The durability and reactivity of catalysts can be effectively and precisely controlled through the careful design and engineering of their surface structures and morphologies. Herein, we develop a novel "adsorption-calcination-reduction" strategy to synthesize spinel transitional metal oxides with a unique necklace-like multishelled hollow structure exploiting sacrificial templates of carbonaceous microspheres, including NiCoO (NCO), CoMnO, and NiMnO. Importantly, benefiting from the unique structures and reduction treatment to offer rich oxygen vacancies, the unique reduced NCO (R-NCO) as a bifunctional electrocatalyst exhibits the dual characteristics of good stability as well as high electrocatalytic activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). At 1.61 V cell voltage, a 10 mA cm water splitting current density is obtained from the dual-electrode, alkaline water electrolyzer. Calculations based on density functional theory (DFT) reveal a mechanism for the promotion of the catalytic reactions based on a decrease in the energy barrier for the formation of intermediates resulting from the introduction of oxygen vacancies through the reduction process. This method could prove to be an effective general strategy for the preparation of complex, hollow structures and functionalities.

We demonstrated in this paper the shape-controlled synthesis of ZnIn2S4, CuInS2, and CuInSe2 nano- and microstructures through a facile solution-based route. One-dimensional ZnIn2S4 nanotubes and nanoribbons were synthesized by a solvothermal method with pyridine as the solvent, while ZnIn2S4 solid or hollow microspheres were hydrothermally prepared in the presence of a surfactant such as cetyltrimethylammonium bromide (CTAB) or poly(ethylene glycol) (PEG). The mechanisms related to the phase formation and morphology control of ZnIn2S4 are proposed and discussed. The UV-vis absorption spectra show that the as-prepared nano- and micromaterials have strong absorption in a wide range from UV to visible light and that their band gaps are somewhat relevant to the size and morphology. The photoluminescence measurements of the ZnIn2S4 microspheres at room temperature reveal intense excitation at approximately 575 nm and red emission at approximately 784 nm. Furthermore, CuInS2 and CuInSe2 with different morphologies such as spheres, platelets, rods, and fishbone-like shapes were also obtained by similar hydrothermal and solvothermal synthesis.

Rechargeable aluminum-ion batteries (AIBs) are considered as a new generation of large-scale energy-storage devices due to their attractive features of abundant aluminum source, high specific capacity, and high energy density. However, AIBs suffer from a lack of suitable cathode materials with desirable capacity and long-term stability, which severely restricts the practical application of AIBs. Herein, a binder-free and self-standing cobalt sulfide encapsulated in carbon nanotubes is reported as a novel cathode material for AIBs. The resultant new electrode material exhibits not only high discharge capacity (315 mA h g at 100 mA g ) and enhanced rate performance (154 mA h g at 1 A g ), but also extraordinary cycling stability (maintains 87 mA h g after 6000 cycles at 1 A g ). The free-standing feature of the electrode also effectively suppresses the side reactions and material disintegrations in AIBs. The new findings reported here highlight the possibility for designing high-performance cathode materials for scalable and flexible AIBs.

Flexible three-dimensional (3D) nanoarchitectures have received tremendous interest recently because of their potential applications in wearable electronics, roll-up displays, and other devices. The design and fabrication of a flexible and robust electrode based on cobalt sulfide/reduced graphene oxide/carbon nanotube (CoS2 /RGO-CNT) nanocomposites are reported. An efficient hydrothermal process combined with vacuum filtration was used to synthesize such composite architecture, which was then embedded in a porous CNT network. This conductive and robust film is evaluated as electrocatalyst for the hydrogen evolution reaction. The synergistic effect of CoS2 , graphene, and CNTs leads to unique CoS2 /RGO-CNT nanoarchitectures, the HER activity of which is among the highest for non-noble metal electrocatalysts, showing 10 mA cm(-2) current density at about 142 mV overpotentials and a high electrochemical stability.

Novel, porous NiCo2O4 nanotubes (NCO-NTs) are prepared by a single-spinneret electrospinning technique followed by calcination in air. The obtained NCO-NTs display a one-dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO-NT electrode exhibits a high specific capacitance (1647 F g(-1) at 1 A g(-1)), excellent rate capability (77.3 % capacity retention at 25 A g(-1)), and outstanding cycling stability (6.4 % loss after 3000 cycles), which indicates it has great potential for high-performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO-NTs can be attributed to the relatively large specific surface area of these porous and hollow one-dimensional nanostructures.

