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To solve environmental pollution and energy crisis, it is essential to design an efficient, economical, and stable bifunctional electrocatalyst for water splitting to produce renewable energy sources H

Lithium-sulfur (Li-S) batteries are regarded as one of the promising candidates for the next-generation energy storage system owing to their high capacity and energy density. However, the durable operation for the batteries is blocked by the shuttle behavior of soluble lithium polysulfides and the sluggish kinetics in the redox process. Here, VN nanoparticles on nitrogen-doped graphene (VN/NG) composite is synthesized by simple calcining method to modify the separators, which can not only chemically trap polysulfides, but also catalyze the conversion reaction between the polysulfides and the insoluble Li2S during the charge/discharge process. The catalytic effects of VN/NG are verified by the calculated activation energy (Ea), which is smaller than the counterpart with NG toward both directions of redox. Because of the synergistic adsorption-catalysis of VN/NG, the cells with VN/NG-modified separators deliver a superior rate performance (791 mAh g−1 at 5C) and cycling stability (863 mAh g−1 after 300 cycles with a low decaying rate of 0.068% per loop at 1C). This work provides a simple preparation strategy and fundamental understanding of the bifunctional catalyst for high-performance Li-S batteries.

China’s energy structure mainly depends on coal resources, which will still play the dominant role in economic development in the future. With the mining depth increasing, the deep roadway construction will be exposed to a complex stress environment, increasing the difficulty of roof control and further hindering the mining activities. The problem of deep roadway excavation causing significant fracture scope of surrounding rock in and outside the anchorage zone has attracted much attention. For the large crack scope existing in the roadway roof of deep underground openings, this paper focuses on the exploration of upgrading the support system. In order to solve this problem, we investigated the zone damage of the roadway roof with the discrete element model using the UDEC trigon method and damage quantified evaluation with data analysis. The long anchorage and zone linkage support technology was proposed based on the damage control effect of varying lengths of supporting bolts. The purpose of extending the length of bolts is to link the more severely damaged rock mass in the shallow part to the minimum damaged part in the deep place, aiming to form the thick anchor zone to mobilize the rock mass in each zone to participate and bear the load together. Furthermore, the onsite application of long anchorage and zone linkage technology gained good control effects in the selected typical roadway with different geological conditions. The results show obvious resistance in cross-section shrinkage, integrity maintenance, and minimization of crack scope in the roadway roof. The promotion of long anchorage zone linkage technology can help the mine with similar situations uplift the efficiency of working and guarantee the safety of miners during mine service life in the deep coal roadway.

Carbon-supported Co–Au bimetallic nanoparticles with different Co/Au atomic ratios were prepared through two-step reduction in a reverse microemulsion system. The prepared catalysts were investigated as anode electrocatalysts for the electrooxidation of borohydride through X-ray diffractomer, transmission electron microscopy, cyclic voltammetry, chronoamperometry, chronopotentiometry, electrochemical impedance spectroscopy (EIS), and fuel cell test. Results showed that the Co4–Au1/C catalyst presents the highest catalytic activity and the lowest electrochemical impedance for BH4− electro-oxidation with the electron-transfer number of 4.1 among all the resultant catalysts. In addition, a laboratory direct borohydride-hydrogen peroxide fuel cell (DBHFC) with Co4–Au1/C anode obtains the maximum power density as high as 102.4 mW cm−2, which was 2.14 times that obtained when Au/C catalyst was used. All these results are indicating that the Co4–Au1/C is an efficient anode catalyst for direct borohydride-hydrogen peroxide fuel cell.

A freestanding thin-film composite with carbon nanotubes/carbon fiber modified by sulfur (S-CNTs/CF) has been fabricated by chemical vapor deposition (CVD) method as the binder-free cathode for lithium sulfur battery. This porous electronic conductor with 3D structure improved the electrochemical performance of the cathodes by simultaneously increasing porosity of material and changing conductive pathway. Electrochemical test results showed that the discharge specific capacity of S-CNTs/CF positive electrode decreased slightly from initial 1213.6 mAh g−1(Sulfur) to 798.4 mAh g−1(Sulfur) after 55 cycles. Comparing with powder cathode, the electrochemical performance of S-CNTs/CF cell is improved significantly. It proves that establishing a sulfur electrode with stable conductive and high porous structure provide a promising way to improve the cycle life.

