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Owing to their superb mechanical durability resulting from the dramatic volume changes of the Sn nanoparticles and high electrical conductivity, carbon and tin (Sn) nanocomposites have received an increasing attention in view of their application as anode materials for lithium ion batteries (LIBs). However, due to the poor ionic diffusion capability for Li ions during the cycling, the low ultrafast performance for energy storage remains rather limited. In the present study, aiming to improve the ionic diffusion capability for Li ions, we suggest a novel design of the debossed structure of carbon and Sn nanocomposites by electrospinning, carbonization, and the debossing process. The electrode based on the debossed structure exhibits a noticeable cycling stability and high discharge capacity (677 mA h g−1 after 100 cycles at 100 mA g−1), an excellent rate capability (482 mA h g−1 at 2000 mA g−1), and an outstanding ultrafast cycling stability (275 mA h g−1 after 500 cycles at 2000 mA g−1). Therefore, this novel design of the debossed structure based on carbon and Sn nanocomposites offers attractive effects, such as the effective accommodation of dramatic volume changes for the Sn nanoparticles, as well as an improved ionic diffusion performance of Li ions.

Carbon has acquired considerable attention in view of its application as supports for platinum (Pt) catalyst in direct methanol fuel cells (DMFCs) with promising renewable energy source due to their high surface area and excellent chemical stability. However, the progress of carbon supports still needs to move towards the practical utilization of high-performance DMFCs. In the present study, we propose a novel support of nitrogen (N)-doped carbon and nickel (Ni) composites produced from protein using an impregnation process and carbonization to increase the electrical conductivity. To this end, we fabricated the Pt nanoparticles on N-doped carbon and Ni composites (Pt@NC/Ni). To obtain the optimized electrochemical performance, the amount of Ni components into carbon supports was controlled by three types. Specifically, as compared to commercial Pt/C and other samples, the optimized Pt@NC/Ni with the high electrical conductivity of 0.75 S cm−1 shows the lowest onset potential of 0.03 V, the highest anodic current density of 744 mA mgPt−1, and an excellent catalytic stability with the highest retention rate of 86%. Accordingly, this novel support provides multiple advantages in terms of the well-dispersed Pt nanoparticles on the surface, N-doping effect of carbon supports, and an increased electrical conductivity by the introduction of Ni components. Therefore, Pt@NC/Ni is a promising novel catalyst to enhance electrochemical performance of methanol oxidation reaction.

Owing to the characteristics of high energy density, low operating temperature, and environmentally-friendly features, direct methanol fuel cells (DMFCs) are a promising renewable energy source. However, the electrocatalysts of the anode are vulnerable in terms of their electrochemical performance, as they can be easily toxified by CO and other hydrocarbons, which might lead to a break-up of the methanol oxidation reaction (MOR). For further advances in the DMFC industry with improved electrochemical performance, this issue should be urgently resolved. Thus, this study proposes a novel approach to synthesize protein-based carbon as platinum electrocatalyst supports (PCPs) from tofu using a carbonization for the improved methanol oxidation activities. Among commercial Pt/C and other samples, the composite loaded 10 wt% Pt electrocatalyst showed the highest anodic current density of 510 mA mgPt−1, the excellent electrocatalytic stability, and the highest retention of 86%. The improved electrochemical performances can be attributed to the good dispersion of Pt electrocatalysts and N-doping effect of protein-based carbon supports. These results suggest that PCPs derived from tofu will be one of promising candidates as platinum catalyst supports to improve methanol oxidation activities.

We prepare granule Li4Ti5O12/carbon nanotube composite (LTO/CNT) using intermediate Li2TiO3 and then used as an anode of hybrid supercapacitors. The hybrid supercapacitors fabricated with LTO/CNT anode with 3 wt% CNT and activated carbon (AC) cathode deliver superior electrochemical performances. It is mainly ascribed to the reduced charge-transfer resistance and improved ionic and electronic conductivity, resulting from smooth and rapid lithium ion kinetics and electron diffusion by suppression of particle growth and aggregation. Moreover, elastic properties of CNT can alleviate the volume change of LTO during charge-discharge process, resulting in excellent cycle performance. The performance improvement such as discharge capacitance, rate capability, and cyclability as well as energy and power density demonstrate that 3 wt% CNT addition in LTO anode appeal for high performance hybrid supercapacitors.

