Constructing a multifunctional mesoporous composite of metallic cobalt nanoparticles and nitrogen-doped reduced graphene oxides for high-performance lithium-sulfur batteries

Electrochemical properties of lithium-sulfur(Li-S)batteries are mainly hindered by both the insulating nature of elemental sulfur(i.e.,molecular S8)and the shuttling effect or sluggish redox kinetics of lithium polysulfide intermediates(Li_(2)S_(n),3≤n≤8).In this paper,a three-dimensional mesoporous reduced graphene oxide-based nanocomposite,with the embedding of metallic Co nanoparticles and the doping of elemental N(Co/NrGO),and its simply ground mixture with powdered S at a mass ratio of 1:6(Co/NrGO/S)are prepared and used as cathode-/separator-coated interlayers and working electrodes in assembled Li-S cells,respectively.One of the effective cell configurations is to paste composite Co/NrGO onto both the S-loading cathode and separator,showing good cycling stability(1070mAh g^(−1) in the 100th cycle at 0.2 C),highrate capability(835mAh g^(−1),2.0 C),and excellent durability(905mAh g^(−1) in the 250th cycle at 0.5 or 0.2 C).Compared with the experimental results of Co-absent NrGO,electrochemical properties of various Co/NrGO-based cell configurations clearly show multiple functions of Co/NrGO,indicating that the absence of Co/NrGO coatings and/or Co nanoparticles may be inadequate to achieve superior S availability of assembled Li-S batteries.

In-situ formation of cobalt phosphide nanoparticles confined in three-dimensional porous carbon for high-performing zinc-air battery and water splitting

The rational design of efficient and stable carbon-based electrocatalysts for oxygen reduction and oxygen evolution reactions is crucial for improving energy density and long-term stability of rechargeable zinc-air batteries(ZABs).Herein,a general and controllable synthesis method was developed to prepare three-dimensional(3D)porous carbon composites embedded with diverse metal phosphide nanocrystallites by interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and subsequent pyrolysis.Phytic acid as the dopant of polyaniline provides favorable anchoring sites for metal ions owing to the coordination interaction.Specifically,adjusting the concentration of adsorbed cobalt ions can achieve the phase regulation of transition metal phosphides.Thus,with abundant cobalt phosphide nanoparticles and nitrogen-and phosphorus-doping sites,the obtained carbon-based electrocatalysts exhibited efficient electrocatalytic activities toward oxygen reduction and evolution reactions.Consequently,the fabricated ZABs exhibited a high energy density,high power density of 368 mW cm^(-2),and good cycling/mechanical stability,which could power water splitting for integrated device fabrication with high gas yields.

The regulation of coordination structure between cobalt and nitrogen on graphene for efficient bifunctional electrocatalysis in Zn-air batteries

Electrocatalysts with atomically dispersed metal moieties are of importance in enhancing electrocatalysis for a specific reaction including oxygen reduction. However, it is still challenging to modulate the coordination structure of metal atoms with heteroatoms on carbon supports. Herein, an innovative and facile bridging strategy to regulate the coordination structure of cobalt with nitrogen atoms on reduced graphene oxide(r GO) sheets was developed by the interfacial complexation of amino-rich folic acid with cobalt ions on graphene oxide sheets and the subsequent thermal treatment. Typically, the actual coordination interaction between cobalt and nitrogen species was revealed by using X-ray absorption spectroscopy(XAS), exhibiting the Co-N_(4) coordination structure well-dispersed on reduced graphene oxide.Such unique structure enables the efficient oxygen reduction and evolution reactions via the favorable adsorption and desorption of intermediates. With the enhanced bifunctional electrocatalytic activities,the fabricated Zn-air battery exhibited the excellent performance with large power density of 319.8 mW cm^(-2) and good long-term stability(over 300 h). This work establishes the synthesis strategy for bridging metal atom with heteroatom on graphene sheets to enhance the bifunctional electrocatalysis toward Zn-air batteries.

Transition metal nanoparticles supported La-promoted MgO as catalysts for hydrogen production via catalytic decomposition of ammonia

The uniformly dispersed transition metal(Co, Ni and Fe) nanoparticles supported on the surface of La-promoted Mg O were prepared via a deposition-precipitation method for hydrogen production from catalytic decomposition of ammonia. X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, temperature-programmed reduction and temperature-programmed desorption were used to investigate the structure-activity relation of catalysts in NH3 decomposition. The results show that the strong interaction between active species and support can effectively prevent the active species from agglomerating during ammonia decomposition reaction. In addition, the introduction of La species not only facilitates the adsorption and decomposition of NH3 and desorption of N2, but also benefits the better dispersion of the active species. The prepared catalysts showed very high catalytic activity for ammonia decomposition compared with the same active composition samples that reported previously. Meanwhile, the catalysts showed excellent high-temperature stability and no any deactivation was observed, which are very promising candidates for the decomposition of ammonia to hydrogen.

