Search

Despite significant progress, precise control of the dispersion of ruthenium (Ru) nanoparticles (NPs) on the carrier, reduction of their aggregation and leaching during water splitting is always a challenging issue. In this work, metal-organic frameworks (MOFs) derived Co 7 Fe 3 alloy/Co NPs embedded in nitrogen-doped carbon and nitrogen-doped carbon nanotubes (FeCoSG/NCNT) with a three-dimensional (3D) spider-egg structure are synthesized by chemical vapor deposition (CVD) technique. Then, Ru NPs are uniformly loaded on the FeCoSG/NCNT through impregnation and reduction. The obtained FeCoSG/NCNT@Ru possesses enriched mesopore and high conductivity. In addition, the Ru NPs synergize with non-precious metal active sites to promote hydrogen-evolution-reaction (HER), which lowers the need for precious metals while maintaining excellent performance. The obtained FeCoSG/NCNT@Ru only requires a low overpotential of 21.1 mV to attain a current density of 10 mA cm−2 in 1 M KOH towards HER, which is smaller than the benchmark catalyst Pt/C (∼30.1 mV). Moreover, it shows ultra-high stability, which can work continuously at current densities of 10, 20, and 30 mA cm−2 for 25 h without degradation, respectively. The study presents insight on the design of advanced support and the construction of highly active and durable electrocatalysts. [Display omitted] • Co 7 Fe 3 alloy/Co NPs embedded in MOF-derived NC encapsulated by NCNT. • The N doping brings a favorable effect on the regulation of Ru distribution. • The unique spider-egg structure provides an abundance of Ru attachment sites. • FeCoSG/NCNT@Ru is a highly efficient and stability HER catalyst. • It exhibits an extremely small overpotential of 21.1 mV at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Abstract Development of advanced electrocatalysts to drive efficient hydrogen evolution reaction through water splitting is vital in many energy related technologies. Herein the development of nitrogen-doped carbon supported fewer-layer MoSe 2 (FL-MoSe 2 /NC) through calcining the hydrothermal product of the Se and Mo precursors in the presence of ammonium citrate is reported. This FL-MoSe 2 /NC is highly efficient for the hydrogen evolution reaction (HER) and exhibits a remarkably low onset potential of 15.2 mV, an extremely small overpotential of 74.6 mV (vs. RHE) at 10 mA cm−2, a greatly reduced Tafel slope of 45.2 mV dec−1, and a higher exchange current density of 0.266 mA cm−2. The performance of the FL-MoSe 2 /NC is much higher than that of most Mo-based HER electrocatalysts reported to date and even comparable to that of other most active non-precious metal based catalysts, suggesting the great potential of using the FL-MoSe 2 /NC as an efficient catalyst for the HER. The NC is believed to play an important role in the high performance of the FL-MoSe 2 /NC. It does not only promote a strong interaction between MoSe 2 and the NC, but facilitates the formation of MoSe 2 with few layers and shorter lattice fringe lengths, which expose more active sites accessible to the HER. Graphical abstract Nitrogen-doped carbon supported fewer-layer MoSe 2 (FL-MoSe 2 /NC) is demonstrated to be an efficient catalyst for the HER. The NC plays an important role in the high performance of the FL-MoSe 2 /NC. It facilitates the formation of MoSe 2 with few layers and shorter lattice fringe lengths and the exposure of more active sites to the HER. Image 1 Highlights • Nitrogen-doped carbon supported few-layer MoSe 2 (FL-MoSe 2 /NC) is prepared. • It exhibits low onset potential and small overpotential. • It exhibits a greatly reduced Tafel slope and a higher exchange current density. • MoSe 2 with few-layers and short fringe lengths exposes more edge and defect sites. • There exists a strong coupling between MoSe 2 and NC. [ABSTRACT FROM AUTHOR]

Phase transition of active electrode materials for pseudocapacitors always plays a pivotal role during the energy storage/release process. Here, large-scale hybrid CoCO 3 /CoO nanostructure arrays were obtained on carbon fiber paper substrate in a mild environment and tested as pseudo-capacitor electrode. After several cycles’ activity, the as-prepared electrodes exhibited good energy storage performance with maximum specific capacitance of 0.77 F/cm 2 in area and 510 F/g in gram at a discharge current of 1 A/g, and 82% of the capacity is retained when the discharge current increased to be 10 A/g from 0.2 A/g, indicating high power capability. Most interestingly, the electrode showed excellent cycling durability with gradually increased capacitance along with cyclic voltammetry at first 5,000 cycles and then maintained at least more than other 15,000 cycles. The initial phase transition of CoCO 3 /CoO to Co(OH) 2 /CoO induced by alkaline electrolyte was demonstrated to be the critical factor for the capacitance enhancement. The phase transition before and after long cycles was discussed through ex-situ X-ray diffraction, Raman and high resolution transmission electron microscope analysis. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene hollow microspheres (NGHSs), synthesized through a template sacrificing method, have been employed as the anode material for lithium ion batteries (LIBs). The electrochemical results show that the NGHSs can exhibit an initial discharge capacity of 2716.4 mAh g −1 , which is significantly higher than the theoretical discharge capacity of graphite (372.0 mAh g −1 ). Further analysis shows that the NGHSs can exhibit significantly high rate capacity, good reversibility, and excellent cycling stability, which clearly demonstrate the potential uses of the NGHSs as the anode material to boost both energy and power densities of LIBs. Their excellent electrochemical performance could be attributed to their specific microspherical hollow structure which consists of nitrogen-doped graphene. The nitrogen doping can greatly increase the reactivity and electrical conductivity of graphene-based carbonaceous materials and create more sites that are active for the Li + ion adsorption, while the hollow microspherical structure allows a ready access of the electrolyte to the electrode surface, easier electron and ion transfer, and faster diffusion of electrolytes in and out of the electrode. In addition, the nitrogen-doped graphene and the specific hollow microspherical structure also make the NGHSs highly stable and can buffer against the local volume change during the Li + detercalation and intercalation processes, which give the corresponding LIBs with better cycling stability. [ABSTRACT FROM AUTHOR]