In this work, a novel g-C3N4 modified Mn3O4 composite was synthesized and applied to activate peroxymonosulfate (PMS) for phenol degradation under simulated sunlight. We investigated the effect of solution initial pH and reaction temperature, meanwhile ascertaining the optimal molar ratio of Mn3O4 and g-C3N4 and the stability and reusability of the materials. The g-C3N4/Mn3O4 exhibited superior activity for PMS activation under simulated sunlight, 87.3% phenol degradation and 47.3% phenol mineralization at 60 min were achieved. The combination of Mn3O4 nanoparticles and g-C3N4 sheets results in a higher catalytic activity than pure Mn3O4 and g-C3N4. Furthermore, quenching experiments and electron spin resonance measurements (ESR) prove that phenol degradation by g-C3N4/Mn3O4/PMS system is primarily attributed to the generation of sulfate radicals, hydroxyl radicals, and superoxide radicals. A possible mechanism was proposed for phenol removal by g-C3N4/Mn3O4/PMS system under simulated sunlight. This work is intent to arise more interest about solar light for PMS activation and future research on water treatment.

In this study, amorphous NiB alloy decorated by Cu is prepared by chemical reduction. Moreover, the effect of Cu addition for the electrocatalytic activity of borohydride (BH4−) oxidation is studied. The physical characteristics of NiB or NiBCux nanoparticles are confirmed by transmission X-ray diffraction (XRD) and scanning electron microscopy (SEM). The physical characterization results demonstrate that the NiB or NiBCux nanoparticles have an amorphous structure and NiBCux nanoparticles have improved dispersity. The borohydride oxidation activity of the as-prepared catalysts is investigated by cyclic voltammetry (CV), linear scan voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results indicate that the NiBCux/C nanoparticles have higher electrocatalytic activity for borohydride oxidation than NiB/C, and the borohydride oxidation current of NiBCux/C nanoparticles initially increases and then decreases with the increase in Cu content. The optimum molar content of copper in the six prepared catalysts is 2.2%. It is proposed that the addition of Cu is conducive to sodium borohydride adsorption, thereby improving the electro-oxidation activity for borohydride. Hence, amorphous NiB alloy decorated by Cu can enhance the electro-oxidation performance for borohydride.

Highly efficient visible-light-driven Pt-decorated g-C3N4/Bi2WO6 hybrid photocatalysts were successfully prepared via a photodeposition method. The microstructures and optical properties of the prepared samples were characterized by transient photocurrent experiments, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis diffused reflectance spectra (DRS), photoluminescence (PL), electron spin resonance (ESR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. FESEM and TEM images show that metallic Pt particles disperse on the surface of g-C3N4/Bi2WO6 hybrid. Pt-decorated g-C3N4/Bi2WO6 compsites exhibited excellent DRS attribute to the surface plasmonic resonance (SPR) of Pt particles and g-C3N4/Bi2WO6. The PL results verified that the suitable band potential of g-C3N4 and Bi2WO6 for construction of Z-type photocatalytic system. In the photocatalytic experiment, results showed that Pt(1%)-g-C3N4/Bi2WO6 photocatalysts displayed higher photocatalytic activity than either pure g-C3N4 or Bi2WO6 for the degradation of Rhodamine B (RhB). Additionally, the free-radical trapping experiments and ESR disclose that the hole (h+), superoxide radical ( O2−) and hydroxyl radical (·OH) acted as reactive species. Based on above, a possible plasmonic Z-scheme mechanism for organics degradation over Pt-decorated g-C3N4/Bi2WO6 was proposed.

The electrochemical reduction of CO2 to methanol is a promising strategy, which currently suffers from the poor catalytic activity, selectivity, and stability of the electrode. Here, we report a simple one-pot hydrothermal strategy to fabricate Mo&ndash, Bi BMC@CNT nanocomposites, in which Mo&ndash, Bi bimetallic chalcogenide nanoparticles were in-situ decorated on carbon nanotubes. The Mo&ndash, Bi BMC nanoparticles with an average particle size of 12 nm were uniformly supported on the surface of CNTs without aggregation into larger clusters. The Mo&ndash, Bi BMC@CNT nanocomposites exhibited a relatively good catalytic performance for the electrochemical reduction of CO2 to methanol in a 60 wt.% 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous electrolyte. Among them, the Mo&ndash, Bi BMC@CNT-15% nanocomposite showed the highest Faradaic efficiency of 81% for methanol at &minus, 0.3 V vs. a saturated calomel reference electrode (SCE) and a stable current density is 5.6 mA cm&minus, 2 after a run time of 12 h. The excellent catalytic properties are likely attributed to its nanostructure and fast electron transfer. These derive from the synergistic effect of Mo&ndash, Bi and the high conductivity of CNTs. This work opens a way to provide an efficient catalytic system for the electroreduction of CO2 to methanol in industrial applications.