Rational design and massive production of bifunctional catalysts with superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are essential for developing metal–air batteries and fuel cells. Herein, controllable large‐scale synthesis of sulfur‐doped CaMnO3 nanotubes is demonstrated via an electrospinning technique followed by calcination and sulfurization treatment. The sulfur doping can not only replace oxygen atoms to increase intrinsic electrical conductivity but also introduce abundant oxygen vacancies to provide enough catalytically active sites, which is further demonstrated by density functional theory calculation. The resulting sulfur‐modified CaMnO3 (CMO/S) exhibits better electrocatalytic activity for ORR and OER in alkaline solution with higher stability performance than the pristine CMO. These results highlight the importance of sulfur treatment as a facile yet effective strategy to improve the ORR and OER catalytic activity of the pristine CaMnO3. As a proof‐of‐concept, a rechargeable Zn–air battery using the bifunctional catalyst exhibits a small charge–discharge voltage polarization, and long cycling life. Furthermore, a solid‐state flexible and rechargeable Zn–air battery gives superior discharge–charge performance and remarkable stability. Therefore, the CMO/S nanotubes might be a promising replacement to the Pt‐based electrocatalysts for metal–air batteries and fuel cells.

Designing definite metal-support interfacial bond is an effective strategy for optimizing the intrinsic activity of noble metals, but rather challenging. Herein, a series of quantum-sized metal nanoparticles (NPs) anchored on nickel metal-organic framework nanohybrids (M@Ni-MOF, M = Ru, Ir, Pd) are rationally developed through a spontaneous redox strategy. The metal-oxygen bonds between the NPs and Ni-MOF guarantee structural stability and sufficient exposure of the surface active sites. More importantly, such precise interfacial feature can effectively modulate the electronic structure of hybrids through the charge transfer of the formed Ni-O-M bridge and then improves the reaction kinetics. As a result, the representative Ru@Ni-MOF exhibits excellent hydrogen evolution reaction (HER) activity at all pH values, even superior to commercial Pt/C and recent noble-metal catalysts. Theoretical calculations deepen the mechanism understanding of the superior HER performance of Ru@Ni-MOF through the optimized adsorption free energies of water and hydrogen due to the interfacial-bond-induced electron redistribution.

only retain fl exibility and portability by using suitable electrodes, but also possess excellent electrochemical properties to fulfi l the demand of electricity consumption. Thus, the paramount challenge to fulfi l these requirements is to design fl exible electrodes with robust mechanical strength and large capacitance. [ 8,9 ] Unfortunately, technologies for developing suffi ciently feasible SECs are still largely inadequate. Although, several types of fl exible electrodes based on various carbon substrates and their composites have been reported, [10][11][12] the pursuit of thinner, lighter, and effi cient fl exible SECs has not ceased. More importantly, to realize high-performance fl exible SECs, further enhancement of energy density and operating voltage without compromising the device power density and cycling stability is still urgently required. [ 13 ] An effective strategy is to develop asymmetric solidstate electrochemical capacitors (ASECs), which mostly consist of pseudocapacitive materials and electric double-layer capacitive materials. [14][15][16] One of the most attractive features of ASECs lies in combining different potential windows of two electrodes to increase the device operation voltage (up to 2.0 V), [17][18][19] and thereby signifi cantly improve the energy/power density. Moreover, the electrochemical performance of ASECs is also directly affected by the properties and structures of electrochemical active materials. Therefore, it should be of great scientifi c and technological importance to explore novel fl exible electrodes for ASECs with remarkable capacitance and impressive mechanical sustainability.Pseudocapacitive transition metal oxides (TMOs)/sulfi des such as NiO, [ 13,20 ] Co 3 O 4 , [ 21,22 ] NiCo 2 O 4 , [ 23,24 ] MnO 2 , [ 9,11 ] V 2 O 5 , [25][26][27] and CoS 2 [ 28,29 ] are widely recognized as potential electrode materials for ECs because of their high reversibility during Faradaic reactions and large capacitance. Recent advances in ECs have been motivated by a desire to discover and improve cost-effective TMOs for real applications. As one of the most promising candidates, vanadium pentoxide (V 2 O 5 ) holds great potential because of its low cost, natural abundance, multiple stable oxidation states (V 2+ to V 5+ ), and ease of synthesis. [30][31][32] Moreover, it is well accepted that the electrochemical properties of V 2 O 5 strongly depend on a variety of factors The development of 3D nanoarchitectures on fl exible current collectors has emerged as an effective strategy for preparing advanced portable and wearable power sources. Herein, a fl exible and effi cient electrode is demonstrated based on electrospun carbon fi bers (ECF) substrate with elaborately designed hierarchical porous V 2 O 5 nanosheets (V 2 O 5 -ECF). The unique confi guration of V 2 O 5 -ECF composite fi lm fully enables utilization of the synergistic effects from both high electrochemical performance of V 2 O 5 and excellent conductivity of ECF, endowing the fi lms to be an excellent electrode for ...