A 3-dimensional porous graphene material (PGM) has been synthesized using a simple two-step process: hydrothermal reaction and calcination. Hydrothermal reaction of graphene oxide (GO) in the presence of resorcinol and glutaraldehyde leads to covalent grafting of partially reduced GO with glutaraldehyde and the deposition of phenolic resin. Subsequent calcination of the composite consisting of phenolic resin deposited on partially reduced GO in the presence of KOH produces structurally stable, highly porous graphene material with a specific surface area of ∼1,066 ± 2 m 2 g −1 . When used as an active electrode material in a lithium battery, the PGM exhibits an initial discharge capacity of ∼1,538 mAh g −1 , which is significantly higher than those of graphite and other carbonaceous materials reported previously. More importantly, when cycled at higher discharge/charge rates, the PGM-based electrodes still deliver large capacities and excellent cycling performance, demonstrating great potential for high-performance lithium-ion batteries. The attractive electrochemical performance of the PGM is attributed to its unique porous structure with large specific surface area and the presence of more disordered carbon atoms produced by the KOH activation. [ABSTRACT FROM AUTHOR]

In operando Raman spectroscopy has been used to monitor the phase changes of non-stoichiometric α-MnO 2 , α-Mn 0.98 O 2 , electrode materials in a pseudo-capacitor during the charging/discharging process. Results indicate that the α-Mn 0.98 O 2 can be converted to MnO 2 and Mn 3 O 4 when placed in electrolyte exposed to laser for the Raman measurements. Both the phases contribute to the energy storage process through reversible phase transformation which involves hydrated cations M + , protons H + and Mn 2+ intercalation/deintercalation during the charging/discharging process. [ABSTRACT FROM AUTHOR]

• P-doped aminated CNTs supported CoP/NiCoP hetero-nanoparticles (CoP/NiCoP@P-ACNTs) is prepared. • The in-situ phosphorization from the single phase material enables the formation of the CoP/NiCoP heterostructure. • It is demonstrated to be an efficient and stable catalyst for HER over the universal pH range. • The high catalytic activities arise from the strong electronic couplings between CoP, NiCoP, and P-ACNTs. • It can make the ΔGH* value of the CoP/NiCoP@P-ACNTs close to zero and lower the energy barrier for water dissociation. Developing an efficient catalyst for pH-Universal hydrogen evolution is of great interest. This work reports the synthesis of P-doped aminated CNTs supported CoP/NiCoP hetero-nanoparticles (CoP/NiCoP@P-ACNTs) through the in-situ phosphorization of the single phase NiCo 2 O 4 grown on the ACNTs. The in-situ phosphorization from the single phase material enables the formation of the CoP/NiCoP heterostructure, facilitating an electronic coupling between CoP and NiCoP. The CoP/NiCoP@P-ACNTs is demonstrated to be an efficient and stable catalyst for the hydrogen evolution reaction (HER) over the universal pH range. Specifically, it only needs overpotentials of 26.0, 94.0, and 76.8 mV to drive the current density of 10 mA cm−2 in the acidic, neutral, and alkaline solutions, respectively. All of these values are close to those of Pt/C and lower than those of many other catalysts reported recently. The DFT calculations indicate that the high catalytic activities of the CoP/NiCoP@P-ACNTs for the HER arise from the electronic couplings between CoP, NiCoP, and P-ACNTs. They can make the ΔG H* value of the CoP/NiCoP@P-ACNTs close to zero and lower the energy barrier for water dissociation. The CoP/NiCoP@P-ACNTs derived from the in-situ phosphorization of the single phase NiCo 2 O 4 is demonstrated to be an efficient pH-universal catalyst for the HER, which arises from the strong electronic couplings between CoP, NiCoP, and P-ACNTs. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Polymer electrolyte membrane, as the indispensable component of a polymer electrolyte membrane fuel cell, serves a bi-function of conducting protons or hydroxide ions and separating fuels and oxidant, largely determining the performance of the corresponding polymer electrolyte membrane fuel cell. Therefore, the development of polymer electrolyte membranes that can efficiently conduct protons (for proton exchange membrane fuel cells) or hydroxide ions (for anion exchange membrane fuel cells) but block fuel permeation through membranes is a promising way to improve the electrochemical performance of polymer electrolyte membrane fuel cells. The plasma technique has shown great advantages in this area. It has been reported that the polymer electrolyte membranes modified or directly synthesized by the plasma technique exhibit superior properties, such as higher ion conductivity, low fuel permeability, high thermal and chemical stability, which provide them with great potentials as promising polymer electrolyte membranes for polymer electrolyte membrane fuel cell applications. However, the plasma polymerization is a very complicated process which involves the degradation of monomers and the formation of polymers. Therefore, the conditions used for the membrane modification and preparation must be well controlled to obtain membranes with desirable properties. This review paper is concerned with applications of the plasma technique in the preparation of polymer electrolyte membranes for uses in polymer electrolyte membrane fuel cells. The various plasma techniques that have been used for the modification and the preparation of polymer electrolyte membranes are reviewed and their associated advantages and disadvantages are discussed. [Copyright &y& Elsevier]