Owing to their high theoretical capacity and low material cost, lithium-sulfur batteries (LSBs) are considered the most promising next-generation energy storage devices. In response to existing LSBs problems, facilitating the conversion of lithium polysulfides (LiPSs) is considered an effective method, and the LiPSs conversion in the liquid phase provides the majority of the capacity of LSBs. Understanding the kinetics of redox processes of LiPSs in liquid-electrolyte LSBs is crucial. In this study, we have designed a new flowing electrolyte three-electrode system, equipped with a tiny H-type electrolytic cell isolated using the Nafion membrane, to quantitatively measure the intrinsic kinetics of LiPSs conversion. As a result, the onset redox potentials, exchange current densities, reaction orders, and apparent activation energy of the LiPSs conversion were obtained on the basis of the steady-state polarization curves. The onset reduction potentials of main LiPSs were 2.427, 2.348, 2.281, 2.212, and 2.139 V (vs Li+/Li) for S8, Li2S8, Li2S6, Li2S4, and Li2S2, respectively. The calculated exchange current density of Li2S6 redox was the highest (188.55 µA/cm2), while the S8 reduction was the minimal (0.97 µA/cm2). In addition, the reaction orders and apparent activation energies of Li2S8, Li2S6, Li2S4 were studied. The kinetic parameters obtained were related to the formation of the potential plateaus and the sloping regions, especially for the exchange current densities associated with LSBs charge/discharge process. These parameters were used to decipher the charge/discharge curves and CV profile of S8 in detail. This study could assist in understanding of the LSBs reaction mechanism.

In this paper, amorphous Ni-B nanoparticles doped with cobalt are successfully prepared by simple chemical reduction to investigate the mechanism by which cobalt enhances the electroactivity. Transmission electron microscopy (TEM) images indicate that the morphology of the Ni-B-(Co) amorphous nanoparticles is uniformly spherical, and that the particle size is about 10–15 nm. X-ray photoelectron spectra (XPS) show that Co electrons shifted to B and Ni. Subsequently, the electrocatalytic characteristics were investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The results show that the methanol electro-oxidation current of Ni-B-(Co) amorphous nanoparticles initially increased and decreased as the Co content increased. Ni-B-Co0.05 nanoparticles exhibited the best electrocatalytic activity for methanol oxidation. It is proposed that the role of cobalt in methanol catalysis on the surface of amorphous Ni-B-Co nanoparticles is initially to promote the generation of NiOOH by preferentially forming CoOOH. Meanwhile Co could increase the absorption ability of Ni 3d orbit toward the methanol and intermediates, and thus improve the catalytic activity toward methanol. Our study provides a theoretical guide concerning doped atoms raising the electroactivity of the methanol oxidation on amorphous Ni-B nanoparticles.

Carbon-supported Au–Ni–Cu, Au–Ni, Au–Cu and Au nanoparticles were synthesised using a polyol reduction method. The prepared nanoparticle catalysts were used as anode electrocatalysts in direct borohydride–hydrogen peroxide fuel cells. The physical properties of the as-prepared electrocatalysts were studied using X-ray diffraction (XRD), and transmission electron microscopy (TEM). XRD and TEM analyses showed that the average size of the particles was approximately 10–20 nm. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were employed to analyse the borohydride oxidation reaction (BOR) on Au/C, Au–Cu/C, Au–Ni/C and Au–Ni–Cu/C. The results showed that the catalytic activity for BOR decreased in the order Au2–Ni1–Cu1/C > Au1.5–Ni1–Cu1/C > Au1–Ni1/C > Au1–Cu1/C > Au/C. Single-cell direct borohydride fuel cell (DBFC) tests also attested that the Au2–Ni1–Cu1/C anode catalyst exhibited better performance than the Au–Cu/C, Au–Ni/C and Au/C anode catalysts. Therefore, the ternary Au2–Ni1–Cu1/C catalyst can be a potential anode catalyst for DBFCs.

