rGO by forming NaxCoSe_(2) and Mo_(15)Se_(19) as intermediate states is put forward on the basis of in situ and ex situ XRD analyses.

Hydrophilic bi-functional B-doped g-C_(3)N_(4) hierarchical architecture for excellent photocatalytic H_(2)O_(2) production and photoelectrochemical water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has attracted great interest in photocatalysis and photoelectrocatalysis.However,their poor hydrophilicity poses a great challenge for their applications in aqueous environment.Here,we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C_(3)N_(4)nanoplatelets.Such hierarchical B-doped g-C_(3)N_(4)material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium,leading to an excellent photocatalytic H_(2)O_(2)production rate of 4240.3μM g^(-1)h^(-1),2.84,2.64 and 2.13 times higher than that of the bulk g-C_(3)N_(4),g-C_(3)N_(4)nanoplatelets and bulk B doped g-C_(3)N_(4),respectively.Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 m A cm^(-2)at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting.This work makes a fundamental improvement towards large-scale exploitation of highly active,hydrophilic and stable metal-free g-C_(3)N_(4)photocatalysts for various practical applications.

Hierarchical Ti_(3)C_(2)T_(x)@ ZnO Hollow Spheres with Excellent Microwave Absorption Inspired by the Visual Phenomenon of Eyeless Urchins

Ingenious microstructure design and rational composition selection are effective approaches to realize high-performance microwave absorbers,and the advancement of biomimetic manufacturing provides a new strategy.In nature,urchins are the animals without eyes but can“see”,because their special structure composed of regular spines and spherical photosensitive bodies“amplifies”the light-receiving ability.Herein,inspired by the above phenomenon,the biomimetic urchin-like Ti_(3)C_(2)T_(x)@ZnO hollow microspheres are rationally designed and fabricated,in which ZnO nanoarrays(length:~2.3μm,diameter:~100 nm)as the urchin spines are evenly grafted onto the surface of the Ti_(3)C_(2)T_(x) hollow spheres(diameter:~4.2μm)as the urchin spherical photosensitive bodies.The construction of gradient impedance and hierarchical heterostructures enhance the attenuation of incident electromagnetic waves.And the EMW loss behavior is further revealed by limited integral simulation calculations,which fully highlights the advantages of the urchin-like architecture.As a result,the Ti_(3)C_(2)T_(x)@ZnO hollow spheres deliver a strong reflection loss of−57.4 dB and broad effective absorption bandwidth of 6.56 GHz,superior to similar absorbents.This work provides a new biomimetic strategy for the design and manufacturing of advanced microwave absorbers.

3D hierarchical microspheres constructed by ultrathin MoS2-C nanosheets as high-performance anode material for sodium-ion batteries

MoS2/C composites are considered to have great application potential in sodium-ion batteries(SIBs).It is a challenging and meaningful subject that developing high-performance anode materials via combining MoS2 and carbon effectively to give free rein to their advantages in sodium ion storage.In this work,a novel MoS2-C material was designed by using cellulose nanocrystals(CNCs)as low-cost and green carbon source.3 D hierarchical microspheres(200-250 nm)constructed by ultrathin MoS2-C nanosheets were synthesized by synchronizing the pre-carbonization of CNCs with the formation of MoS2 in hydrothermal reaction and subsequent pyrolysis process.It is found that the ultrathin MoS2-C nanosheets were composed of CNCs-derived short-range ordered carbon and few-layered MoS2.Benefiting from the unique structure and robust combination of MoS2 and CNCs-derived carbon,the ultrathin MoS2-C nanosheets composite was proved to have excellent cycling stability and superior rate performance in sodium-ion half-cell test and have high first reversible specific capacity of 397.9 m Ah/g in full-cell test.This work provides a significant and effective pathway to prepare MoS2-C materials with excellent electrochemical performance for the application in large-scale energy storage systems.

Anti-aggregation growth and hierarchical porous carbon encapsulation enables the C@VO_(2) cathode with superior storage capability for aqueous zinc-ion batteries

Self-aggregation and sluggish transport kinetics of cathode materials would usually lead to the poor electrochemical performance for aqueous zinc-ion batteries(AZIBs).In this work,we report the construction of C@VO_(2) composite via anti-aggregation growth and hierarchical porous carbon encapsulation.Both of the morphology of composite and pore structure of carbon layer can be regulated by tuning the adding amount of glucose.When acting as cathode applied for AZIBs,the C@VO_(2)-3:3 composite can deliver a high capacity of 281 m Ah g^(-1) at 0.2 A g^(-1).Moreover,such cathode also exhibits a remarkably rate capability and cyclic stability,which can release a specific capacity of 195 m Ah g^(-1) at 5 A g^(-1) with the capacity retention of 95.4%after 1000 cycles.Besides that,the evolution including the crystal structure,valence state and transport kinetics upon cycling were also deeply investigated.In conclusion,benefited from the synergistic effect of anti-aggregation morphology and hierarchical porous carbon encapsulation,the building of such C@VO_(2) composite can be highly expected to enhance the ion accessible site,boost the transport kinetics and thus performing a superior storage performance.Such design concept can be applied for other kinds of electrode materials and accelerating the development of highperformance AZIBs.