Abstract: Nanosized LiFePO4/C core/shell nanocomposites with different carbon shell thicknesses have been synthesized by a simple two-step procedure. The effects of carbon shell thickness on the electrochemical performance of these LiFePO4/C core/shell nanocomposites have been investigated. It shows that the LiFePO4/C core/shell nanocomposites with low carbon shell thicknesses exhibit poor electrochemical performance when used in lithium ion batteries, presumably due to presence of structural disorders and defects in the particle surface layers. An increase of carbon shell thickness can remove the structural disorders and defects. The LiFePO4/C core/shell nanocomposites with higher carbon shell thicknesses therefore exhibit significantly improved electrochemical performance. However, further increase of carbon shell thickness would lead to a decrease in the charge/discharge capacity of the LiFePO4/C core/shell nanocomposites, although these LiFePO4/C core/shell nanocomposites still exhibit high cycling stability. That is because excess carbon shell coating would hinder the penetration of the electrolyte solution into the carbon layers and the inward/outward diffusion of Li+ ions through the carbon layers, which decreases the charge/discharge capacity of the LiFePO4/C core/shell nanocomposites. [Copyright &y& Elsevier]

Abstract: A H2 plasma has been used to treat the PtRu nanoparticles supported on the plasma functionalized multi-walled carbon nanotubes (PtRu/PS-MWCNTs). The plasma treatment does not change the size and crystalline structure of PtRu nanoparticles, but reduces the fraction of the oxidized species at the outermost perimeter of particles. The electrochemical results show that these plasma treated PtRu/PS-MWCNTs exhibit increased electrochemically active surface area, improved electrocatalytic activity and long term stability toward methanol and formic acid oxidation, and enhanced tolerance to carbonaceous species relative to the sample untreated with the H2 plasma. The electrocatalytic activities of the plasma treated PtRu/PS-MWCNTs are found to be dependent upon the Pt:Ru atomic ratios of PtRu nanoparticles. The catalysts with a Pt:Ru atomic ratio close to 1:1 show superior properties in the electrooxidation of methanol and formic acid at room temperature and better tolerance to carbonaceous species. [Copyright &y& Elsevier]

Abstract: ZnO nanorods and ZnO nanorods doped with Ce3+ have been synthesized by a solvothermal method. The properties of as-synthesized nanorods were investigated by TEM, X-ray diffraction and photoluminescence spectroscopy. The results showed that Ce3+ doping and increasing concentration could induce the enhancement of photoluminescence. [Copyright &y& Elsevier]

The development of highly-efficient and noble-metal-free catalysts with low cost and high durability for hydrogen evolution reaction (HER) is of great importance to many energy-related technologies. This work reports that nitrogen-doped carbon coated Co nanoparticles encapsulated in bamboo-like nitrogen-doped carbon nanotubes (Co@NC/B-NCNTs), synthesized by a simple calcination of Co(NO 3) 2 , melamine and P123, is a promising catalyst for HER in both acidic and alkaline solutions. In acidic solution, the Co@NC/B-NCNTs has the HER onset potential of ∼0 V and only needs an overpotential of 7 mV to drive the current density of 10 mA cm−2. Its HER catalytic activity is very close to that of Pt/C. In alkaline solution, its onset potential and overpotential to drive 10 mA cm−2 are 100 and 182 mV, respectively. Both the values are lower than those of many other catalysts reported. The DFT calculations show electronic coupling between Co nanoparticles and NC layer plays an important role in high catalytic activity of Co@NC/B-NCNTs. The Co nanoparticles can change the charge density distribution of the outer NC layer, affecting its properties for hydrogen adsorption and desorption. Additionally, the pyridinic N in the outer NC layer is calculated to be a promising active site for HER. The Co@NC/B-NCNTs has demonstrated to be an active catalyst for the HER in both the acidic and alkaline solutions, with the activity comparable to that of the Pt/C in the acidic solution. Image 1 • Nitrogen doped carbon coated Co nanoparticles encapsulated in bamboo-like nitrogen doped carbon nanotubes is synthesized. • Co@NC/B-NCNTs) is highly active for the HER in both the acidic and alkaline solutions. • Its HER catalytic activity is very close to that of the Pt/C, a benchmark catalyst for the HER. • The Co nanoparticles can change the charge density distribution of the outer NC layer, reducing the.|ΔG H∗ | value for hydrogen adsorption and desorption. • The calculation shows that the pyridinic N in the outer NC layer can be a promising active site for the HER. [ABSTRACT FROM AUTHOR]

