NiMn2O4 with different crystal structures was successfully synthesized and evaluated as a cathode catalyst for rechargeable Li–air batteries for the first time. The result reveals that the intermediate spinel structure between normal and inverse spinels demonstrates faster kinetics towards ORR/OER than the normal spinel, leading to a better battery performance.

SnO2 and SnO2@C have been successfully synthesized with a simple hydrothermal procedure combined with heat treatment, and their performance as cathode catalysts of Li-air batteries has been comparatively evaluated and discussed. The results show that both SnO2 and SnO2@C are capable of catalyzing oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) at the cathode of Li-air batteries, but the battery with SnO2@C displays better performance due to its unique higher conductivity, larger surface area, complex pore distribution, and huge internal space.

•The catalytic performance of low cost commercial VC is investigated.•The work points a new way to develop transitional metal based non-noble catalyst.•Nitrogen doping to VC increases the ORR potential.Transitional metal carbides have great potential to overcome the shortcomings of high-cost and rare sources of precious metal based catalysts. In this paper, we report the catalytic performances of commercial vanadium carbide (VC) and the influences of nitrogen doping on its catalytic performance towards oxygen reduction reactions. Results showed that nitrogen has been doped into the crystal lattice of commercial VC with a slight increase of crystalline size. The half-wave potential of oxygen reduction of the commercial VC and nitrogen doped VC was only 0.06 V and 0.04 V lower than that of Pt/C catalyst, respectively. The stability of VC for catalyzing oxygen reduction could be improved by nitrogen doping.Download high-res image (122KB)Download full-size image

Rechargeable lithium air (Li–air) batteries, especially the non-aqueous type, are considered the most promising energy storage and conversion device candidates for use in future electric vehicle applications due to their ultrahigh energy density. The air cathode has been identified as a key factor affecting the overall performance of Li–air batteries. The current low level performance of air cathodes is the major challenge hindering commercial applications of Li–air batteries. In the past decade, a great many cathode materials, structures and fabrication processes have been developed and investigated with the goal of enhancing cathode performance. This paper reviews, the role of the cathode in non-aqueous Li–air batteries including the cathode reaction mechanisms and the properties and morphologies of cathode materials, followed by approaches to optimize cathode performance. The most recently published global progress and the main achievements in the field of Li–air batteries are also systematically and critically reviewed in terms of cathode materials, structures and fabrication processes, with the objective of providing some state-of-the-art information. Technical challenges are analyzed, and insights into future research directions for overcoming these development challenges of rechargeable non-aqueous Li–air battery cathodes are also identified in this review paper.

•A novel strategy for uniformly dispersed bi-component nanocomposite.•Porous and hollow-structured Ni0.14Mn0.86O1.43 microspheres as anode for LIBs.•Ni0.14Mn0.86O1.43 exhibit excellent high rate capability and exciting lifespan.A uniformly dispersed bi-component nanocompotise of transition metal oxide (Mn2O3)/mixed transition metal oxide (NiMn2O4) with a porous and hollow microspheric sructure has been successfully prepared with a facile method based on the complexation between Ni2+ and NH3. The obtained nanocomposite of 0.29 Mn2O3/0.14 NiMn2O4, expressed as Ni0.14Mn0.86O1.43, with nanometer-sized building blocks exhibits a high reversible capacity of 615 mA h g−1, which is about 90% of theoretical value at the current density of 800 mA h g−1, and long lifespan with retained capacities of 553 and 408 mA h g−1 after 150 cycles at 200 and 800 mA g−1, respectively, as an anode material for lithium-ion batteries.A novel Mn2O3/NiMn2O4 nanocomposite (Ni0.14Mn0.86O1.43) with a porous and hollow microspheric architecture has been developed as high-rate and long-life anode material of lithium ion batteries.

A double perovskite oxide Sr2CrMoO6−δ (SCM), synthesized using the sol–gel and annealing method with the assistance of citric acid and ethylene diamine tetraacetic acid, was investigated for the first time as an efficient catalyst for rechargeable lithium air batteries. The SCM cathode enables higher specific capacity, lower overpotential and a much better cyclability compared to the pure Super P electrode owing to its excellent electrocatalytic activity towards the formation/decomposition of Li2O2.

•Co–PPy–TsOH/C as electrocatalysts towards oxygen reduction reaction (ORR).•Effects of acid leaching and second heat treatment on catalyst performance.•Effects of cobalt loading on catalyst performance.•The identified ORR active site in the Co–PPy–TsOH/C catalysts.A series of carbon supported cobalt–polypyrrole–4-toluenesulfinic acid have been pyrolyzed in an argon atmosphere at 800 °C, then structurally characterized and electrochemically evaluated as oxygen reduction reaction (ORR) catalysts in aqueous 0.5 M sulfuric acid. The structures are cobalt bonded to nitrogen species (Co–Nx) along with metallic cobalt and cobalt oxide. When the cobalt loading in the compound is less than 1.0 wt%, the predominate form is Co–Nx, when the loading is higher than 1.0 wt%, metallic Co and Co oxide particles co-exist with the Co–Nx compound. At a Co loading of ∼1.0 wt%, the catalyst gives the best ORR activity. Both metallic Co and Co oxide are not active for catalyzing ORR, and block the catalytically active Co–Nx species from the surface and reduce the catalytic activity since the diffusion limiting current density on a rotating disk electrode (RDE) increases when the electrode blocking agents are washed away with acid.

