Sulfur/carbon composites prepared with ordered porous carbon for Li-S battery cathode

Ordered porous cabon with a 2-D hexagonal structure,high specific surface area and large pore volume was synthesized through a twostep heating method using tri-block copolymer as template and phenolic resin as carbon precursor.The results indicated the electrochemical performance of the sulfur/carbon composites prepared with the ordered porous carbon was significantly affected by the pore structure of the carbon.Both the specific capacity and cycling stability of the sulfur/carbon composites were improved using the bimodal micro/meso-porous carbon frameworks with high surface area.Its initial discharge capacity can be as high as 1200 mAh·g-1 at a current density of 167.5 mA·g-1The improved capacity retention was obtained during the cell cycling as well.

A Method for Preparation of Ordered Porous Silicon Based on a 2D SiO_2 Template

A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres. The corrosion time can be used to control the depths of the holes. It is found that the presence of a SiO2 layer, formed by the oxidation of the rough internal surface of the hole, is the primary reason allowing the corrosion to proceed. Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.

Atomically dispersed hierarchically ordered porous Fe-N-C single-atom nanozymes for dyes degradation

The development of novel nanozymes for environmental contamination remediation is a worthwhile research direction.However,most of the reported nanozymes cannot degrade efficiently due to the limitation of the internal active sites not being able to come into direct contact with contaminants.Therefore,we reported Fe-N-C single-atom nanozymes(SAzymes)with atomically dispersed FeN4 active sites anchored on a three-dimensional hierarchically ordered microporous-mesoporous-macroporous nitrogen doped carbon matrix(3DOM Fe-N-C)for the degradation of a targeted environmental pollutant(rhodamine B(RhB)).The three-dimensional(3D)hierarchically ordered porous structure may accelerate mass transfer and improve the accessibility of active sites.This structure and high metal atom utilization endow Fe-N-C SAzyme with enhanced tri-enzyme-mimic activities,comprising oxidase-mimic,peroxidase-mimic,and catalase-mimic activities.Based on its excellent peroxidase-mimic activity,3DOM Fe-N-C can degrade RhB by hydroxyl radicals(·OH)generated in the presence of hydrogen peroxide.This study provides a new idea for designing porous Fe-N-C SAzymes for environmental contamination remediation.

Rational fabrication of ordered porous solid strong bases by utilizing the inherent reducibility of metal-organic frameworks

Ordered porous solid strong bases(OPSSBs)have attracted great research interest due to the excellent performance as heterogeneous catalysts in various reactions.The main obstacle for fabricating OPSSBs is the requirement of high temperature to produce strong basicity on ordered porous materials.For example,the temperatures of 600-650℃ are required for the decomposition of base precursor NaNO_(3)to basic sites on mesoporous silica SBA-15 and zeolite Y.Such high decomposition temperatures are energy-intensive and harmful to the structure of supports.Herein,we report the fabrication of OPSSBs by utilizing the redox interaction between base precursor and low-valence metal centers(e.g.,Cr^(3+))in metal-organic frameworks(MOFs).The base precursor NaNO_(3)on MIL-101(Cr)can be converted to basic sites entirely at 300℃,which is quite lower than those of the conventional thermal conversion on SBA-15 and zeolite Y(600-650℃).The exploration on decomposition mechanism reveals that the valence change of Cr^(3+)to Cr^(6+)takes place during the conversion of NaNO_(3)to basic sites.In this way,MOFs-derived base catalysts have been synthesized successfully by the host-guest redox strategy and exhibit high catalytic activity in typical base-catalyzed reactions.

Three-dimensional ordered hierarchically porous carbon materials for high performance Li-Se battery

