Amorphous NiO Research Articles

Amorphous NiO nanopyramids with superior electrochromic energy storage properties

In this work, amorphous NiO nanopyramid film has been obtained by using the pulsed magnetron sputtering technique. The uniform amorphous NiO nanostructures exhibit significant electrochromic modulation efficiency in the visible and near-infrared ranges, achieving a high modulation efficiency of 60.73 % at 550 nm and 21.58 % at 1500 nm. It exhibits rapid response time (coloring takes 2.4 s, and bleaching takes 1.0 s) and significant coloring efficiency (43.23 cm2C-1). Moreover, amorphous NiO nanopyramid film displays promising properties of energy storage. The NiO nanopyramid film shows high areal capacitance (7.08 mF/cm2), along with satisfying rate capability. The alteration in the electrode color offers a convenient method for monitoring the quantity of energy stored. Furthermore, the microstructure characteristic, degree of crystallization and electrochemical performance of the NiO film are significantly influenced by both oxygen partial pressure and sputtering time. These findings highlight the potential of employing this bifunctional amorphous NiO nanopyramid film in diverse advanced nanodevices, encompassing electrochromic energy storage applications with superior performance.

Tailoring the Ni-O Microenvironment in Amorphous-Dominated Highly Active and Stable Zn/NiO for Hydrogen Sulfide Detection.

Amorphous metal oxide semiconductor (MOS) materials are endowed with great promise to modulate electronic structures for gas-sensing performance improvement. However, the elevated-temperature requirement of gas sensors severely impedes the application of amorphous materials due to their low thermal stability. Here, a cationic-assisted strategy to tailor the Ni-O microenvironment in an amorphous-dominated Zn/NiO heterogeneous structure with high thermal stability was developed. It was found that 6 mol % Zn incorporation into amorphous NiO can effectively preserve the amorphous-dominated NiO phase even at high temperature. After calcination, the amorphous oxide can only be converted to crystals partly thus leading to the formation of amorphous/crystalline compounds, and the content of the amorphous phase can be adjusted by changing the calcination temperature. This amorphous/crystalline configuration can induce more electron transfer from Ni to Zn species, leading to the formation of active Niδ+ (δ>2) centers. Ex situ XPS and in situ Raman spectroscopy studies proved that the generated Niδ+ species pronouncedly promote the electron transfer during the H2S adsorption process. The amorphous/crystalline-6 mol % Zn/NiO sensor exhibits exceptional hydrogen sulfide response (2 ppm, 3.23), outstanding repeatability (as long as 5 weeks), and low limit of detection (as low as 50 ppb), surpassing most reported nickel-based gas sensors such as the crystal nickel oxide prepared in this work. The response and detection limit of the latter is only (2 ppm, 1.89) and (0.05 ppm) respectively. Our work thus opens up more opportunities for fundamental understanding and modulating of highly active amorphous sensing materials.

A Coordination-Derived Cerium-Based Amorphous-Crystalline Heterostructure with High Electrocatalytic Oxygen Evolution Activity.

The rational design of heterogeneous catalysts is crucial for achieving optimal physicochemical properties and high electrochemical activity. However, the development of new amorphous-crystalline heterostructures is significantly more challenging than that of the existing crystalline-crystalline heterostructures. To overcome these issues, a coordination-assisted strategy that can help fabricate an amorphous NiO/crystalline NiCeOx (a-NiO/c-NiCeOx) heterostructure is reported herein. The coordination geometry of the organic ligands plays a pivotal role in permitting the formation of coordination polymers with high Ni contents. This consequently provides an opportunity for enabling the supersaturation of Ni in the NiCeOx structure during annealing, leading to the endogenous spillover of Ni from the depths of NiCeOx to its surface. The resulting heterostructure, featuring strongly coupled amorphous NiO and crystalline NiCeOx, exhibits harmonious interactions in addition to low overpotentials and high catalytic stability in the oxygen evolution reaction (OER). Theoretical calculations prove that the amorphous-crystalline interfaces facilitate charge transfer, which plays a critical role in regulating the local electron density of the Ni sites, thereby promoting the adsorption of oxygen-based intermediates on the Ni sites and lowering the dissociation-related energy barriers. Overall, this study underscores the potential of coordinating different metal ions at the molecular level to advance amorphous-crystalline heterostructure design.

Convenient synthesis and enhanced urea oxidation of NiO–CrO@N–C

The NiO–CrO@N–C composite, which was synthesized by amorphous NiO and CrO nanoparticles anchored on an N-containing carbon matrix, presents excellent activity and stability for the electrocatalytic oxidation of urea.