Hierarchical TiO2 nanorods with a highly active surface for photocatalytic CO_(2) reduction

Photocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been considered as one of most effective ways to solve the current energy crisis and environmental problems.However,the practical application of photocatalytic CO_(2)RR is largely hindered by lock of efficient catalyst.Here,hierarchical titanium dioxide(TiO_(2))nanostructures with a highly active{001}surface were successfully synthesized by a facile approach from metal Ti powders.The obtained hierarchical TiO_(2)nanostructures were composed of TiO_(2)nanorods,which have a diameter about 5–10 nm and a length of several micrometers.It is found that these nanorods have exposed{001}facets.On the other hand,these hierarchical TiO_(2)nanostructures have a good light-harvesting efficiency with the help of TiO_(2)nanorods component and large specific surface area.Therefore,these hierarchical TiO_(2)nanostructures exhibit a much better activity for photocatalytic CO_(2)reduction than that of commercial TiO_(2)(P25).This high activity can be attributed to the synergistic effects of active surface,efficient charge transfer along nanorods and good light harvesting in the nanorod-hierarchical nanostructures.

A hierarchically structured tin-cobalt composite with an enhanced electronic effect for high-performance CO_(2) electroreduction in a wide potential range

Earth-abundant and nontoxic Sn-based materials have been regarded as promising catalysts for the electrochemical conversion of CO_(2)to C1 products,e.g.,CO and formate.However,it is still difficult for Snbased materials to obtain satisfactory performance at low-to-moderate overpotentials.Herein,a simple and facile electrospinning technique is utilized to prepare a composite of a bimetallic Sn-Co oxide/carbon matrix with a hollow nanotube structure(Sn Co-HNT).Sn Co-HNT can maintain>90%faradaic efficiencies for C1 products within a wide potential range from-0.6 VRHE to-1.2 VRHE,and a highest 94.1%selectivity towards CO in an H-type cell.Moreover,a 91.2%faradaic efficiency with a 241.3 m A cm^(-2)partial current density for C1 products could be achieved using a flow cell.According to theoretical calculations,the fusing of Sn/Co oxides on the carbon matrix accelerates electron transfer at the atomic level,causing electron deficiency of Sn centers and reversible variation between Co^(2+)and Co^(3+)centers.The synergistic effect of the Sn/Co composition improves the electron affinity of the catalyst surface,which is conducive to the adsorption and stabilization of key intermediates and eventually increases the catalytic activity in CO_(2)electroreduction.This study could provide a new strategy for the construction of oxide-derived catalysts for CO_(2)electroreduction.

Nitrogen-doped hierarchically porous carbon spheres for low concentration CO_(2) capture

Synthesis of spherical carbon beads with effective CO_2 capture capability is highly desirable for large scale application of CO2 sorption, but remains challenging. Herein, a facile and efficient strategy to prepare nitrogen-doped hierarchically porous carbon spheres was developed via co-pyrolyzation of poly(vinylidene chloride) and melamine in alginate gel beads. In this approach, melamine not only serves as the nitrogen precursor, but also acts as a template for the macropores structures. The nitrogen contents in the hierarchically porous carbon spheres reach a high level, ranging from 11.8 wt% to 14.7 wt%, as the melamine amount increases. Owing to the enriched nitrogen functionalities and the special hierarchical porous structure, the carbon spheres exhibit an outstanding CO_2 capture performance, with the dynamic capacity of as much as about 7 wt% and a separation factor about 49 at 25 °C in a gas mixture of CO_2/N_2(0.5:99.5, v/v).

TiO_(2)bunchy hierarchical structure with effective enhancement in sodium storage behaviors

Bronze phase TiO_(2)[TiO_(2)(B)]has great research potential for sodium storage since it has a higher theoretical capacity and ion mobility compared with other phases of TiO_(2).In this case,preparing porous TiO_(2)(B)nanosheets,which can provide abundant sodium insertion channels,is the most effective way to improve transport kinetics.Here,we use the strong one-dimensional TiO_(2)nanowires as the matrix for stringing these nanosheets together through a simple solvothermal method to build a bunchy hierarchical structure[TiO_(2)(B)-BH],which has fast pseudocapacitance behavior,high structural stability,and effective ion/electron transport.With the superiorities of this structure design,TiO_(2)(B)-BH has a higher capacity(131 vs.70 mAh g^(−1)[TiO_(2)-NWs]at 0.5 C).And it is worth mentioning that the reversible capacity of up to 500 cycles can still be maintained at 85 mAh g^(−1)at a high rate of 10 C.Meanwhile,we also further analyzed the sodium storage mechanism through the ex-situ X-ray powder diffraction test,which proved the high structural stability of TiO_(2)(B)-BH in the process of sodiumization/de-sodiumization.This strategy of uniformly integrating nanosheets into a matrix can also be extended to preparing electrode material structures of other energy devices.