•Pyrolyzed carbon-supported cobalt-polypyrrole as catalyst towards ORR.•Effects of pyrolysis temperature and duration on the ORR performance.•Transformation of cobalt acetate into CoO and then metallic cobalt.•Quaterary-N plays important role on the ORR performance.•Pyrolysis at 800 °C for 2 h is the optimal condition to prepare the best catalyst.A series of non-precious metal catalysts named as Co-PPy-TsOH/C towards oxygen reduction reaction (ORR) were synthesized by pyrolyzing carbon supported cobalt-polypyrrole at various temperatures for diverse durations. The catalytic activity of these catalysts was evaluated with electrochemical techniques of cyclic voltammetry, rotating disk electrode and rotating ring-disk electrode. Physicochemical techniques, such as XRD, TEM and XPS, were employed to characterize the structure/morphology of the catalysts in order to understand the effects of pyrolysis conditions on the ORR activity. The results showed that both pyrolysis temperature and the duration have essential effects on the structure/morphology as well as ORR activity of the Co-PPy-TsOH/C catalysts, pyrolyzing the precursor at 800 °C for 2 h is the optimal condition to synthesize the catalyst with the best ORR performance.

•Co-PPy-TsOH/C as catalysts towards oxygen reduction reaction (ORR).•Co-PPy-TsOH/C prepared with various amount of pyrrole and TsOH.•Elemental contents of Co, N, C, S, H and O in Co-PPy-TsOH/C catalysts.•Electrochemical properties of ORR peak potential and electron-transfer number.•Correlation between pyrrole/TsOH amount, elemental contents and properties.A family of non-precious metal catalysts, Co-PPy-TsOH/C, has been synthesized with different amount of pyrrole and p-toluenesulfonic acid (TsOH). Elemental contents of Co, N, C, S, H and O in the obtained catalysts have been measured with physicochemical techniques and the performance of these catalysts towards oxygen reduction reaction (ORR) have been evaluated with electrochemical techniques. Then, the results obtained have been discussed with principal component analysis and linear correlation analysis to find the correlation/anticorrelation between the composition and electrochemical properties. It is revealed that the used amount of pyrrole has much more apparent effect than TsOH on elemental contents in the Co-PPy-TsOH/C catalysts, while both of them influence the ORR activity and mechanism of the catalysts. Besides, the effects of the contents of each element on the electrochemical performance have also been analyzed to guide the future development of similar catalysts.

In this study, a series of Fe-based non-noble metal and non-macrocycle catalysts, FeTETA/C, for oxygen reduction reaction (ORR) have been synthesized by pyrolyzing carbon-supported iron triethylenetetramine chelate at various temperatures in an inert atmosphere. Electrochemical characterization revealed that heat treatment temperature plays an essential role on improving the catalytic property of the obtained catalysts for ORR, and the optimal could be achieved at 800 °C with an ORR peak potential of 0.751 V and an electron-transfer number of 3.85. Furthermore, the obtained optimal catalyst has excellent methanol-tolerance and acceptable acid-resistance. The effects of heat treatment temperature on microstructure of the catalysts as well as the elemental state on the optimal catalyst surface have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

A promising non-precious metal FeCoTETA/C catalyst has been easily synthesized, by chelating Fe and Co with triethylenetetramine (TETA) in ethanol followed by pyrolyzing in an Ar atmosphere, as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The catalyst has been characterized with various physicochemical techniques as well as electrochemical analysis and single cell performance measurement. The results showed that nano-intermetallic FeCo particles and several types of N and O species are present on carbon matrix. The catalyst delivers better electrocatalytic activity toward ORR compared with CoTETA/C catalyst, the %H2O2 is about 10% with an electron-transfer number of around 3.8. The PEMFC with this catalyst in cathode reaches a maximum power density of 256 mW cm−2 and has a current density of 514 mA cm−2 at 500 mV.

Several 6-aminoquinoline derivatives, which could be used in drug design, have been synthesized. The reaction conditions were comparatively studied, and the p-chloroaniline was used as optimum oxidant in Skraup–Doebner–Von Miller reaction. The nitro group was reduced effectively by SnCl2 with no halo-removed occurred.

Co–Cu–B, as a catalyst toward hydrolysis of sodium borohydride solution, has been prepared through chemical reduction of metal salts, CoCl2·6H2O and CuCl2, by an alkaline solution composed of 7.5wt% NaBH4 and 7.5wt% NaOH. The effects of Co/Cu molar ratio, calcination temperature, NaOH and NaBH4 concentration and reaction temperature on catalytic activity of Co–Cu–B for hydrogen generation from alkaline NaBH4 solution have been studied. X-ray diffraction (XRD), scanning electron microscope (SEM) and Nitrogen adsorption–desorption isotherm have been employed to understand the results. The Co–Cu–B catalyst with a Co/Cu molar ratio of 3:1 and calcinated at 400 °C showed the best catalytic activity at ambient temperature. The activation energy of this catalytic reaction is calculated to be 49.6 kJ mol−1.

A double perovskite oxide Sr2CrMoO6−δ (SCM), synthesized using the sol–gel and annealing method with the assistance of citric acid and ethylene diamine tetraacetic acid, was investigated for the first time as an efficient catalyst for rechargeable lithium air batteries. The SCM cathode enables higher specific capacity, lower overpotential and a much better cyclability compared to the pure Super P electrode owing to its excellent electrocatalytic activity towards the formation/decomposition of Li2O2.

NiMn2O4 with different crystal structures was successfully synthesized and evaluated as a cathode catalyst for rechargeable Li–air batteries for the first time. The result reveals that the intermediate spinel structure between normal and inverse spinels demonstrates faster kinetics towards ORR/OER than the normal spinel, leading to a better battery performance.