Rational design of Cu-based electrocatalysts for electrochemical reduction of carbon dioxide

The recent development of Cu-based electrocatalysts for electrochemical reduction of carbon dioxide（CO） has attracted much attention due to their unique activity and selectivity compared to other metal catalysts. Particularly, Cu is the unique electrocatalyst for COelectrochemical reduction with high selectivity to generate a variety of hydrocarbons. In this review, we mainly summarize the recent advances on the rational design of Cu nanostructures, the composition regulation of Cu-based alloys, and the exploitation of advanced supports for improving the catalytic activity and selectivity toward electrochemical reduction of CO. The special focus is to demonstrate how to enhance the activity and selectivity of Cubased electrocatalyst for COreduction. The perspectives and challenges for the development of Cu-based electrocatalysts are also addressed. We hope this review can provide timely and valuable insights into the design of advanced electrocatalytic materials for COelectrochemical reduction.

Synthesis and Properties of Novel Cationic Maleic Diester Polymerizable Surfactants

Three new cationic polymerizable surfactants are synthesized by the reaction of alkylmaleic hemiester with glycidyltrimethylammonium chloride. Their structures are confirmed by H-1 NMR, IR and elements analysis. The values of CMC and gamma (CMC) of these surfactants have been measured. One can obtain nearly monodisperse polystyrene latex by emulsion polymerization using the polymerizable surfactant.

Well-dispersed SnO2 nanocrystals on N-doped carbon nanowires as efficient electrocatalysts for carbon dioxide reduction

The conversion of carbon dioxide into valuable organic compounds is a highly promising approach to address the energy issues and environmental problems(e.g., global warming). Herein, we presents a facile and efficient method to prepare highly dense and well-dispersed SnO2 nanocrystals on 1 D N-doped carbon nanowires as advanced catalysts for the efficient electroreduction of CO2 to formate. The ultrasmall SnO2 coated on the N-doped carbon nanowires(SnO2@N-CNW) has been synthesized via the simple hydrothermal treatment coupled with a pyrolysis process. The unique structure enables to expose the active tin oxide and also provides the facile pathways for rapid transfer of electron and electrolyte along with the highly porous carbon foam composed with interconnected carbon nanowires. Therefore, SnO2@NCNW electrocatalyst exhibits good durability and high selectivity for formate formation with a Faradaic efficiency of ca. 90%. This work demonstrates a simple method to rationally design high-dense tin oxide nanocrystals on the conductive carbon support as advanced catalysts for CO2 electroreduction.

Surfactant-free oil/water and bicontinuous microemulsion composed of benzene,ethanol and water

Generally,a microemulsion consists of oil,water,surfactant and sometimes cosurfactant.Herein,we report a novel suffactant-free microemulsion（denoted as SFME） composed of benzene,water and ethanol without the amphiphilic molecular structure of traditional surfactant.The phase behavior of the ternary system was investigated,finding that there were a single-phase region and a two-phase region in ternary phase diagram.The electrical conductivity measurement was employed to investigate the microregion of the single-phase region,and a bicontinuous microregion and a benzene-in-water（O/W） microemulsion microregion were identified,which was confirmed by freeze-fracture transmission electron microscopy（FF-TEM） observations.The sizes of the microemulsion droplets are in the range of 20-50 nm.

Small-sized cuprous oxide species on silica boost acrolein formation via selective oxidation of propylene

Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.

Fe- and Co-doped lanthanum oxides catalysts for ammonia decomposition:Structure and catalytic performances

In this paper, a series of Fe- and Co-doped lanthanum（hydr）oxides catalysts were prepared by a simple coprecipitationhydrothermal method. The as-prepared catalysts were characterized with various techniques including powder X-ray diffraction（XRD）, N2 adsorption/desorption, inductively coupled plasma（ICP） and transmission electron microscopy（TEM）. The Fe-based catalysts exhibited consecutive phase changes of amorphous Fe Ox→FeLaO3→Fe2N under different stages（as-prepared→calcination→ammonia decomposition reaction）; as for Co-based catalysts, the phase transformation followed a sequence of Co（OH）2→Co3O4→metallic Co. It was revealed that Fe2N and metallic Co were most probably the active crystalline phase respectively for Feand Co-based catalysts in the decomposition of ammonia.