Superamphiphobic, light-trapping FeSe2 particles with a micro-nano hierarchical structure obtained by an improved solvothermal method

Wettability and the light-trapping effect of FeSe2 particles with a micro-nano hierarchical structure have been inves- tigated. Particles are synthesized by an improved solvothermal method, wherein hexadecyl trimetbyl ammonium bromide （CTAB） is employed as a surfactant. After modifying the particles with heptadecafluorodecyltrimethoxy-silane （HTMS）, we find that the water contact angle （WCA） of the FeSe2 particles increases by 6.1~ and the water sliding angle （WSA） decreases by 2.5~ respectively, and the diffuse reflectivity decreases 29.4% compared with similar FeSe2 particles synthe- sized by the conventional method. The growth process of the particles is analyzed and a growth scenario is given. Upon altering the PH values of the water, we observe that the superhydrophobic property is maintained quite consistently across a wide PH range of 1-14. Moreover, the modified particles were also found to be superoleophobic. To the best of our knowledge, there is no systematic research on the wettability of FeSe2 particles, so our research provides a reference for other researchers.

Dimethoxymethane production via CO_(2)hydrogenation in methanol over novel Ru based hierarchical BEA

Dimethoxymethane(DMM),a diesel blend fuel,is being researched with high interest recently due to its unique fuel properties.It is commercially produced via a two step-process of methanol oxidation to make formaldehyde,followed by its condensation with methanol.This study presents a one-pot method of DMM synthesis from methanol mediated carbon dioxide hydrogenation over novel heterogeneous catalysts.The effect of catalyst pore structure was investigated by synthesizing 3 wt%Ru over novel hierarchical zeolite beta(HBEASX)and comparing against Ru doped commercial zeolite beta(CBEA)and desilicated hierarchical zeolite beta(HBZDS).The results showed that 3%Ru/HBEASX provided the best activity for DMM production due to its large average pore size.It also showed the decisive role of SiO_(2)/Al_(2)O_(3)molar ratio,with SiO_(2)/Al_(2)O_(3)=75 providing the highest DMM yield of 13.2 mmol/gcat.LMeOH with ca.100%selectivity.The activity of 3%Ru/HBEAS3 after 5 recycle steps demonstrated the reusability of this catalyst.

Hierarchical Semiconductor Oxide Photocatalyst:A Case of the SnO_2 Microflower

Hierarchically assembled SnO_2 microflowers were synthesized by a facile hydrothermal process.Field emission scanning electron microscope results showed these hierarchical nanostructures were built from two dimensional nanosheets with the thicknesses of about 50 nm. Photoluminescence spectrum of the asobtained products demonstrated a strong visual emission peak at 564 nm. The photochemical measurement results indicated that the as-prepared sample exhibits excellent photocatalytic performance. These three dimensional SnO_2 hierarchical nanostructures may have potential applications in waste water purification.

Synthesis of Hierarchically Porous FAU/γ-Al2O3 Composites with Different Morphologies via Directing Agent Induced Method

Zeolite FAU composites with a macro/meso-microporous hierarchical structure were hydrothermally synthesized using macro-mesoporous γ-Al_2O_3 monolith as the substrate by means of the liquid crystallization directing agent(LCDA) induced method. No template was needed throughout the synthesis processes. The structure and porosity of zeolite composites were analyzed by means of X-ray powder diffraction(XRD), scanning electron microscopy(SEM) and N_2adsorption-desorption isotherms. The results showed that the supported zeolite composites with varied zeolitic crystalline phases and different morphologies can be obtained by adjusting the crystallization parameters, such as the crystallization temperature, the composition and the alkalinity of the precursor solution. The presence of LCDA was defined as a determinant for synthesizing the zeolite composites. The mechanisms for formation of the hierarchically porous FAU zeolite composites in the LCDA induced synthesis process were discussed. The resulting monolithic zeolite with a trimodal-porous hierarchical structure shows potential applicability where facile diffusion is required.