Manipulation of Electron Spins with Oxygen Vacancy on Amorphous/Crystalline Composite-Type Catalyst.

By substituting the oxygen evolution reaction (OER) with the anodic urea oxidation reaction (UOR), it not only reduces energy consumption for green hydrogen generation but also allows purification of urea-rich wastewater. Spin engineering of the d orbital and oxygen-containing adsorbates has been recognized as an effective pathway for enhancing the performance of electrocatalysts. In this work, we report the fabrication of a bifunctional electrocatalyst composed of amorphous RuO2-coated NiO ultrathin nanosheets (a-RuO2/NiO) with abundant amorphous/crystalline interfaces for hydrogen evolution reaction (HER) and UOR. Impressively, only 1.372 V of voltage is required to attain a current density of 10 mA cm-2 over a urea electrolyzer. The increased oxygen vacancies in a-RuO2/NiO by incorporation of amorphous RuO2 enhance the total magnetization and entail numerous spin-polarized electrons during the reaction, which speeds up the UOR reaction kinetics. The density functional theory study reveals that the amorphous/crystalline interfaces promote charge-carrier transfer, and the tailored d-band center endows the optimized adsorption of oxygen-generated intermediates. This kind of oxygen vacancy induced spin-polarized electrons toward boosting HER and UOR kinetics and provides a reliable reference for exploration of advanced electrocatalysts.

Enhanced hydrogen production via urea electrolysis over Ni-NiO electrodeposited on Ti mesh

The sluggish kinetics of anodic oxygen evolution reaction (OER) is regarded as the main bottleneck for ineffective hydrogen production efficiency, limiting the industrial application of electrochemical water splitting. Substituting the OER by urea electrooxidation reaction (UOR) and simultaneously developing highly active and economical bifunctional electrocatalyst for UOR and hydrogen evolution reaction (HER) is a promising method to realize energy-saving hydrogen production and urea-rich wastewater abatement. Herein, self-supporting Ni-NiO film grown on Ti mesh (Ni-NiO/TM) was successfully prepared by a facile cathodic electrodeposition method with using nickel acetate as the only raw material. Electrodeposition process was optimized by modulating the electrodeposition time and potential. x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman characterization revealed the optimized Ni-NiO/TM was comprised of crystalline Ni and amorphous NiO and its morphology exhibited nanosphere structure, assembled by nanosheets. Ni-NiO/TM sample prepared under the potential of −1.5 V and deposition time of 10 min illustrated the lowest UOR potential of 1.34 V at 50 mA cm−2 and robust stability, superior to the recently reported literatures. Furthermore, the HER potential was only −0.235 V to drive the current density of 50 mA cm−2. The cell voltage of urea-assisted electrolysis for hydrogen production in Ni-NiO/TM||Ni-NiO/TM two-electrode system only required 1.56 V to deliver 50 mA cm−2, obviously lower than that (>1.72 V) for overall water splitting. This work demonstrated the potential of Ni-based material as bifunctional electrocatalyst for energy-saving H2 production by urea-rich wastewater electrolysis.

Dry reforming of methane by La2NiO4 perovskite oxide, part I: Preparation and characterization of the samples

One of the research priorities in dry reforming of methane (DRM) technology is the development of highly active and stable catalysts. Using crystalline oxides as catalyst precursors is an effective catalyst optimization scheme for DRM. Therefore, the application of La2NiO4 perovskite in DRM was systematically studied, including preparation, characterization, carbon deposition properties, regeneration properties, and B-site doping, etc. This paper is the first part, the effects of preparation methods (sol-gel, co-precipitation, hydro-thermal, and solid-state methods) on the physicochemical properties and DRM performance of La2NiO4 samples were investigated, and the relationship between materials' structure and their catalytic performance was analyzed. The results showed that compared with the samples prepared by the hydro-thermal and co-precipitate methods, the sample prepared by the sol-gel method exhibited the highest conversion of CH4 and CO2 (91.4% and 91.5%, respectively) and the best carbon resistance in DRM, which were mainly attributed to its richer microstructure, higher reducibility and basicity. While the lowest DRM performance of the sample prepared by the solid-state method was mainly due to the small amount of reduced amorphous NiO and the weak reducibility of the perovskite phase in this sample, resulting in the inability of perovskite in-situ decomposition under the DRM atmosphere.