The design of a low-cost, stable, and highly efficient electrocatalyst using a non-precious material and carbon composites for oxygen reduction reaction (ORR) activity to replace platinum-based electrocatalyst is essential for future energy conversion devices, such as fuel cells and metal air batteries. However, previous efforts to acquire the high ORR activity by non-precious material and carbon composites faced substantial challenges due to a few active sites during electrochemical reactions. Herein, we synthesize an advanced composite of iron carbide nanoparticles on nitrogen and cobalt-doped carbon nanofiber (Fe3C/N@Co-doped CNF) by electrospinning, a precures coating process and carbonization. Fe3C/N@Co-doped CNF offers a high onset potential of 0.9 V, high half-wave potential (E1/2) potential of 0.8 V, and a nearly four-electron pathway (n = 3.9). Therefore, this unique composite provides multi-active sites using the doping system and metal carbide nanoparticles for the ORR activity, as well as an outstanding tolerance to methanol crossover.

In the present study, in order to demonstrate the one-pot synthesis of aluminum oxide (Al 2 O 3 ) coating and aluminum doping, we synthesized aluminum oxide (Al 2 O 3 )-coated LiAl x Mn 2-x O 4 (LAMO) NPs using a sequential process of the as-spun nanofiber templates, chemical precipitation, and calcination as a cathode material in lithium ion batteries (LIBs). To find the optimum condition of Al 2 O 3 coating layer and Al doping, we performed the simple calcination methods at 300 °C using the Al(OH) 2 -coated LMO NPs. The resultant Al 2 O 3 -coated LAMO NPs exhibited the highest capacity of 111.1 mAh g −1 with the capacity retention of 94.4% after 90 cycles at 1 C, excellent rate performance, and the highest high-rate capacity of 81.4 mAh g −1 at 10 C as compared to bare LMO NPs without Al 2 O 3 coating and Al(OH) 2 -coated LMO NPs without calcination. The improved electrochemical performance can be defined by the co-effect of Al 2 O 3 coating and Al doping on bare LMO NPs. The former is related to cycle stability that increased due to the prevention of volume expansion and Mn dissolution as a physical buffer layer. The latter is related to high-rate performance improved due to the enhanced bonding energy of Al O bond. Therefore, it can be concluded that Al 2 O 3 -coated LAMO NPs are promising candidate cathode materials for high-performance LIBs.

Interface engineering of LiMn2O4 (LMO) is a promising strategy to enhance the lithium storage capability and cycling stability of cathode materials in Li-ion batteries (LIBs). This is because the strategy prevents structural degradation; however, Li storage kinetics remains unsatisfactory, resulting in poor ultrafast cycling performance. Therefore, we fabricated an Nb-doped TiO2 (NTO) functional layer as a conductive passivation layer on the LMO surface by horizontal ultrasonic spray pyrolysis deposition. The NTO functional layer suppressed the volume expansion of LMO and exhibited high electrical and ionic conductivity, which resulted in improved structural stability of LMO (related to cycling stability) and increased electron/ion transfer rate (related to ultrafast cycling performance). In the TiO2 structure, Ti4+ ions were replaced by Nb5+ ions, which possess high electrical conductivity and a wide c-axis as a Li-ion diffusion route. As a result, the NTO-coated LMO cathode material showed an outstanding specific capacity of 112.7 mAh/g with a remarkable capacity retention of 96.2% after 100 cycles at a current density of 1 C and excellent ultrafast cycling capacity and stability of 70.0 mAh/g after 500 cycles at a current density of 10 C.

Carbon materials as intra-electrode frameworks for energy storage devices have received noticeable attention due to their high porosity, high electrical conductivity, and excellent chemical and physical stability. Nevertheless, the utilisation of these frameworks still faces significant challenges such as limited raw material resources, complicated synthetic process, high-temperature synthesis, and high production costs. Herein, we report a unique and facile approach to synthesise a spoilt tofu-derived carbon framework with embedded ultrasmall Sn nanocrystals (SCS) derived from food waste (such as spoilt tofu) using simple impregnation and carbonisation. The unique architecture of SCS was due to the porous structure of spoilt tofu and was utilised as an anode for Li-ion batteries. The optimised SCS architecture shows excellent electrochemical performance with outstanding cycling stability (621 mA h g −1 capacity retention up to 100 cycles) and excellent high-rate performance (250 mA h g −1 at 2000 mA g −1 ). Thus, this facile approach provides helpful synergistic effects in terms of structural stability, electrochemical active surface area, and shorter diffusion pathways for Li ions. Consequently, the recycling strategy of spoilt tofu food waste could provide a unique route to low-cost production of high-performance Li-ion batteries.