A metastable hexagonal WO3 (h-WO3) was prepared by a hydrothermal reduction method with glycerol and the Ag3PO4/h-WO3 composites were synthesized via a precipitation method. Several techniques were employed to characterize the Ag3PO4/h-WO3 composites. Compared to the Ag3PO4/WO3 photocatalysts, the Ag3PO4/h-WO3 photocatalysts exhibited an excellent visible light photocatalytic performance for efficient degradation of methyl orange (MO). The analysis results showed that the favorable photocatalytic performance of the Ag3PO4/h-WO3 composites were mainly attributed to the h+ and O2− generated during the recycles of W6+ and W5+. Furthermore, under the same conditions, the Ag3PO4/h-WO3 composites showed better stability than pure Ag3PO4 photocatalyst for degradation of MO, indicating that h-WO3 played an important role in the process of degradation. Based on the results of trapping experiments and XPS characterization analysis, the photocatalytic mechanism of the Ag3PO4/h-WO3 composites were proposed.

The commercialization of lithium-sulfur (Li-S) batteries is severely plagued by the shuttle effect and sluggish kinetic conversion of polysulfides. Herein, the layered cobalt phosphide CoP/C nanoparticle derived from MOF-71 by two-step heat treatment was synthesized to act as sulfur host in Li-S batteries. The physical characterization results indicate that Co-CoP/C has a specific surface area of 113 m2 g−1, with more micropores and mesopores, which is beneficial to the transmission of ions and electrons. MOF-derived polar metal phosphide Co-CoP/C has shown layered porous structure, which can provide more the active site to adsorb more polysulfides, furthermore, the cobalt phosphide can promote catalytic conversion of polysulfides. Thus the lithium-sulfur battery assembled with Co-CoP/C@S as the positive electrode showed excellent electrochemical performance: tested at a rate of 0.2 C, the initial discharge specific capacity of the battery reached 1441.9 mAh g−1. Additionally, the long-cycle stability performance test was performed at a rate of 0.5 C, and the battery still maintained a reversible specific capacity above 600 mAh g−1 after 300 cycles of charge and discharge.

Given the scarcity and high cost of metal Pt, the search for cheap and readily available non-precious metal catalysts remains the key to solving hydrogen evolution reactions (HER) today. Transition-metal phosphides (TMPs) have been widely studied in recent years due to their excellent catalytic activity. In this work, we using Co-based metal-organic framework (MOF) as the precursor, prepared two kinds of cobalt phosphide (CoP/C) by direct phosphating and indirect phosphating methods, which showed good electrochemical performance of HER. The Di-CoP/C showed lower overpotential of 136 mV at 10 mA cm−2 in the acid electrolyte, and the slope of Tafel was 49.3 mV dec−1. At the same time, the catalyst showed excellent stability.

Novel nitrogen-doped carbon quantum dots/Ag 3 PO 4 (NCQDs/Ag 3 PO 4 ) complex photocatalysts were synthesized by a facile precipitation method at room temperature. The physical and chemical properties of Ag 3 PO 4 and NCQDs/Ag 3 PO 4 photocatalysts were detected through X-ray powder diffraction, field emission scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and electron spin resonance techniques. The as-prepared 3-NCQDs/Ag 3 PO 4 composite exhibited much higher activity than the pure Ag 3 PO 4 for eliminating methyl orange and bisphenol A solution under visible light (λ > 420 nm). Moreover, in the cyclic experiments, the 3-NCQDs/Ag 3 PO 4 exhibited an excellent stability for the decolorization of methyl orange at some level. This suggested that NCQDs played an important role in the process of degradation. The function of NCQDs was discussed and a new mechanism was put forward for the degradation of methyl orange. The high activities and stability were attributed to the transfer of photogenerated charges through the vector of Ag 3 PO 4 → NCQDs → Ag in the photocatalytic process, leading to effective charge separation of Ag 3 PO 4 .

A series of new hydroxypyridine-based ionic liquids (ILs) are synthesized and applied in CO2 capture through chemical absorption, in which one IL, i.e., tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]), shows a viscosity as low as 193 cP with an absorption capacity as high as 1.20 mol CO2 per mol IL. Because the traditional anion–CO2 absorption mechanism cannot provide an explanation for the influences of cations and temperature on CO2 absorption capacity, herein, a novel cation-participating absorption mechanism based on the proton transfer is proposed to explain the high absorption capacity and the existence of a turning point of absorption capacity with the increase of temperature for the capture of CO2 using [P4444][n-Op] (n = 2, 3, 4) ILs. Also, the relationship between the viscosity of ILs and the linear interaction energy is proposed for the first time, which can guide how to design and synthesize ILs with low viscosity. Quantum chemistry calculations, which are based on the comprehensive analysis of dipole moment, cation–anion interaction energy and surface electrostatic potential, indicate that the different viscosities of hydroxypyridine-based ILs and the changes after CO2 absorption mainly resulted from the different distribution of negative charges in the anion.