Integrating Electrochemical CO2 Reduction on α-NiS with the Water or Organic Oxidations by Its Electro-Oxidized NiO(OH) Counterpart to an Artificial Photosynthetic Scheme

Efficient hydrogen production, biomass up-conversion, and CO2-to-fuel generation are the key challenges of the present decade. Electrocatalysis in aqueous electrolytes by choosing suitable transition-metal-based electrode materials remains the green approach for the trio of sustainable developments. Given that, finding electrode materials with multifunctional capability would be beneficial. Herein, the nanocrystalline α-NiS, synthesized solvothermally, has been chosen as an electrode material. As the first step to construct an electrolyzer, α-NiS deposited on conducting nickel foam (NF) has been used as an anode, and under the anodic potential, the α-NiS particles have lost sulfides to the electrolyte and transform to amorphous electro-derived NiO(OH) (NiO(OH)ED), confirmed by different spectroscopic and microscopic studies. In situ transformation of α-NiS to amorphous NiO(OH)ED results in an enhancement of the electrochemical surface area and not only becomes active toward oxygen evolution reaction (OER) at a moderate overpotential of 264 mV (at 20 mA cm-2) but also can convert a series of biomass-derived organic compounds, namely, 2-hydroxymethylfurfural (HMF), 2-furfural (FF), ethylene glycol (EG), and glycerol (Gly), to industrially relevant feedstocks with a high (∼96%) Faradaic efficiency. During these organic oxidations, NiO(OH)ED/NF participate in the multiple-electron oxidation process (up to 8e-) including C-C bond cleavages of EG and Gly. During the cathodic performance of the α-NiS/NF, the structural integrity has been retained and the unaltered α-NiS/NF electrode remains more effective cathode for alkaline hydrogen evolution reaction (HER) and CO2 reduction (CO2R) compared to its in situ-derived NiO(OH)ED/NF. α-NiS/NF can reduce the CO2 predominantly to CO even at a higher potential like -0.8 V (vs RHE). The fabricated cell with α-NiS and its electro-oxidized NiO(OH)ED counterpart, α-NiS/NF(-)/(+)NiO(OH)ED/NF, is able to show an artificial photosynthetic scheme in which the NiO(OH)ED/NF anode oxidizes water to O2 and the α-NiS cathode reduces CO2 majorly to CO in a moderate cell potential. In this study, α-NiS has been utilized as a single electrode material to perform multiple sustainable transformations.

Facile Synthesis of Amorphous NiO/Reduced Graphene Oxide as a Cocatalyst for Enhanced Dye-Sensitized Photocatalytic H2 Evolution

It is still a challenge to develop efficient catalysts for hydrogen evolution reaction (HER) via a low-cost and simple method. Herein, we report an amorphous NiO/reduced graphene oxide (A-NG) composite as a cocatalyst for enhanced photocatalytic H2 evolution via dye sensitization. The A-NG composite is facilely fabricated by calcinating the NiCl2/GO precursor at a low temperature of 250 °C. The detailed characterizations show that amorphous NiO presents as tiny nanoparticles highly dispersed on graphene sheets, and nickel carbide is formed at the NiO/graphene interface, which demonstrates the strong interaction between Ni and the defective carbon of graphene. Compared with crystalline NiO/rGO (C-NG), the A-NG cocatalyst shows much enhanced dye-sensitized photocatalytic HER activity because the amorphous NiO nanoparticles can effectively adsorb the dye. As a result, highly dispersed amorphous NiO accelerates the photoinduced electron transfer from the excited dye to the cocatalyst, namely, the amorphous nickel carbide formed between NiO and rGO. This work provides a low-cost and simple method to develop efficient cocatalysts for photocatalytic H2 evolution.

High frequency resistive switching behavior of amorphous TiO2 and NiO

Resistive switching (RS) of Transition Metal Oxides (TMOs) has become not only an attractive choice for the development of next generation non-volatile memory, but also as a suitable family of materials capable of supporting high-frequency and high-speed switching needed for the next generation wireless communication technologies, such as 6G. The exact mechanism of RS is not yet clearly understood; however, it is widely accepted to be related to the formation and rupture of sub-stoichiometric conductive filaments (Magnéli phases) of the respective oxides upon activation. Here, we examine the switching behaviour of amorphous TiO2 and NiO both under the DC regime and in the high frequency mode. We show that the DC resistance of amorphous TiO2 is invariant of the length of the active region. In contrast, the resistance of the NiO samples exhibits a strong dependence on the length, and its DC resistance reduces as the length is increased. We further show that the high frequency switching characteristics of TiO2, reflected in insertion losses in the ON state and isolation in the OFF state, are far superior to those of NiO. Fundamental inferences stem from these findings, which not only enrich our understanding of the mechanism of conduction in binary/multinary oxides but are essential for the enablement of widespread use of binary/multinary oxides in emerging non-volatile memory and 6G mm-wave applications. As an example of a possible application supported by TMOs, is a Reflective-Type Variable Attenuator (RTVA), shown here. It is designed to operate at a centre frequency of 15 GHz. The results indicate that it has a dynamic range of no less than 18 dB with a maximum insertion loss of 2.1 dB.