In this work, plasma under different atmospheres is used to adjust the surface electronic and chemical structure of Fe/Co/N co-decorated hollow graphene spheres (FCNHGS) in order to create suitable conditions for the deposition of Pt 1 Ni 2 alloy nanoparticles (NPs). The results show that plasma treatment in specific atmospheres has different effects on the surface of FCNHGS, such as O 2 plasma is etching and oxidation, N 2 plasma and Ar plasma is etching, Ar/H 2 plasma is etching and reduction, Ar/NH 3 plasma is etching, doping and reduction. Therefore, changing the plasma treatment atmosphere can control the anchoring sites on FCNHGS for the deposition of Pt 1 Ni 2 NPs. When Ar/NH 3 plasma is used, the synthesized Pt 1 Ni 2 @Ar/NH 3 -FCNHGS exhibits the best bi-functional catalytic activity and the highest utilization efficiency of Pt in the oxygen reduction and hydrogen evolution reaction (ORR/HER) due to the strong interaction between loaded Pt 1 Ni 2 NPs and the Ar/NH 3 -FCNHGS. Moreover, when the Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is used as cathode catalyst for direct methanol fuel cell, it exhibits superior open-circuit voltage (OCV = 730 mV) and similar peak power density (PPD = 62.8 mW cm−2) to 20 wt% Pt/C from 25 to 80 °C. More importantly, it showed better stability compared with 20 wt% Pt/C after about 72 h of stability testing. [Display omitted] • The well-dispersed Pt 1 Ni 2 NPs on FCNHGS was achieved by plasma with different atmospheres. • The plasma with different atmospheres produced different defect levels on FCNHGS. • The NPs size is related to the strength of the interaction between the substrate and the alloy NPs. • The OES deduce the formation of defects/functional groups on substrate materials. • The Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is demonstrated to be a stable and efficient catalyst for ORR/HER. [ABSTRACT FROM AUTHOR]

With the emerging climate and environmental problems, it is necessary to develop renewable energy technologies to alleviate the energy crisis. As one of the most promising technologies for hydrogen production, electrocatalytic water splitting has received extensive research attention in recent years, with efficient electrocatalysts as the key to realizing large-scale hydrogen production. After decades of development, non-noble metal-based materials have been widely studied in the fabrication of water splitting catalysts, while these materials still need to be improved compared to commercial noble metal catalysts. Among the many existing electrocatalyst modification strategies, low temperature plasma technology stands out due to the low energy consumption, high efficiency, and low chemical waste generation. Recent advances in the development and application of low temperature plasma technology in the synthesis and modification of electrocatalytic materials for water electrolysis is highlighted. It is expected to provide reference for the design and research of electrode materials in electrocatalytic water splitting with plasma-assisted technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

Noble metal Pt is the acknowledged efficient catalyst for oxygen reduction (ORR) and hydrogen evolution reaction (HER) in commercial applications. However, due to its high price and limited reserves, its large-scale application is limited. In order to overcome this defect, the loaded Pt nanoparticles (NPs) should be small and dispersed efficiently through the design of electrode materials, so as to improve the utilization efficiency of Pt. In addition, the introduction of non-noble metal active sites can reduce the consumption of Pt efficiently. In this work, hollow graphene spheres are used as the carrier and the heteroatoms (N, Fe and Co) are introduced. The results show that the introduction of Fe and Co can form very effective heteroatom active sites (carbon encapsulated Fe/Co metals and FeCo alloy, and/or metal nitrides Fe/Co-N x -C) in the substrate material, which improve the catalytic activity of the electrode material effectively and the utilization efficiency of Pt. In addition, the generation of Fe/Co-N x -C active sites and the loading of Pt are also closely related to the doped N atoms. The onset potential, limiting current density (J L), half-wave potential (E 1/2) and Tafel slope of sample FeCo-N x HGSs/Pt (10 wt%) can exceed or comparable to those of commercial catalysts Pt/C (20 wt%) towards ORR both in acid and alkaline electrolyte. Moreover, the values of η 100 and the Tafel slope for FeCo-N x HGSs/Pt towards HER can also exceed the commercial catalysts Pt/C (20 wt%) in acid and alkaline electrolytes. The purpose of reducing the usage amount of precious metals without reducing the catalytic performance is realized. The relationship between the ORR and HER performance of the resultant electrode catalyst and the doped heteroatoms, such as nitrogen (N), iron (Fe) and cobalt (Co) atoms, was studied and discussed in detail. [Display omitted] • Pyridine and pyrrole N are easy to the formation of metal nitrides (Fe(Co)-N x -C). • Pyridine N is closely related to the rivet of precious metal Pt. • The Fe/Co in HGSs exist in the form of Fe/Co metals, FeCo alloy, Fe/Co-N x -C. • The Fe/Co atoms play a positive role in improving the ORR and HER performance. • The FeCo-N x HGSs/Pt is a stable and efficient catalyst for ORR/HER. [ABSTRACT FROM AUTHOR]