To achieve low cost, high rate and attractive capacity of CO2 adsorption by using ionic liquid (IL), new mesostructured ionogel, pyridine-containing anion functionalized IL tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]) encapsulated silica MCM-41 (noted as PM-w), is fabricated by loading the newly designed IL [P4444][2-Op] with multiple active sites into porous silica MCM-41 through a simple moisture-controlled impregnation-evaporation method. Allosteric effect driven gas sorption on the electronegative oxygen and nitrogen atoms of the nanoconfined IL [P4444][2-Op] makes it take no more than 2 min for the ionogel PM-5 to achieve the 90% of saturated adsorption capacity. Corresponding adsorption rate is 30 times faster than that of the bulk IL. The ionogel PM-5 with the low IL loading of 5% shows the highest CO2 adsorption capacity up to 1.21 mmol·(g-Ionogel)-1 (14.89 mmol·(g-IL)-1) at 50 °C in a gas mixture with N2, which is 9.25 times higher than that of the pure IL. Its excellent cyclic stability of more than 96% of the initial CO2 uptake repeatedly displayed after performing 10 cycles of adsorption-desorption tests. The enhanced thermal stability up to 450 °C in N2 is observed for the low loading ionogels since the strong interfacial layering of the IL preferring to dot the silica nanopores as monomolecular islands. Reversely, the high loading IL may aggregate into nanosized clusters that recover the poor thermal stability of the bulk IL. Reasonable decreasing in their surface area, pore volume and pore size are observed with the IL loading up to 45%. They still exhibit highly ordered hexagonal mesostructure. Featuring with low loading and cost, rapid adsorption, high capacity and excellent cyclic stability make the ionogel PM-5 a competitive candidate in CO2 capture from the flue gas.

Despite an increased interest in sustainable energy conversion systems, there have been limited studies investigating the electrocatalytic reaction mechanism of methanol oxidation on Ni-based amorphous materials in alkaline media. A thorough understanding of such mechanisms would aid in the development of amorphous catalytic materials for methanol oxidation reactions. In the present work, amorphous Ni-B and Ni-B-Co nanoparticles were prepared by a simple chemical reduction, and their electrocatalytic properties were investigated by cyclic voltammetry measurements. The diffusion coefficients (D0) for Ni-B, Ni-B-Co0.02, Ni-B-Co0.05, and Ni-B-Co0.1 nanoparticles were calculated to be 1.28 &times, 10&minus, 9, 2.35 &times, 9, 4.48 &times, 9 and 2.67 &times, 9 cm2 s&minus, 1, respectively. The reaction order of methanol in the studied transformation was approximately 0.5 for all studied catalysts, whereas the reaction order of the hydroxide ion was nearly 1. The activation energy (Ea) values of the reaction were also calculated for the Ni-B and Ni-B-Co nanoparticle systems. Based on our kinetic studies, a mechanism for the methanol oxidation reaction was proposed which involved formation of an electrocatalytic layer on the surface of amorphous Ni&ndash, B and Ni-B-Co nanoparticles. And methanol and hydroxide ions could diffuse freely through this three-dimensional porous conductive layer.

A h-WO3 decorated Ag–AgCl composite was prepared through facile precipitation and photoreduction methods and demonstrated to be a highly efficient and stable photocatalyst for the degradation of Rhodamine B (RhB) under visible light. Ag–AgCl/h-WO3 exhibited much improved photocatalytic performance was elucidated from the physical–chemical properties of AgCl and h-WO3 and the surface plasmon resonance effect of the Ag particles. The techniques of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectrometry (XPS) and photocurrent were used to characterize crystalline phases, morphology, composition and separation efficiency between electrons (e−) and holes (h+) of the synthesized composite photocatalyst. XPS results confirmed the existence of W5+ and W6+ on the surface of h-WO3 sample, which favored electrons transfer between AgCl and Ag, and generated superoxide radical for the degradation of RhB. The active species trapping experiments results further demonstrated that the formation of superoxide radical during the system. Finally, the underlying photocatalytic mechanism for the removal of RhB by Ag–AgCl/h-WO3 composite was examined.

