time further and enhance power density during acceleration process so as to perfect its practicality. [1b,3] Electrode materials (cathode and anode) play an important role in the electrochemical properties of LIBs, including energy-density, cycle-life, rate capability, and safety among others. Graphite materials with high capacity greater than 300 mAh g −1 , superior structural stability, as well as low cost are significantly applied as anode electrode in commercialized LIBs. [4] The other anode, graphite/silicon composites that can deliver higher capacity of around 1000 mAh g −1 and that of pure graphite electrode are gradually commercialized to further enhance the energy density of LIBs. [5] The first commercial cathode material, layered oxide LiCoO 2 with O3 structure (in which oxygen anion have a cubic close packing arrangement in the form of ABCABC…), illustrates the unpleasant transformation from hexagonal phase to monoclinic phase, particularly when the Li + deintercalation ratio (x) exceeds 0.5 in Li 1−x CoO 2 . [6] This is in contrast with graphite-based anode with preferred electrochemical performance and low cost. Also, this phase transition derived from the order/disorder transformation of Li + is anticipated to cause rapid decay of reversible capacity. [6d] Consequently, the LiCoO 2 cathode can only deliver around 150 mAh g −1 , which has limi ted the performance promotion of LIBs and the far-ranging applications of LIBs in PHEVs and EVs.Additionally, developing high-capacity (energy-density) cathode materials with desired electrochemical behaviors in place of the conventional LiCoO 2 has been the main motivation behind LIBs in the recent past. Three main groups of cathode materials, layered oxides including lithium-stoichiometric Li[Ni x Co y Mn 1−x−y ]O 2 and lithium-rich Li 1+z M 1−z O 2 (M = Mn, Ni, Co, Ru, Sn, Ir, etc.), spinel LiM 2 O 4 (M = Ni, Mn), together with olive LiMXO 4 (M = Fe, Mn, Co; X = P, Si) as illustrated in Figure 1, are broadly examined as the next-generation cathode materials for LIBs. [3a,6e,7] Among these candidates lithiumrich and manganese-based layered oxides display the highest energy-density of approach 1000 Wh Kg −1 as a result of the large reversible capacity of ≈300 mAh g −1 and high voltage of 3.5 V (vs. Li/Li + ). However, there are various significantThe urgent prerequisites of high energy-density and superior electrochemical properties have been the main inspiration for the advancement of cathode materials in lithium-ion batteries (LIBs) in the last two decades. Nickel-rich layered transition-metal oxides with large reversible capacity as well as high operating voltage are considered as the most promising candidate for next-generation LIBs. Nonetheless, the poor long-term cycle-life and inferior thermal stability have limited their broadly practical applications. In the research of LIBs, it is observed that surface/interfacial structure and chemistry play significant roles in the performance of cathode cycling. This is due to the fact that they are basical...

Robust and highly active photocatalysts, CdS@MoS, for hydrogen evolution were successfully fabricated by one-step growth of oxygen-incorporated defect-rich MoS ultrathin nanosheets on the surfaces of CdS with irregular fissures. Under optimized experimental conditions, the CdS@MoS displayed a quantum yield of ∼24.2% at 420 nm and the maximum H generation rate of ∼17203.7 umol/g/h using NaS-NaSO as sacrificial agents (λ ≥ 420 nm), which is ∼47.3 and 14.7 times higher than CdS (∼363.8 μmol/g/h) and 3 wt % Pt/CdS (∼1173.2 μmol/g/h), respectively, and far exceeds all previous hydrogen evolution reaction photocatalysts with MoS as co-catalysts using NaS-NaSO as sacrificial agents. Large volumes of hydrogen bubbles were generated within only 2 s as the photocatalysis started, as demonstrated by the photocatalytic video. The high hydrogen evolution activity is attributed to several merits: (1) the intimate heterojunctions formed between the MoS and CdS can effectively enhance the charge transfer ability and retard the recombination of electron-hole pairs; and (2) the defects in the MoS provide additional active S atoms on the exposed edge sites, and the incorporation of O reduces the energy barrier for H evolution and increases the electric conductivity of the MoS. Considering its low cost and high efficiency, this highly efficient hybrid photocatalysts would have great potential in energy-generation and environment-restoration fields.

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively).

In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo2O4 utilized as the supercapacitor electrodes.

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