Herein, ultra-low amount Pt is uniformly deposited on the surface of CoFe nanoparticles (NPs) embedded nitrogen-doped carbon nanotubes which are grown directionally on the surface of carbon fiber cloth (Pt–CoFe@NCNT/CFC) using the direct current plasma magnetron sputtering (DC-PMS) technique. The designed electrode exhibits excellent trifunctional catalytic activities towards oxygen reduction reaction (ORR) (in 0.1 M KOH, E 1/2 = 0.807 V; in 0.5 M H 2 SO 4 , E 1/2 = 0.723 V), hydrogen evolution reaction (HER) (in 1 M KOH, η 10 = 17 mV and η 100 = 93 mV; in 0.5 M H 2 SO 4 , η 10 = 42 mV and η 100 = 100.5 mV) and methanol oxidation reaction (MOR) (in 0.5 M H 2 SO 4 + 0.5 M CH 3 OH, peak current density reaches 115 mA mg−1 Pt @1.116 V). It is verified that the DC-PMS technique can greatly improve the utilization efficiency of Pt, so as to reduce the dosage of Pt, and shows better catalytic performance and excellent stability than the commercial Pt/C catalysts. The rich hierarchical heterostructures of the designed electrode can provide more non-noble metal active sites, so as to enhance the catalytic activity and further cut down the consumption of noble metals. Impressively, Pt–CoFe@NCNT/CFC electrode assembled direct methanol fuel cell achieved a remarkable maximum power density of 73.41 mW cm−2 and shows excellent stability. Pt nanoclusters are deposited on the surface of CoFe metal embedded nitrogen-doped carbon nanotubes by DC plasma magnetron sputtering technology, and the designed electrode exhibits excellent trifunctional catalytic activities towards ORR/MOR/HER. [Display omitted] • Pt is uniformly deposited on the surface of CoFe@NCNT/CFC using DC-PMS technique. • Abundant non-noble metal active sites are beneficial to reduce the consumption of Pt. • It provides abundant rivet points for the efficient deposition of Pt. • It shows stable and efficient ORR/MOR/HER multi-functional catalytic performance. • The assembled DMFC exhibits good performance and excellent stability. [ABSTRACT FROM AUTHOR]

Here, a simple, economical one-step doping strategy is adopted to prepare N, S co-doped graphene hollow spheres (NSGHS). The NSGHS exhibits remarkable oxygen-reduction-reaction (ORR) activity with a high half-wave potential (E 1/2) of 0.847 V vs. RHE and considerable long-term stability. When applied as anode materials for sodium-ion batteries (SIBs), it could deliver a high reversible capacity of 385 mAh g−1 at 500 mA g−1, excellent rate performance of 308 mAh g−1 at even 20 A g−1 and superior cycling performance at 10 A g−1 during 5000 cycles with negligible capacity fade. DFT calculation reveals that the doping of N and S endows the surrounding carbon with high positive charge and spin density, respectively, making them be highly active ORR catalytic sites except for S itself. Despite the possible oxidization of C–S–C active sites, the rest C atoms of NSGHS will still hold a considerably high catalytic activity superior to those of mono-doped or undoped cases. In addition, S doping will improve the binding between Na and graphene substrate to get a high capacity and N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites, thus the excellent stability for ORR and SIBs. [Display omitted] • A simple, economical one-step doping strategy is adopted to prepare NSGHS. • The NSGHS exhibits excellent ORR activity and Na storage performance. • The doping of N and S endows the surrounding carbon with high positive charge and spin density. • S doping will improve the binding between Na and graphene substrate to get a high capacity. • N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the core reaction processes of rechargeable Zn-air battery (ZAB) cathode. Therefore, exploring a bifunctional catalyst with excellent electrochemical performance, high durability, and low cost is essential for rechargeable ZAB. In this work, amino functionalized carbon nanotubes supported core/shell nanoparticles composed of CoNi alloy core and CoO–NiO shell (CoNi@CoO–NiO/NH 2 -CNTs-1) is synthesized through a simple and efficient hydrothermal reaction and calcination method, which shows higher ORR/OER bifunctional catalytic performance than the single metal-based catalyst, such as Ni@NiO/NH 2 -CNTs and Co@CoO/NH 2 -CNTs. The fabricated bimetallic alloy based catalyst CoNi@CoO–NiO/NH 2 -CNTs-3 with the optimized loading content of CoNi@CoO–NiO core/shell nanoparticles, presents the best bifunctional catalytic performance for ORR/OER. Experimental studies reveal that CoNi@CoO–NiO/NH 2 -CNTs-3 exhibits the onset potential of 0.956 V and 1.423 V vs. RHE for ORR and OER, respectively. It also exhibits a low overpotential of 377 mV to achieve a 10 mA cm−2 current density for OER, and positive half-wave potentials of 0.794 V for ORR. And the potential difference between half-wave potential of ORR (E 1/2) and the potential at 10 mA cm−2 for OER (E j10) is 0.813 V. In addition, when CoNi@CoO–NiO/NH 2 -CNTs-3 is used as an air electrode catalyst of rechargeable ZAB, its maximum power density and open circuit voltage (OCV) can reach 128.7 mW cm−2 and 1.458 V (The commercially available catalyst of Pt/C–RuO 2 is 88.1 mW cm−2), which strongly demonstrates that the fabricated catalyst CoNi@CoO–NiO/NH 2 -CNTs-3 can be used as a highly efficient bifunctional catalyst for ZABs, and is expected to replace those expensive precious metal electrocatalysts to meet the growing demand for new energy devices. Amino functionalized carbon nanotubes supported core-shell nanoparticles composed of CoNi alloy core and CoO–NiO shell (CoNi@CoO–NiO/NH 2 -CNTs) is successfully prepared by a simple, green and sustainable method for application in rechargeable Zn-air batteries. Image 1 • NH 2 -CNTs supported core/shell CoNi@CoO–NiO nanoparticles is synthesized. • It shows higher ORR/OER catalytic performance than the single metal-based catalyst. • The CoNi@CoO–NiO/NH 2 -CNTs-3 presents optimal bifunctional catalytic performance. • The maximum power density of the assembled ZAB can reach 128.7 mW cm−2. [ABSTRACT FROM AUTHOR]