The shuttle effect of soluble intermediate polysulfide toward lithium anode, the sluggish redox kinetics of polysulfides conversion and the low lithium ion/electrical conductivity severely limited the commercialization of lithium-sulfur (Li-S) battery. To overcome the bottleneck, herein we designed a Nickel foam/graphene/sulfonated carbon nanotubes (NG/CNTs-SO3−) three-dimensional (3D) interconnected electrode. Nickel foam weaved with 1D multi-wall carbon nanotubes (MWCNT) and 2D graphene (named as NG/CNTs) is used as the host for sulfur accommodation, forming a continuously ion-electronic conductive 3D network and boosting fast redox reaction kinetic. Moreover, the negatively charged –SO3− groups transform the cathode surface from hydrophobic to hydrophilic, and it not only acts as constructing ion-selective layer for suppressing the shuttle effect of polysulfides, but also accelerates the polysulfides conversion process by strong adsorption sites to anchor polysulfides. In addition, the grafted –SO3− groups reinforce the rapid transportation of lithium-ion five times than none negatively charged groups decorated ones. The Li-S batteries with NG/CNTs-SO3− cathode delivers an initial capacity of 1380 mAh g−1 at 0.2 C, retaining a capacity of 1043.5 mAh g−1 after 100 cycles. Furthermore, the cells with NG/CNTs-SO3− cathode also exhibits excellent cycling stability with capacity decay of 0.031% at 2 C and rate capability, which confirms it is outstanding to improve the electrochemical performance and inhibit the shuttle effect.

Many studies have shown that sulfur electrodes in room-temperature sodium–sulfur (RT Na–S) batteries undergo a liquid-phase electrochemical reaction. Moreover, the electrochemical redox kinetic behavior of S8 and sodium polysulfides (Na2S8, Na2S6, Na2S4, and Na2S2) is important in understanding the macroscopic kinetics of sulfur electrodes. In this study, a three-electrode electrochemical test system is built using a two-chamber micro-electrolysis cell with a flowing electrolyte and Nafion membrane. Electrochemical kinetic parameters, such as the onset redox potentials, exchange current densities, reaction orders, and apparent activation energies of the sodium polysulfides during the redox process are obtained from a steady-state polarization curve. The onset redox potentials of S8, Na2S8, Na2S6, Na2S4, and Na2S2 on Vulcan XC-72R carbon are 2.37, 2.23, 2.11, 1.99, and 1.83 V (vs. Na/Na+), respectively. Furthermore, the relationship between the discharge capacity of sodium polysulfides and their onset redox potentials is established. The aforementioned kinetic parameters are vital in elucidating the formation of discharge/charge platforms and sloping regions in an RT Na–S battery. The results of this work provide a basis to further understand the performance of RT Na–S batteries.

Pyrrolidinium-based ionic liquids (ILs), such as PYR 13 TFSI, PYR 14 TFSI, and PYR 1(2O1) TFSI, exhibit high thermal and electrochemical stability with wide electrochemical windows as electrolytes for application to rechargeable Li–O 2 batteries. In this work, several fundamental properties of three ILs are measured: the ionic conductivity, oxygen solubility, and oxygen diffusion coefficient. The oxygen electro-reduction kinetics is characterized using cyclic voltammetry. The performances of Li–O 2 batteries with these IL electrolytes are also investigated using electrochemical impedance spectroscopy and galvanostatic discharge–charge tests. The results demonstrate that the PYR 1(2O1) TFSI electrolyte battery has a higher first-discharge voltage than the PYR 13 TFSI electrolyte and PYR 14 TFSI electrolyte batteries. Both PYR 13 TFSI- and PYR 1(2O1) TFSI-based batteries exhibit higher first-discharge capacities and better cycling stabilities than the PYR 14 TFSI-based battery for 30 cycles. A theoretical analysis of the experimental results shows that the diffusion coefficient and solubility of oxygen in the electrolyte remarkably affect the discharge capacity and cycling stability of the batteries. Particularly, the oxygen diffusion coefficient of the IL electrolyte can effectively facilitate the electrochemical oxygen electro-reduction reaction and oxygen concentration distribution in the catalyst layers of air electrodes. The oxygen diffusion coefficient and oxygen solubility improvements of IL electrolytes can enhance the discharge–charge performances of Li–O 2 batteries.