A flexible solid-state supercapacitor based on graphene/polyaniline paper electrodes

The direct coating of graphene sheets obtained by electrochemical exfoliation on commercial paper renders the preparation of highly conductive flexible paper substrate for subsequent deposition of polyaniline (PANi) nanorods via electrochemical polymerization. The deposit ion of PANi can be well-controlled by adjusting the electrochemical polymerization time, leading to the formation of PANi coated graphene paper (PANi-GP). The as-prepared electrode exhibited high areal capacitance of 176 mF cm^-2 in three-electrode system at a current density of 0.2 mA cm^-2 which is around 10 times larger than that of pris-tine graphene paper due to the pseudocapacitive behavior of PANi. In-situ Raman test was used to determine the molecular changes during redox process of PANi. More importantly, all-solid-state symmetric capacitor assembled with two PANi-GP electrodes in a polymer electrolyte delivered an areal capacitanee of 123 mF cm^-2, corresponding to an areal energy density of 17.1 μWh cm^-2 and an areal power density of 0.25 mW cm^-2. The symmetric capacitor held a capacitive retention of 74.8% after 500 bending tests from 0 to 120°, suggesting the good flexibility and mechanical stability. These results showed the great promising application in flexible energy-storage devices.

The photoluminescence of Co-Al-layered double hydroxide

We report a new optical behaviour of pure Co-Al-layered double hydroxide （LDH）. It was found that the Co-Al-LDH sample could emit fluorescence without any fluorescent substances intercalated. Its excitation spectrum shows a maximum peak near the wavelength 370 nm, the maximum emission peak appears at 430 um and the photoluminescence colour of the Co-Al-LDH sample is blue. This new optical property will be expected to extend the potential applications of LDHs in optical materials field.

Phase behavior and structure analysis of the middle mixed layer for ASP flooding system at low surfactant concentration

The phase behavior and interfacial tension of alkali/surfactant/polymer (ASP) flooding system and simulative crude oil were investigated, and the size distribution and structure analysis of the middle mixed layer (MML) were also studied by size analyzer and freeze-fracture TEM. It was found that there were some rules between the volume of MML and the concentration of each component, and the interfacial tension between MML and the oil phase or water phase could reach an ultra-low value. Especially, the freeze-fracture TEM micrographs of MML were firstly obtained, and the new viewpoint was put forward that there coexist the structures of micelle, microemulsions and emulsions in MML and the structure of microemulsion is dominant. This would make an important effect on the research of surfactant theory and ASP flooding mechanism.

Three-dimensional nitrogen and phosphorous Co-doped graphene aerogel electrocatalysts for efficient oxygen reduction reaction

The development of efficient electrocatalysts for oxygen reduction reaction(ORR) is of importance for fuel cells and metal-air batteries. Herein, three-dimensional nitrogen and phosphorous co-doped graphene aerogel(NPGA) was prepared via the pyrolysis of polyaniline(PANi) coated graphene oxide aerogel synthesized by oxidative polymerization of aniline on graphene oxide(GO) sheets in the presence of phytic acid. The uniform coating of PANi thin layer on the surface of GO sheets enables the formation of highly porous composite aerogel of PANi and GO. The subsequent thermal treatment is able to prepare the porous NPGA due to the carbonization of PANi and phytic acid as nitrogen and phosphorous resources. When used as electrocatalysts,the as-prepared NPGA electrocatalysts exhibited good catalytic activity to ORR via an efficient four-electron pathway with good stability, benefiting from the highly porous structure and the heteroatom co-doping. More importantly, Zn-air batteries operated in ambient air have been fabricated by coupling a Zn plate with the NPGA electrocatalyst in an air electrode, demonstrating the maximal power density as high as ~260 W/g and a good long-term stability with slightly potential decay for over 450 h. The facile method for preparing efficient carbon based ORR electrocatalysts would generate other potential applications including fuel cells and others.

Atomic Bridging of Sn Single Atom with Nitrogen and Oxygen Atoms for the Selective Electrocatalytic Reduction of CO_(2)

The atomic coordination structure of single atom catalysts is crucial in modulating the electrocatalytic reduction of CO_(2)into desirable products.However,there remains limited insight into their roles and catalytic mechanisms.In comparison with commonly proposed metal-N4 moieties,herein the atomic bridging structure of nitrogen-tin-oxygen confined in porous carbon fibers is first presented for the selective reduction of CO_(2).With the detailed identification of such a unique structure,the in situ experimental results and theoretical calculations demonstrate that the bridging structure with reactive oxygen species enables the favorable surface electronic status to form adsorbed intermediate,*COOH for selective CO generation.Typically,the electrocatalyst displays high Faradaic efficiency in reducing CO_(2)into CO,but formate is produced on traditional Sn-based catalysts.Additionally,the solar-driven CO_(2)-H_(2)O system displays a desirable solar-to-CO conversion efficiency of 12.9%.This work provides fundamental guidance for the rational regulation of the atomic coordination structure to improve the production selectivity.