Silicon and carbon composites as an anode material in lithium-ion batteries are the most promising candidates to replace conventional graphite, owing to their synergetic effects of high capacity and excellent mechanical stability. Despite these appealing merits, the significant challenge is directly related to the poor dispersion of Si nanoparticles in the carbon nanofiber (CNF) matrix, leading to a structural collapse after cycling due to the large volume change (∼300%) of Si. Thus, we synthesized unique composites of high-dispersed Si and titanium oxide (TiO2) nanoparticles in the CNF matrix (Si/TiO2/CNF) using the complexation of TiO2 nanoparticles in order to the high-dispersed Si nanoparticles. The Si/TiO2/CNF electrode presents enhanced electrochemical properties including excellent cycling stability and high specific capacity (947 mA h g−1 at 100 mA g−1 after 100 cycles), remarkable high-rate performance (612 mA h g−1 at 2000 mA g−1), and outstanding ultrafast cycling stability (478 mA h g−1 at 2000 mA g−1 after 100 cycles). It is revealed that the high-dispersed Si nanoparticles can maintain the initial structure after cycling, which definitely demonstrates the superiority of our concept.

To improve the electrochemical performance of hybrid capacitors, hollow lithium manganese oxide (LiMn 2 O 4 , LMO) nanotubes (NTs) as cathode materials were synthesized by a solid-state reaction, using MnO 2 coated on a porous carbon nanofiber (PCNF) templates. To determine the optimum shell thickness of hollow LMO, the time of MnO 2 coating on PCNF was adjusted to 10, 30, and 60 min. Among these, hollow LMO NTs, which were synthesized by 30-min coating with MnO 2 on the PCNFs, have superior performance. They exhibited an excellent reversible capacity (∼72.8 mAh g −1 ) at 1 C, capacity retention of ∼98.4% after 100 cycles, and an excellent high-rate capability. This superior performance can be explained by the hollow structure giving a reduced diffusion distance for Li-ions, the networked structure of one-dimensional NTs allowing fast charge transfer, and the achievement of the optimal stoichiometric ratio of the LMO phase.

As effective and simple approach by which to construct hybrid nanocomposite using ZnS nanoparticles (NPs) and conducting carbon materials to realize robust ultrafast lithium storage capabilities, we newly developed tunneled-mesoporous S-doped carbon nanofibers (SCNF) embedded with ZnS NPs through a one-pot carbonization process via the thiourea effect. This hybrid nanocomposite is unique given its tunneled-mesoporous CNF structure with well-dispersed ZnS NPs by ZnO sulfurization, offering available space to accept abrupt structural expansions of ZnS NPs and efficient Li-ion pathways during the electrochemical reaction. Using this material leads to competitive cycling stability and superior rate capabilities. Even at a high current density of 2000 mA g−1, amazing ultrafast electrochemical performance outcomes with a high specific capacity (391.8 mAh g−1) and good long-term cycling stability (97.2%) after 500 cycles were noted. These findings are attributed to the synergistic effects of the accelerated the transportation of Li ions for the ZnS NPs by the internal construction of the tunneled-mesoporous SCNF and facilitation of the electrical conductivity of the electrode via the S doping effect of the CNF matrix. Therefore, the proposed approach for a unique hybrid nanocomposite holds great potential regarding the development of an outstanding anode electrode to enhance the ultrafast lithium storage capabilities.

Well-dispersed Fe nanoparticles exposed within N-doped mesoporous carbon nanofibers (Fe−NMCNF) are synthesized using electrospinning and H 2 -activation. Their morphologies, crystal structures, chemical bonding states, and electrochemical performance are demonstrated at three calcination temperatures (700, 800, and 900 °C) during H 2 -activation. Fe−NMCNF calcined at 800 °C had a high specific surface area of 467.6 m 2 g −1 , total pore volume of 0.88 cm 3 g −1 , large average pore size of 7.5 nm, and large mesopore volume fraction of 79.1%. In particular, the Fe−NMCNF sample calcined at 800 °C exhibits both excellent catalytic activity for oxygen reduction reaction and superb long-term stability compared to commercial Pt/C in acid electrolyte of 0.1 M HClO 4 . The performance improvement results from the combined effect of the well-dispersed Fe nanoparticles exposed within N-doped mesoporous CNFs and the uniform morphology of mesoporous CNFs.

Octahedral Co3O4/carbon nanofibers (CNFs) composite-supported Pt catalysts are synthesized using electrospinning, hydrothermal, and reduction methods in sequence, and their structure, chemical bonding states, and electrochemical properties are investigated. To obtain the optimal support, the relative molar ratio of the Co precursor to the solution was adjusted to three different levels: 0.05 M (sample A), 0.1 M (sample B), and 0.2 M Co precursor (sample C). Sample B exhibited the highest electrocatalytic activity of ∼415.6 mA mgpt−1 and superb electrocatalytic stability compared to commercial Pt/C, Pt/conventional CNFs, sample A, and sample C. This performance improvement can be explained by the combined effects of optimally sized octahedral Co3O4 on the CNF matrix, resulting in the maximum dispersion of Pt catalysts, and the formation of Co(OH)2 phases, which hinder CO poisoning.