Carbon-supported Ni@Ag core-shell nanoparticles were synthesized and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The morphology, structure, and composition of the as-prepared electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Electrochemical characterizations are performed by cyclic voltammetry (CV), chronoamperometry (CA), linear scan voltammetry with rotating disk electrode (LSV RDE), and fuel cell test. The catalytic behaviors and main kinetic parameters (e.g., Tafel slope, number of electrons exchanged, exchange current density, and apparent activation energy) toward BH 4 ‐ oxidation on Ag/C and Ni@Ag/C electrocatalysts are determined. Results show that the as-prepared nanoparticles have a core-shell structure with the average size approximately 13 nm. The kinetics of NaBH4 oxidation is faster for Ni@Ag/C than that for Ag/C. Among the as-prepared catalysts, the highest transition electron value and the lowest apparent activation energy are obtained on Ni1@Ag1/C; the values are 4.8 and 20.23 kJ mol−1, respectively. The DBHFC using Ni1@Ag1/C as anode electrocatalyst and Pt mesh (1 cm2) as cathode electrode obtains the maximum anodic power density as high as 8.54 mW cm−2 at a discharge current density of 8.42 mA cm−2 at 25 °C.

Carbon supported Cu-Ag (Cu-Ag/C) bimetallic nanoparticles prepared by the impregnation reduction method in aqueous solution are evaluated as anode catalysts for sodium borohydride (NaBH 4 ) oxidation. The physical properties of the as-prepared electrocatalysts are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM). Electrochemical oxidation of NaBH 4 at carbon-supported Ag/C and Cu-Ag/C is studied in 2 M NaOH/0.1 M NaBH 4 using linear scan voltammetry with rotating disc electrode (LSV RDE), chronoamperometry (CA) and in situ Fourier transform infrared spectroscopy (in situ FTIR). Main kinetic parameters (e.g. Tafel slope, apparent rate constant, number of electrons exchanged, and exchange current density) for NaBH 4 oxidation on these electrocatalysts are determined. Results show that the average size of the Cu-Ag/C particles is approximately 14 nm. The kinetic parameters for the NaBH 4 oxidation are better for Cu-Ag/C than for Ag/C. Among all the as-prepared catalysts, the Cu 67 Ag 33 /C catalyst presents the highest catalytic activity.

This study demonstrates the preparation of well aligned-carbon nanotube (WA-CNT) arrays onto a carbon paper substrate with a conductive carbon-black layer by the catalyst seed-impregnated chemical vapor deposition method. The prepared WA-CNT arrays were then characterized by scanning electron microscopy for different growth temperatures, standard linear velocities of feed vapors, and ferrocene-to-xylene ratios in the feed vapors. Results indicate that the optimal WA-CNT arrays of length 40–50 μm and diameter 30–40 nm were obtained at the growth temperature range of 750–800 °C, standard linear velocity of 1.40 cm s −1 , and ferrocene-to-xylene molar ratio of 1:50–1:30. These results provide new insights into the growth mechanism of CNT arrays, which involves cross-coupling of chemical reaction and mass transfer based on reaction engineering theory. The samples prepared in the study can be used as catalyst supports in air electrodes considering their three-dimensional porous structure, approximately linear channel, controllable length and diameter distribution, and excellent CNT conductivity. Electrochemical measurement indicated that the WA-CNT arrays/carbon-black layer/carbon paper substrate composites achieved relatively high discharge capacity of 2930 mAh g −1 (CNTs) at a current density of 0.05 mA cm −2 in Li–air batteries, which far exceeded other carbonaceous materials in Li–air batteries.

In this communication, an easy, two-step hydrothermal synthetic protocol for the preparation of hybrid cobalt phosphate/graphite felt (Co3(PO4)2@GF) electrocatalyst is described, where Co3(PO4)2·4H2O is precipitated onto a 3D self-supporting graphite felt (GF). The prepared electrocatalyst, denoted hereafter as GF-Co-P, showed an onset overpotential at 370 mV for the oxygen evolution reaction (OER), which is superior to that of the standard reference material RuO2; and a Tafel slope of 133 mV dec−1 in a pH-neutral phosphate buffer solution (PBS). In addition, it exhibited excellent catalytic stability over extended run times. We revealed that surface phosphorylation greatly enhances the exposure of active cobalt sites at catalyst surfaces, and therefore promotes the charge transfer process for OER in neutral solution.