Herein, the relationship between oxygen reduction reaction (ORR) catalytic activities of N-doped hollow graphene spheres (N-HGSs) and their morphologies, microstructures, and nitrogen doping configuration is deeply investigated. Based on all detection results it can be concluded that all of the level and configuration of doped-N atoms, the surface area, the mesopore structure of fabricated hollow graphene spheres related to the exposure of edges and vacancies correlating with the active sites, will ultimately affect the ORR catalytic performance of N-HGSs. Therefore, the optimized synthesis of N-HGSs can produce efficient electrocatalyst for ORR, which is better than the noble-metal Pt/C catalysts and most highly active graphene-based ORR catalysts reported to date. Additionally, the optimized synthesis of N-HGSs also exhibit excellent performance in sodium-ion storage. Because the large specific surface area, the well-connected hollow spherical and mesopore structures and the increased hydrophilicity induced by the doped-N atoms facilitate a ready transfer of charges and adsorption, diffusion and desorption of Na+ ions in and out of the active material, which could enhance sodium ion storage capacity. Additionally, expect the storage of Na+ ions by surface electro-adsorption/desorption, the insertion/extraction of Na+ through the thinner graphene shell makes a significant contribution to the improvement of sodium-ion storage capacity. Image 1 • N-doping configuration, surface area, microstructure affect ORR performance. • The mesopore structure is correlating with the ORR active sites. • The optimized N-HGSs exhibit excellent performance in ORR and sodium ion storage. • Hollow spherical and mesopore structures enhance sodium ion storage capacity. • Insertion/extraction of Na+ through thinner graphene shell enhances performance. [ABSTRACT FROM AUTHOR]

A metal-free highly torn amine functionalized nitrogen doped graphene (HT-AFNG) used as hydrogen evolution reaction (HER) catalyst is prepared by using a simple synthesis method involving the hydrothermal reaction of graphene oxide in the presence of ammonia and the subsequent ball milling. The metal-free HT-AFNG is efficient for the HER in the acid solution and can deliver an onset potential of 100 mV and an overpotential of 350 mV at the current density of 10 mA cm −2 , which is much lower than those of the singly and dually doped graphene reported previously. The amine functionalized and nitrogen doped structure plays an important role in the high catalytic activity of the HT-AFNG, where the amine group can greatly reduce the |ΔG H* | value at both defect and edge sites as well as increases the electron transfer capability of nitrogen dope graphene (NG). Significantly, the highly torn structure also makes a big contribution on the high catalytic activity of the HT-AFNG, since it allows for the good accessibility of the active sites for the HER. The strategy involves the introduction of electron donating groups open a new research pathway towards the improvement of HER catalytic activity of graphene-based materials. [ABSTRACT FROM AUTHOR]

The MnO@nitrogen doped carbon microspheres with a yolk-shell structure (YS-MnO@NC) is reported. As an anode for lithium ion battery, the YS-MnO@NC exhibits a very high reversible capacity (1280 mA h g −1 at 0.1 A g −1 ), superior rate capability (capacities of 1090, 860, 700, 545, and 390 mA h g −1 at 0.2, 0.5, 1.0, 2.0, and 5.0 A g −1 , respectively), and stable cycling performance (880 mA h g −1 at 1.0 A g −1 after 1000 cycles). The reversible capacity and cyclability of YS-MnO@NC is higher than MnO based materials reported previously. Its remarkable performance is attributable to the unique yolk-shell structure and the presence of the NC shell. Specifically, the yolk-shell structure improves its structural stability during the repeated cycles due to the presence of the internal void between the core and shell, while the NC shell increases its electric conductivity and wettability toward the electrolyte solution. Additionally, the nitrogen doped structure also promotes a strong electronic coupling between MnO and NC. The in operando X-ray diffraction studies show that the MnO core and hollow NC microsphere play comparatively equal contributions on the high performance of the YS-MnO@NC. Both the NC shell and MnO microsphere exhibit high reversibility in lithiation and delithiation. [ABSTRACT FROM AUTHOR]

Nitrogen-rich graphene hollow microspheres (NGHMs) have been synthesized by simply calcining the core@shell polystyrene@graphene oxide (PS@GO) microspheres in the presence of melamine. These NGHMs are highly active as the anode for sodium ion batteries (SIBs) and can deliver a stable reversible capacity of 253.8 mAh g −1 at 100 mA g −1 , which is much higher than that of the conventional nitrogen doped graphene (102.3 mAh g −1 ). Additionally, the NGHMs exhibit excellent rate and cycling performance. A high stable discharge capacity of 77.8 mAh g −1 could be observed when the NGHMs are cycled for 8000 cycles at 10 A g −1 . At 20 A g −1 , the NGHMs can still deliver a reversible capacity of 66.7 mAh g −1 . The capacities of the NGHMs are higher than those of most carbonaceous materials reported. These results strongly suggest that the NGHMs are usable as the anode for the SIBs with high-rate performance and super-long life time. The specific hollow structure is found to play an important role in the high performance of the NGHMs. It does not only increase specific surface area of the NGHMs, allowing for more active sites available to the Na + storage, but also allows a ready diffusion of the Na + ions. [ABSTRACT FROM AUTHOR]