Al-doped ZnO (AZO)/Ag grid hybrid transparent conductive electrode (TCE) structures were fabricated at a low temperature by using electrohydrodynamic jet printing for the Ag grids and atomic layer deposition for the AZO layers. The structural investigations showed that the AZO/Ag grid hybrid structures consisted of Ag grid lines formed by Ag particles and the AZO layer covering the inter-spacing between the Ag grid lines. The Ag particles comprising the Ag grid lines were also capped by thin AZO layers, and the coverage of the AZO layers was increased with increasing the thickness of the AZO layer. Using the optimum thickness of AZO layer of 70 nm, the hybrid TCE structure showed an electrical resistivity of 5.45 × 10 −5 Ω cm, an optical transmittance of 80.80%, and a figure of merit value of 1.41 × 10 −2 Ω −1 . The performance enhancement was suggested based on the microstructural investigations on the AZO/Ag grid hybrid structures.

We report on the fabrication and magnetic properties of Fe-doped In 2 O 3 /α-Fe 2 O 3 core/shell nanofibers (NFs) by co-electrospinning method. The structural investigations showed that the core and shell materials were composed of crystalline Fe-doped In 2 O 3 NFs and α-Fe 2 O 3 nanoparticles with a size of less than 1 μm, respectively, and the morphologies of the resultant NFs changed with variation of the relative source ratio of In to Fe (the In/Fe molar ratio). Interestingly, X-ray diffraction and X-ray photoelectron spectroscopy results showed that the Fe elements were incorporated into the In 2 O 3 lattice, causing a modification of the magnetic properties of the In 2 O 3 /α-Fe 2 O 3 core/shell NFs. Investigations of the magnetic properties of the core/shell NFs showed enhanced magnetic properties, and an increase in saturation magnetization values with an increased In/Fe molar ratio. Based on our results, we suggest three mechanisms for the enhancement of magnetic properties that result from our proposed structures.

We synthesized RuO 2 –Ag 2 O composite nanowires by means of an electrospinning method and investigated the capacitance, high-rate performance, and cycle number dependence of the composite nanowire electrodes. In order to synthesize optimum RuO 2 –Ag 2 O composite nanowires, the relative mole ratio of Ag precursor to Ru precursor varied from ∼0.1 to ∼0.3. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy results show that crystalline RuO 2 –Ag 2 O composite nanowires (∼40–70 nm in diameter) are formed upon calcinations. Cyclic voltammetry results show that among the samples, the RuO 2 –Ag 2 O composite nanowires fabricated with the mole ratio of ∼0.2 give the highest capacitance, excellent high-rate performance, and excellent retention of capacity (∼97%).

We report on the formation and electrochemical properties of Co 3 O 4 /Pt nanocomposite electrodes, which were fabricated by an RF magnetron co-sputtering system, for micro-electrochemical capacitors. High-resolution electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy examinations are performed to characterize the structural and chemical properties of the Co 3 O 4 /Pt nanocomposite electrodes. It is shown that the Co 3 O 4 /Pt6020 nanocomposite electrodes where RF powers of 60 and 20 W were applied to Co 3 O 4 and Pt targets, respectively, give capacitance of 391.6 F/cm 3 at 100 mV/s along with superb high-rate performance, which is much higher that those of Co 3 O 4 only and other nanocomposite electrodes. The improvement is explained in terms of the formation of Co 3 O 4 –Pt combined nanostructures and their good electrical conductivity.

We fabricated three types of nanocomposite electrodes consisting of different amounts of metallic Pt nanostructures and amorphous CeO 2 using a co-sputtering method and investigated the optimum conditions for enhancing their electro-oxidation properties in direct methanol thin-film fuel cells. The high-resolution electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy results show the formation of metallic Pt nanostructures embedded within an amorphous CeO 2 matrix (i.e., Pt–CeO 2 nanocomposite). The cyclic voltammetry and chronoamperometry results demonstrate that the nanocomposite electrode containing ∼87.2 wt% of Pt shows the best catalytic activity of methanol electro-oxidation, the highest electrochemical active surface (EAS) area, and the best electrochemical stability among the three samples for direct methanol thin-film fuel cells.

We investigated the catalytic activity of Pt-incorporated CuO electrodes for thin-film fuel cells. The electron microscopy and X-ray diffraction results show the formation of Pt nanoparticles embedded within an amorphous CuO matrix (Pt–CuO nanocomposite). The Pt–CuO nanocomposite electrode gives a much higher current density than a Pt only electrode at an accelerating voltage of 0.67 V in a mixture of 2.0 M CH3OH and 0.5 M H2SO4 solutions. The enhanced catalytic activity of the nanocomposite electrode is attributed to the increased active surface area, due to the formation of Pt nanoparticles, and the amorphous CuO supporting matrix.