Carbon-supported Cu@Ag core–shell nanoparticles are prepared by a successive reduction method in an aqueous solution and are used as an anode electrocatalyst for the direct borohydride–hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronopotentiometry (CP), and fuel cell tests. In situ Fourier transform infrared (FTIR) spectroscopy is employed in 2 M NaOH/0.1 M NaBH4 to understand the borohydride oxidation reaction (BOR) mechanism by studying the intermediate reactions occurring on the Cu@Ag/C electrode. The TEM images show that the average size of the Cu1@Ag1/C particles is approximately 18 nm. Among the as-prepared catalysts, the Cu2@Ag1/C catalyst presents the highest catalytic activity. As shown by in situ FTIR, the oxidation reaction mechanism of B H 4 − is similar to that of Ag/C: B H n ( OH) 4−n − + 2O H − → B H n−1 ( OH) 5−n − + H 2 O + 2e . At 25 °C, the DBHFC with Cu2@Ag1/C as the anode electrocatalyst and Pt mesh (1 cm2) as the cathode electrode exhibits a maximum anodic power density of 17.27 mW mg−1 at a discharge current density of 27.8 mA mg−1.

The α-MnO2 nanorod catalysts are prepared by chemical precipitation method, the morphology and crystal configuration are evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the electrolyte salt such as tetrabutylammonium perchlorate/dimethyl sulfoxide (TBAClO4/DMSO) and Lithium bis (trifluoromethanesulfonyl) imide/dimethyl sulfoxide (LiTFSI/DMSO), the reaction mechanism and the products of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) process on glassy carbon electrode, Au electrode and α-MnO2 electrode are analyzed by cyclic voltammetry. In addition electrochemical quartz crystal microbalance (EQCM) are used to measure the mass change on electrode in cyclic voltammetry scan. In LiTFSI/DMSO system, the results show that the ORR reaction mechanism, species and distribution of products on different electrodes are not exactly identical, α-MnO2 nanorod catalysts have good catalytic activity and greatly enhance the reaction kinetics of ORR and OER process.

Carbon supported Cu-Pd bimetallic nanoparticles were prepared by a successive reduction method in aqueous solution and used as anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronopotentiometry (CP), linear sweep voltammetry (LSV) and fuel cell test. The results show that the size of the crystallite is around 12.5 nm, the Cu 1 Pd 1 /C catalyst presents the highest catalytic activity among all the resultant catalysts, and the DBHFC using Cu 1 Pd 1 /C as anode catalyst and Pt mesh (1 cm × 1 cm) as cathode electrode obtains the maximum power density as high as 39.8 mW cm -2 at a discharge current density of 80.1 mA cm -2 at 20 °C.

Carbon-supported Ni–Au nanoparticles with a core–shell structure (Ni@Au/C) are prepared by a combination of reverse microemulsion and two-step reduction. The prepared Ni@Au/C nanoparticles are used as anode electrocatalysts in direct borohydride-hydrogen peroxide fuel cells (DBHFCs). The physical and electrochemical properties of the as-prepared catalysts are investigated using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical quartz crystal microbalance (EQCM), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The average size of the particles are approximately 10 nm. Among the resultant catalysts obtained in this study, the Ni1@Au1/C catalyst exhibits the highest catalytic activity for the direct electro-oxidation of borohydride. DBHFCs fabricated using Ni1@Au1/C as an anode catalyst and Pt mesh (1 cm × 1 cm) as a cathode electrode achieves a maximum power density of 74 mW cm−2 with a discharge current density of 130 mA cm−2 at 20 °C.

Ni@Pt core–shell nanoparticles with Pt nanocrystal thin film are synthesized by chemical reduction to investigate methanol oxidation. The morphology, structure, and composition of the as-prepared nanoparticles are characterized by aberration-corrected high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical characterizations are performed by cyclic voltammetry, in situ Fourier transform infrared spectroscopy, and chronoamperometry. Results show that the as-prepared nanoparticles have a core–shell nanostructure. Moreover, Pt on the shell is composed of small clusters that are poorly crystalline domains of different crystal faces. The Pt mass activity of the as-prepared nanoparticles is about three times that of conventional E-TEK 40 wt% Pt/C catalysts, and methanol oxidation over the as-prepared nanoparticles is found to occur at a lower overpotential than over Pt/C. The as-prepared nanoparticles also exhibit markedly high resistance to carbon monoxide deactivation. This high electrocatalytic performance can be attributed to the unique structure of the as-prepared nanoparticles.