High specific capacitance, large surface area, good flexibility and super durability are recognized as advantageous characteristics to acquire ideal supercapacitor, but it is a great challenge to realize them at the same time. Here, a novel cobalt-nickel layered double hydroxide nanoflakes grow on carbon nitride coated N-doped graphene hollow spheres is successfully assembled by a facile chemical bath deposition method. The carbon nitride coated N-doped graphene hollow spheres scaffold not only possesses large surface area for increasing loading of electroactive material but also has hollow structure for accelerating electron and ion transport. Owing to synergistic contributions, the resulting Co 1 Ni 1 layered double hydroxide nanoflakes on carbon nitride coated N-doped graphene hollow spheres with large surface area of 268 m 2 g −1 exhibited enhanced specific capacitance (1815 F g −1 at 1 A g −1 ) and excellent cycling stability (82.1% retention after 4,000 cycles even at 20 A g −1 ). In addition, the capacitance retention still keeps 90.7% after rolling-up about 360° due to wonderful flexibility. Finally, an asymmetric supercapacitor is assembled to further investigate its practical application, which exhibited high energy density of 28.9 Wh kg −1 at an average power density of 1875 W kg −1 and outstanding capacitance retention (no any losses of initial specific capacitance after 10,000 cycles). These advantageous characteristics demonstrate that the new electrode gives a comprehensive application prospect in miniaturized and flexible energy storage. [ABSTRACT FROM AUTHOR]

The sandwiched membrane which consists of the sulfonated holey graphene oxide paper with the deposition of the sulfonated poly(ether ether ketone) (SPEEK/SHGO/SPEEK) membrane on its both sides has been prepared. This membrane is reported to have higher proton conductivity (155.6 ± 1.6 mS cm −1 ), but lower methanol permeability (7.05 ± 0.21 × 10 −6 cm 2 s −1 ) than Nafion ® 112 at 80 °C, whose respective values are 138.6 ± 1.4 mS cm −1 and 15.40 ± 0.46 × 10 −6 cm 2 s −1 , respectively. The specific structure of the SHGO comprising the sulfonated and holey graphitic plane plays an important role in the high performance of the SPEEK/SHGO/SPEEK membrane. First, the sulfonated structure could increase the overall density of the sulfonic acid groups in the membranes, which increases the number of proton exchange groups participating in the proton transport. Second, the holey structure of the SHGO provides an additional path for the proton transport, which well avoids the blockage of the proton transport by the high aspect ratio graphitic planes. Third, the sulfonated and holey structure could also increase the interlayer spacing of the graphitic planes in the SHGO paper, which would promote the proton transport as well. Finally, the presence of the SHGO paper with the layer-by-layer stacked graphitic plane would effectively retard the diffusion of methanol through the membrane. When evaluated in the semi-passive direct methanol fuel cell (DMFC), the cell with the SPEEK/SHGO/SPEEK membrane shows higher stability and exhibits a maximum power density 61.1% higher than with Nafion ® 112, which strongly suggests that the SPEEK/SHGO/SPEEK membrane could be used as the proton exchange membrane for DMFCs. [ABSTRACT FROM AUTHOR]

Sulfonated poly(ether ether ketone) (SPEEK) membranes have been deposited on the both sides of a sulfonic acid functionalized graphene oxide (SGO) paper to form a proton exchange membrane (PEM) with a sandwiched structure. The obtained SPEEK/SGO/SPEEK membrane could exhibit proton conductivity close to Nafion ® 112 and lower methanol permeability. The use of this SPEEK/SGO/SPEEK membrane greatly improves the performance of the semi-passive direct methanol fuel cell (DMFC). The semi-passive DMFC with the SPEEK/SGO/SPEEK membrane is found to be capable of delivering the peak power density 60% higher than that with the commercial Nafion ® 112. This, along with its comparable durability to Nafion ® 112, strongly suggests the great promise of using the SPEEK/SGO/SPEEK membrane as the PEM. [ABSTRACT FROM AUTHOR]

It is of great significance to improve the performance of electrocatalysts by constructing suitable heterogeneous interfaces to adjust the electronic structure of their surfaces. Here, we design and synthesize Co-Fe alloy nanoparticles (NPs) modified nitrogen-doped cubic carbon box (NC) supported MoS 2 nanosheets (NC@MoS 2 @Co-Fe) as a bi-functional electrocatalytic electrode material, which possesses excellent electrocatalytic oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance. The NC@MoS 2 @Co-Fe exhibits remarkable bifunctional electrocatalytic activities with an ORR half-wave potential of 0.73 V in 0.1 M KOH electrolyte and an OER overpotential of 400 mV, driving a current density of 10 mA cm−2. The advanced catalytic performance can be attributed to the unique heterojunction structure of the catalyst. The size of the Co-Fe alloy NPs supported on MoS 2 can be tuned to avoid the excessive growth of alloy NPs and to expose more catalytic active sites. Meanwhile, the loaded Co-Fe alloy NPs should be covered with a calcined carbon layer derived from the organic ligand to prevent oxidation passivation and particle aggregation. The structure formed by Co-Fe alloy NPs and NC@MoS 2 optimizes the electronic structure of the active center and accelerates the electrocatalytic reaction rate, thus synergistically improving the bi-functional electrocatalytic activity of the NC@MoS 2 @Co-Fe catalyst and can be applied to rechargeable zinc air batteries. Co-Fe alloy nanoparticles (NPs) modified nitrogen-doped cubic carbon box (NC) supported MoS 2 nanosheets (NC@MoS 2 @Co-Fe) is synthesized as a bi-functional electrocatalytic electrode material, which possesses excellent electrocatalytic oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance. [Display omitted] • The NC@MoS 2 @Co-Fe exhibits remarkable bi-functional electrocatalytic activities. • The assembled Zn-air batterie delivers a high power density and superior cycling performance. • The precise control of Co-Fe alloy on the surface electronic structure is realized. • The hollow nitrogen doped carbon box has a good electrolyte diffusion channel. • The unique MoS 2 @Co-Fe heterojunction structure optimizes the electronic structure of the active center. [ABSTRACT FROM AUTHOR]