Developing host materials with high specific surface area, good electron conductivity, and fast ion transportation channel is critical for high performance lithium-selenium(Li-Se) batteries. Herein, a series of three dimensional ordered hierarchically porous carbon(3D OHPC) materials with micro/meso/macropores are designed and synthesized for Li-Se battery. The porous structure is tuned by following the concept of the generalized Murray’s law to facilitate the mass diffusion and reduce ion transport resistance.The optimized 3D Se/OHPC cathode exhibits a very high 2 nd discharge capacity of 651 m Ah/g and retains 361 m Ah/g after 200 cycles at 0.2 C. Even at a high current rate of 5 C, the battery still shows a discharge capacity as high as 155 m Ah/g. The improved electrochemical performance is attributed to the synergy effect of the interconnected and well-designed micro, meso and macroporosity while shortened ions diffusion pathways of such Murray materials accelerate its ionic and electronic conductivities leading to the enhanced electrochemical reaction. The diffusivity coefficient in Se/OHPC can reach a very high value of 1.3 × 10^(-11)cm^(2)/s, much higher than those in single pore size carbon hosts. Their effective volume expansion accommodation capability and reduced dissolution of polyselenides ensure the high stability of the battery. This work, for the first time, established the clear relationship between textural properties of cathode materials and their performance and demonstrates that the concept of the generalized Murray’s law can be used as efficient guidance for the rational design and synthesis of advanced hierarchically porous materials and the great potential of 3D OHPC materials as a practical high performance cathode material for Li-Se batteries.

Highly efficient electroreduction of CO_(2) by defect single-atomic Ni-N_(3) sites anchored on ordered micro-macroporous carbons

Microporous supports typically fail to fully expose active sites for electrolytes and CO_(2) molecules,and this usually results in low current density for the electrocatalytic CO_(2) reduction reaction(CO_(2)RR).To overcome the biggest obstacle and facilitate commercial applications,defective single-atomic Ni-N_(3) sites anchored to ordered micro-macroporous N-doped carbon(Ni-N/OMC)have been prepared by the pyrolysis of the Ni-ZIF-8@PS(ZIF=zeolitic imidazolate framework)and are intended to provide enhanced CO_(2)RR with a current density at an industrial level.This Ni-ZIF-8@PS is constructed of nickel-based ZIF-8 embedded in the three-dimensional(3D)highly ordered polystyrene spheres(PS).The 3D ordered micro-macroporous architecture of Ni-N/OMC could facilitate the mass transfer of substrates to the accessible defective single-atomic Ni-N_(3) sites through micropores(0.6 nm)and macropores(~200 nm)interconnected by 50 nm channels.In a flow cell,Ni-N/OMC exhibits almost 100.0%CO Faraday efficiency(FECO)between−0.2 and−1.1 V vs.RHE and an industrial level CO partial current density of 208 mA cm^(−2).It has a turnover frequency of 1.5×10^(5) h^(−1) at−1.1 V vs.RHE in 1 M KOH electrolyte,which exceeds that of most reported nickel-based electrocatalysts.This excellent CO_(2)RR performance for Ni-N/OMC makes it a state-of-the-art electrocatalyst for CO_(2)RR.Theoretical calculations show that the defective Ni-N_(3) site can lower the energy of*COOH formation compared with that of the Ni-N4 site,thereby accelerating CO_(2)RR.Ni-N/OMC can also be utilized as a cathodic catalyst in Zn-CO_(2) battery,exhibiting high CO selectivity in the discharge process and excellent stability.This work paves a pathway to rational design of highly efficient electrocatalysts with 3D hierarchically ordered micro-macroporous architecture for CO_(2)RR towards industrial production and commercial applications.

Boosting reaction kinetics and shuttle effect suppression by single crystal MOF-derived N-doped ordered hierarchically porous carbon for high performance Li-Se battery

Maximizing the fixing ability of polyselenides to reduce the shuttle effect in Li-Se batteries remains highly challenging.Single crystal metal-organic framework(MOF)-derived N-doped ordered hierarchically porous carbon(SNOHPC)synthesized by a confined crystal growth and template-assisted method demonstrates excellent electrochemical performance as a host material for Li-Se battery.The large number of micropores inherited from the MOF structure provides large space and surface for Se loading and reaction sites,ensuring the high energy density of the battery.The insitu X-ray diffraction(XRD)technique is used to understand the reaction mechanism.The synergy of the interconnected three-scale-level micro-meso-macroporous structure and Ndoped polar sites can buffer the volume expansion,shorten the ion transportation with a very high diffusion coefficient of4.44×10cm^(2)sand accelerate the lithiation/delithiation reaction.Selenium is sufficiently reactive and the polyselenide intermediates are tightly fixed inside the carbon host material,thereby achieving excellent specific capacity,stability,and rate capability.Such a cathode exhibits a very high 2discharge/charge capacity of 658 and 683 mA h g,respectively,and retains a very high capacity of 367 mA h gafter 200 cycles at the current of 0.2 C.Even at the high current of 5 C,a very high discharge capacity of 230 mA h gis obtained.This work provides a new kind of high-performance porous materials with rational pore arrangement applicable for highly efficient energy storage.