Constructing Multiple Heterostructures on Nickel Oxide Using Rare‐earth Oxide and Nickel as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

AbstractConstructing heterostructured electrocatalyst is a promising strategy to explore inexpensive and effective catalysts towards oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and the overall water splitting (OWS). Here, amorphous NiO 2D layers decorated with Ni and rare earth oxide (REOx) nanoparticles, which possess multiple heterostructures (Ni−NiO and REOx‐NiO), have been synthesized by the sequential electrodeposition on carbon cloth. The electrocatalytic performances for the prepared Er2O3/Ni−NiO and CeO2/Ni−NiO have been evaluated, exhibiting improved HER (39 mV@10 mA cm−2) and OER (318 mV@50 mA cm−2) activities in contrast to the single component, respectively. Additionally, the two‐electrode system (Er2O3/Ni−NiO//CeO2/Ni−NiO) presents an excellent OWS property which displays a low potential of 1.58 V to reach 10 mA cm−2. This work helps to deepen the understanding of the synergetic interaction between dissimilar materials in heterostructured catalyst, and provides guidance for the further exploration and evolution of nanomaterials in green energy conversion technology.

Short-range order in amorphous nickel oxide nanosheets enables selective and efficient electrochemical hydrogen peroxide production

Achieving high selectivity and activity with the oxygen reduction reaction (ORR) is significant for developing efficient energy conversion techniques and chemical production. Here, we report that selective ORRs can be achieved by tuning short-range order in amorphous and crystalline NiO nanosheets (a-NiO NSs and c-NiO NSs, respectively). X-ray absorption spectroscopy analysis reveals that the short-range order of a-NiO NSs and c-NiO NSs mainly adopt the NiO5 pyramidal and NiO6 octahedral structures, respectively. The a-NiO NSs for electrochemical H2O2 production in 0.1 M KOH exhibits both high selectivity over 90% and high activity (1 mA cm−2 at 0.66 V versus RHE), while c-NiO NSs tends to catalyze ORRs through 4-electron pathways to generate H2O. Theoretical calculations indicate that the changed short-range order of a-NiO NSs leads to alteration of Ni d-orbital states, which can regulate the adsorption orientation and strength of ∗OOH intermediates to achieve high selectivity and activity of 2-electron ORRs.

SiO2@NiO core/ shell nanoparticles as high-performance anode materials: Synthesis and characterizations of structural, optical and magnetic properties

In this paper, synthesis and structural and optical properties of the SiO2 @ NiO core-shell nanostructures were studied. The SiO2 and NiO nanoparticles and SiO2@NiO core/shell nanoparticles were prepared by co-precipitation and chemical reduction method using the two different agents of functionalized silica and non-functionalized silica. The XRD analysis showed that SiO2 nanoparticles have an amorphous structure and NiO nanoparticles have a cubic structure. The XRD analysis of SiO2@NiO core/shell nanoparticles showed the presence of nickel oxide phase and silica amorphous phase as well as a background of silica nanoparticles. The morphology of SiO2@NiO core/shell nanoparticles by Scanning Electron Microscopy (SEM), shows form of spherical core with a coating of NiO and it was confirmed by transmission electron microscopy (TEM) analysis. Also, the diameter of these nanoparticles was about 125 ± 5 nm as a halo (shell) of NiO nanoparticles on spherical silica nanoparticles The UV-Vis spectroscopic studies showed that the energy gap of the SiO2@NiO core/shell nanoparticles varied in the range of 3.80 – 4.20 eV. The results of the magnetization experiment (VSM) of the samples showed the soft ferromagnetic structure for the nickel oxide nanoparticles and the paramagnetic structure for the SiO2@NiO core shell nanoparticles. Finally, the Fourier transform infrared (FTIR) spectrum confirmed the formation of SiO2-H, NiO-H and Ni-O bonds in core-shell nanostructures. It can be expected that these nanostructures are suitable as high-performance anode materials in various types of fuel batteries, including lithium batteries.