• Plasma-assisted phosphorization could construct Ni 12 P 5 /ZnP 2 heterojunction. • The P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 is an excellent bifunctional catalyst. • It needs an overpotential of 82 mV vs. RHE to offer 10 mA cm−2 for HER. • It needs an overpotential of 360 mV vs. RHE to offer 100 mA cm−2 for OER. • The P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 (+, −) alkaline elctrolyzer showed superior performance. Plasma assisted phosphorization is employed to obtain homogeneous nickel phosphide and zinc phosphide nanoparticles (NPs) distributed over the surface of MoS 2 nanosheets. It exhibits admirable bifunctional catalysis activity towards water electrolysis. [Display omitted] Herein, Zn single atom supported MoS 2 nanosheets growing on nickel foam (NF) is formed by in-situ growth of MoS 2 nanosheets and ZIF-8 and high temperature carbonization. And then plasma-assisted-phosphorization is employed to obtain homogeneous nickel phosphide (Ni 12 P 5) and zinc phosphide (ZnP 2) heterojunction nanoparticles (NPs) distributed over the surface of MoS 2 nanosheets (P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2). The MoS 2 nanosheets growing on 3D NF framework benefits the increase of the electrochemically active specific surface, and the uniform distribution of heterojunction Ni 12 P 5 /ZnP 2 NPs exposes more catalytic active sites. Moreover, the heterojunction Ni 12 P 5 /ZnP 2 NPs obtained by plasma-assisted-phosphorization has smaller size and stronger electronic coupling than that synthesized by the conventional thermal phosphorization (C-Ni/MoS 2 @Ni 12 P 5 /ZnP 2). Therefore, the as-synthesized P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 shows an excellent bifunctionality catalytic activity for both HER and OER in alkaline solutions, which is highlighted by the overpotential at 82 mV for delivering current density of 10 mA cm−2 for HER and 360 mV for delivering 100 mA cm−2 for OER. P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 exhibits higher electrocatalytic performance and better stability than most previously reported bifunctional catalysts. Furthermore, the catalytic current density of P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 as a bifunctional catalyst assembled single two-electrode-electrolyzer rapidly exceeded 50 mA cm−2 at a low cell voltage of 1.62 V, surpassing the commercial RuO 2 -Pt/C coupled electrolyzer. [ABSTRACT FROM AUTHOR]

• The spherical hollow graphene doped with different nitrogen structures are prepared. • The structures of doped N effect on the growth, shape, crystal structure of MoS 2+x. • PS is helpful for the uniform growth of MoS 2+x and the exposure of active sites. • The MoS 2+x composed of crystalline and amorphous states. • MoS 2+x supported on NH 2 -NHGSs exhibits the best HER activity. [Display omitted] MoS 2 , a two-dimensional (2D) layered structural transition metal dichalcogenide (TMDs), has been widely investigated towards hydrogen evolution reaction (HER) in previous few years. Except for the inert basal plane sites of the MoS 2 itself, its inherent low conductivity also hinders the electron transfer process, which adversely affects its efficiency towards HER. Therefore, how to expose more edge active sites and at the same time improve the conductivity of MoS 2 , either intrinsically or with the help of high conductive substrates, is a key means to improve the HER performance of MoS 2. Herein, the polystyrene (PS) nanospheres are used not only as an intercalation agent of graphene carbon sheets, but also as a spherical template for the preparation of 3D spherical hollow graphene. Different nitrogen precursors and nitrogen doping methods are used to prepare the 3D spherical hollow graphene substrate materials with different nitrogen-doping structures, such as amine N, pyrrolic N, pyridinic N or quaternary N. The investigation results show that the structure of doped nitrogen atom has a great influence on the loading of molybdenum disulfide. Among them, amine N was the most favorable for the loading of molybdenum disulfide, followed by pyrrole N, quaternary N and pyridine N. Moreover, the structure of doped N active sites synthesized by different preparation methods can also affect the uniform distribution of molybdenum disulfide on 3D spherical hollow graphene and the corresponding HER performance. The results show that, using ammonia as nitrogen source and PS microspheres as template, the prepared molybdenum disulfide loaded 3D spherical hollow graphene electrode material has the best HER performance, which should be attributed to the uniform distribution of the molybdenum disulfide and its close combination with the substrate, as well as the 3D spherical hollow structure. Moreover, the amorphous structure of molybdenum disulfide formed in the hydrothermal process can also improve the activity of HER. [ABSTRACT FROM AUTHOR]