UV-Enhanced Room Temperature Ozone Sensor Based on Hierarchical SnO_2-In_2O_3

SnO2-ln2O3 hierarchical microspheres were prepared by the hydrothermal and solvothermal method. The morphology, phase crystallinity of the obtained SnO2-In203 were measured by X-ray diffraetion（XRD）, scan electron microscopy（SEM）, respectively. A room temperature ozone sensor based on SnO2-In2O3 hierarchical microspheres was fabricated and investigated. The gas sensing properties of the sensor using SnO2-In2O3 strongly depended on the proportion of SnO2 and In2O3. The sensitivity and response/recovery speed were greatly enhanced by UV illumination. A gas sensing mechanism related to oxygen defect was suggested.

Oxidation of benzene to phenol with N_(2)O over a hierarchical Fe/ZSM-5 catalyst

Catalytic oxidation of benzene with N_(2)O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixedbed reactor was investigated.The spent catalyst was in-situ regenerated by an oxidative treatment using N_(2)O and in total 10 reaction-regeneration cycles were performed.A 100% N_(2)O conversion,93.3% phenol selectivity,and high initial phenol formation rate of 16.49±0.06mmol_(phenol gcatalyst)^(-1)h^(-1)at time on stream(TOS) of 5 min,and a good phenol productivity of 147.06 mmol_(phenol gcatalyst)^(-1)during catalyst lifetime of 1800 min were obtained on a fresh hierarchical Fe/ZSM-5-Hi2.8 catalyst.With the reaction-regeneration cycle,N_(2)O conversion is fully recovered within TOS of 3 h,moreover,the phenol productivity was decreased ca.2.2±0.8% after each cycle,leading to a total phenol productivity of ca.0.44 ton_(pheol kg_(catalyst)^(-1)estimated for 300 cycles.Catalyst characterizations imply that the coke is rapidly deposited on catalyst surface in the initial TOS of 3 h(0.28 mgc_(gcatalyst)^(-1)min^(-1)) and gradually becomes graphitic during the TOS of 30 h with a slow formation rate of 0.06 mgc g_(catalyst)^(-1)min^(-1).Among others(e.g.,the decrease of textural property and acidity),the nearly complete coverage of the active Fe-O-Al sites by coke accounts for the main catalyst deactivation.Besides these reversible deactivation characteristics related to coking,the irreversible catalyst deactivation is also observed with the reaction-regeneration cycle.The latter is reflected by a further decreased amount of the active Fe-O-Al sites,which agglomerate on catalyst surface with the cycle,likely associated with the hard coke residue that is not completely removed by the regeneration.

Metal–organic framework derived hierarchical porous TiO_2 nanopills as a super stable anode for Na-ion batteries

Hierarchical porous TiOnanopills were synthesized using a titanium metal-organic framework MIL-125（Ti） as precursor. The as-synthesized TiOnanopills owned a large specific surface area of 102 m/g and unique porous structure. Furthermore, the obtained TiOnanopills were applied as anode materials for Na-ion batteries for the first time. The as-synthesized TiOnanopills achieved a high discharge capacity of 196.4 m Ah/g at a current density of 0.1 A/g. A discharge capacity of 115.9 m Ah/g was obtained at a high current density of 0.5 A/g and the capacity retention was remained as high as 90% even after 3000 cycles. The excellent electrochemical performance can be attributed to its unique hierarchical porous feature.

Cluster based hierarchical resource searching model in P2P network

For the problem of large network load generated by the Gnutella resource-searching model in Peer to Peer （P2P） network, a improved model to decrease the network expense is proposed, which establishes a duster in P2P network, auto-organizes logical layers, and applies a hybrid mechanism of directional searching and flooding. The performance analysis and simulation results show that the proposed hierarchical searching model has availably reduced the generated message load and that its searching-response time performance is as fairly good as that of the Gnutella model.

Natural Fresh Proteins Directed Hierarchically Porous Nitrogen-doped TiO_(2) as with High Performance as Photocatalyts and Electrode Materials

Fresh EPF proteins from Liangzi Lake were employed as a template to synthesize hierarchically porous nitrogen-doped TiO_(2) in a single process.The experimental results show that N-TiO_(2) sample exhibits significantly enhanced visible-light photocatalytic activity in both chemical waste treatment and hydrogen production,and the visible-light photocatalytic activities vary with the concentrations of EPF proteins.The optimal concentration of protein is 600 mg·mL^(-1) and the degradation of RhB could be almost completed in just 25 min.Furthermore,the performance of as-synthesized TiO2 as an electrode for Li-ion battery can be also regulated by the EPF proteins.Natural extrapallial fluid(EPF)proteins extracted from the same kind of mussels living in different regions have significantly different effects on the performances of TiO_(2) as electrode materials for Li-ion battery.The present work highlights the unimaginable effects of natural organic matrix on the synthesis of advanced materials with optimized functional properties.