Fabrication of Macroporous Protein-containing Films through the Reverse Emulsions Approach Featuringβ-Cyclodextrin-conjugated PEG-PLGA Copolymers

A series of β-cyclodextrin-conjugated 4-arm poly（ethylene glycol）-poly（lactide-co-glycolide） （4-arm PEG-PLGA） copolymers were synthesized by a ring-opening polymerization of D,L-lactide and glycolide using 4-arm PEG as initiator, and then conjugated with mono（6-ethylenediamine-6-deoxy）- β-cyclodextrin （CDen） or ethylenediamino-bridged bis- β-CD （BCDen）. The chemical structures of copolymers were confirmed by IH-NMR and FTIR spectroscopy. The , β-CD-conjugated PEG-PLGA formed stable reverse micelles due to the formation of fl-CD and bovine serum albumin （BSA） inclusion complexation, which could accommodate BSA in the organic solvent with improved encapsulation efficiency. Moreover, we demonstrated a one-step approach to construct macroporous protein-containing films using these reverse micelles. The films with ordered pore arrays were directly prepared from reverse micelles. Interestingly, the protein was totally located in the whole matrix except for the pores.

A novel 3D printed technology to construct a monolithic ultrathin nanosheets Co_(3)O_(4)/SiO_(2) catalyst for benzene catalytic combustion

In this study,a novel three-dimensional(3D)-OMm-Co_(3)O_(4)/SiO_(2)-0.5AP(OMm=ordered macro–meso porous,AP=aluminum phosphate)monolithic catalyst was for the first time constructed successfully with the hierarchical Co-phyllosilicate ultrathin nanosheets growth on the surface of 3D printed ordered macropore–mesoporous SiO_(2)support.On the one hand,we discovered that the construction of ordered macropore–mesoporous structures is beneficial to the diffusion and adsorption of reactants,intermediates,and products.On the other hand,the formation of hierarchical Co-phyllosilicate ultrathin nanosheets could provide more active Co&+species,abundant acid sites,and active oxygen.The above factors are in favor of improving the catalytic performance of benzene oxidation,and then a 3D-OMm-Co_(3)O_(4)/SiO_(2)-0.5AP catalyst exhibited the superior catalytic activity.To explore the effect of catalysts structure and morphology,various Co-based catalysts were also constructed.Simultaneously,the 3D-OMm-Co_(3)O_(4)/SiO_(2)-0.5AP catalyst has excellent catalytic performance,water resistance,and thermal stability in the catalytic combustion of benzene due to the strong interactions between Co&+species and SiO_(2)in the phyllosilicate.Therefore,this study proposes a new catalyst synthesis method through 3D printing,and presents considerable prospects for the removal of VOCs from industrial applications.

Platinum nickel alloy-MXene catalyst with inverse opal structure for enhanced hydrogen evolution in both acidic and alkaline solutions

The development of an efficient Pt-based electrocatalyst in acidic and alkaline electrolytes is of great significance to the field of electrocatalytic hydrogen evolution.Herein,we report a strategy for in situ growth of Pt_(3)Ni truncated octahedrons on Ti3C2Tx nanosheets and then obtain an ordered porous catalyst via a template method.Meanwhile,we use the finite element calculation to clarify the relationship between the component structure and performance and find that the performance of the spherical shell microstructure catalyst is higher than that of the disc structure catalyst,which is also verified by experiments.The experimental analysis shows that the ordered porous catalyst is conducive to enhancing electrocatalytic hydrogen evolution activity in acidic and alkaline electrolytes.In an acidic solution,the overpotential is 25 mV(10 mA·cm^(−2)),and the Tafel slope is 22.86 mV·dec−1.In an alkaline solution,the overpotential is 44.1 mV(10 mA·cm^(−2)),and the Tafel slope is 39.06 mV·dec−1.The synergistic coupling between Ti3C2Tx and Pt_(3)Ni nanoparticles improves the stability of the catalyst.The in situ growth strategy and design of microstructure with its correlation with catalytic performance represent critical steps toward the rational synthesis of catalysts with excellent catalytic activity.