Nitrogen, phosphorus co-doped carbon cloth as self-standing electrode for lithium-iodine batteries

Rechargeable lithium-iodine (Li-I2) battery is a promising energy storage system because of the high energy and power density. However, the shuttle effects of iodine species and the unstable features of l2 block the practical applications of Li-I2 batteries. Herein, a dual heteroatom doped porous carbon cloth is fabricated as the host material for lithium iodide (Lil). Specifically, the self-standing nitrogen, phosphorus co-doped carb on cloth with high Lil loading exhibits a large specific capacity (221 mAh·g^-1 at 1 C), excelle nt rate capability (95.8% capacity rete ntion at 5 C) and superior I ong cycli ng stability (2,000 cycles with a capacity rete ntion of 96%). Electrochemical kin etic an alysis con firms the domi nant contribution of capacitive effects at high sean rates, which is responsible for the good high-rate performance. The improved electrochemical performance mainly stems from two unique features of nitrogen, phosphorus co-doped porous carbon cloth. Heteroatom doping provides extra active sites for strong adsorption of iodine species while the highly porous structure with large surface area favors the capacitive effects at high rates. This work provides a facile yet efficient approach to regulating both redox reaction and capacitive effects via adjusting surface composition and pore structure of carbon materials for en hanced battery performance.

Studies on Y- Potential of Positive Sol of Magnesium Aluminum Hydroxide

The IEP of magnesium aluminum hydroxide was predicted with the modified Yoon′s equation, and the effect of electrolyte on the Y- potential of the sol was studied by electrophoresis method. The results showed that the calculated IEP values with the modified Yoon′s equation agreed well with the experimental ones. With the increase of the ionic radius of monovalent anions (Cl -, Br -, I -) the ζ potential decreased. The same was true for CO 2- 3, SO 2- 4 but the sign of the Y- potential reversed from positive to negative. For Al 3+ , Ca 2+ , Mg 2+ , however, the ζ potential increased with the increase of the concentration of Al 3+ , Ca 2+ , Mg 2+ .

Studies on the Phase Properties of Winsor Ⅰ-Ⅲ Type Microemulsions with Dielectric Relaxation Spectroscopy

The dielectric relaxation spectroscopy （DRS） of Winsor I -Ⅲ microemulsions for nonionic surfactant octyl polyglucoside CsG1.46/1-butanol/cyclohexanedwater system was studied. The experiment shows that the permittivity decreases with the increase in the frequency and clear dielectric relaxation phenomena were observed. Permittivity obviously decreases with the change of the microstructure of the microemulsion, W/O, B.C. and O/W can be distinguished by the permittivity.

In situ embedded bismuth nanoparticles among highly porous carbon fibers for efficient carbon dioxide reduction

Electrocatalysis provides an optimal approach for the conversion of carbon dioxide(CO_(2))into high-value chemicals,thereby presenting a promising avenue toward achieve carbon neutrality.However,addressing the selectivity and stability challenges of metal catalysts in electrolytic reduction remains a daunting task.In this study,the electrospinning method is employed to fabricate porous carbon nanofibers loaded with bismuth nanoparticles with the help of in situ pyrolysis.The porous carbon nanofibers as conductive support would facilitate the dispersion of bismuth active sites while inhibiting their aggregation and promoting the mass transfer,thus enhancing their electrocatalytic activity and stability.Additionally,nitrogen doping induces electron delocalization in bismuth atoms through metal-support interactions,thus enabling efficient adsorption of intermediates for improving selectivity based on the theoretical calculation.Consequently,Bi@PCNF-500 exhibits the exceptional selectivity and stability across a wide range of potential windows.Notably,its faradaic efficiency(FE)of formate reaches 92.7%in H-cell and94.9%in flow cell,respectively,with good electrocatalytic stability.The in situ characterization and theoretical calculations elucidate the plausible reaction mechanism to obtain basic rules for designing efficient electrocatalyst.

Nanoceria Supported Gold Catalysts for CO Oxidation

Two types of CeO2 nanocubes （average size of 5 and 20 nm, respectively） prepared via the hydrothermal process were selected to load gold species via a deposition-precipitation （DP） method. Various measurements, including X-ray diffraction （XRD）, Raman spectra, high resolution transmission electron microscopy （HRTEM）, in situ diffuse reflectance infrared Fourier transform spectroscopy （in situ DRIFTS）, and temperature-programmed reduction by hydrogen （H2-TPR）, were applied to characterize the catalysts. It is found that the sample with ceria size of 20 nm （Au/CeO2-20） was covered by well dis ersed both Au^3＋ and Au^δ＋ （0〈δ〈1）. For the other sample with ceria size of 5 nm （Au/CEO2-5）, Au^3＋ is the dominant gold species. Au/CeO2-20 performed better catalytic activity for CO oxidation because of the strong CO adsorption of Au^δ＋ in the catalysts. The catalytic activity of Au/CeO2-5 was improved due to the transformation of Au^3＋ to Au^δ＋. Based on the CO oxidation and in situ DRIFTS results, Au^δ＋ is likely to play a more important role in catalyzing CO oxidation reaction.