A surface-nitridized 3D nickel host for lithium metal anodes with long cycling life at a high rate.

Three dimensional (3D) metal structures such as nickel (Ni) and copper (Cu) frames have long been regarded as a good host for lithium (Li) metal. However, Li deposition on different metals often causes obvious over-potential, affecting the electrode performance in lithium metal batteries. Here, a Ni-N-O interface was created by surface nitridation to the Ni micro-particles, which were made into 3D current collectors. The directly grown Ni3N created a thin and lithiophilic layer containing dense Li nucleation sites. The homogeneous distribution of amorphous Ni3N and NiO at the interface allowed for a fast transfer of both electrons and ions, and thus facilitated smooth and even plating/stripping of lithium. High cycling stability and rate capability were simultaneously achieved. The 3D Li@N-Ni anode exhibited an extremely low voltage hysteresis of ∼10 mV over 850 h in a symmetric cell. The full battery paired with LiFePO4 achieved steady cycling at 5C for 1500 cycles, with coulombic efficiency constantly higher than 99.2% and an average capacity loss of 0.027 mA h g-1 per cycle, demonstrating a rational strategy for the design and fabrication of efficient lithium anodes for practical applications.

Atomistic insights into the protection failure of the graphene coating under the hyperthermal impacts of reactive oxygen species: ReaxFF-based molecular dynamics simulations

ReaxFF-based molecular dynamics was used to demonstrate the limited coating effect of pristine graphene in protecting a typical Ni(111) substrate against hyperthermal oxygen species. Under 10-eV O2 and O3 molecules, graphene remained intact, and served as a protective coating by preventing the diffusion of molecules towards underlying Ni(111). By increasing the initial energy of incident species to 20 and 30 eV, graphene failed to provide efficient protection, offering protection degrees of 53.16 and 40.87% against O2, and 55.12 and 47.78% against O3. As opposed to O2 and O3, 10-eV O exposure led to a low protection degree of 58.95%, decreasing to 21.98%, and switching to 6.20% anti-protection when the initial energy increased to 20 and 30 eV. Through the detailed analysis of simulated trajectories, a three-stage oxidation process was proposed, elucidating the mechanism for these low protection degrees. On the basis of the proposed mechanism, the graphene’s coating effect is limited by the formation and growth of defects on graphene, enabling atomic diffusion across the graphene-Ni(111) interface, and leading to NiO formation over the damaged regions of graphene. The structural analysis then confirmed graphene’s transformation from a crystalline to a highly disordered carbon phase decorated by an amorphous NiO phase.

Sequential Electrodeposition of Bifunctional Catalytically Active Structures in MoO3 /Ni-NiO Composite Electrocatalysts for Selective Hydrogen and Oxygen Evolution.

Exploring earth-abundant and highly efficient electrocatalysts is critical for further development of water electrolyzer systems. Integrating bifunctional catalytically active sites into one multi-component might greatly improve the overall water-splitting performance. In this work, amorphous NiO nanosheets coupled with ultrafine Ni and MoO3 nanoparticles (MoO3 /Ni-NiO), which contains two heterostructures (i.e., Ni-NiO and MoO3 -NiO), is fabricated via a novel sequential electrodeposition strategy. The as-synthesized MoO3 /Ni-NiO composite exhibits superior electrocatalytic properties, affording low overpotentials of 62 mV at 10 mA cm-2 and 347 mV at 100 mA cm-2 for catalyzing the hydrogen and the oxygen evolution reaction (HER/OER), respectively. Moreover, the MoO3 /Ni-NiO hybrid enables the overall alkaline water-splitting at a low cell voltage of 1.55 V to achieve 10 mA cm-2 with outstanding catalytic durability, significantly outperforming the noble-metal catalysts and many materials previously reported. Experimental and theoretical investigations collectively demonstrate the generated Ni-NiO and MoO3 -NiO heterostructures significantly reduce the energetic barrier and act as catalytically active centers for selective HER and OER, synergistically accelerating the overall water-splitting process. This work helps to fundamentally understand the heterostructure-dependent mechanism, providing guidance for the rational design and oriented construction of hybrid nanomaterials for diverse catalytic processes.

Charge reactions on crystalline/amorphous lanthanum nickel oxide cocatalyst modified hematite photoanode.

Understanding the charge reactions at the semiconductor/cocatalyst interface is of great interest for boosting photoelectrochemical water splitting since the charge transfer to water molecules is the sluggish one. Besides the dopants, porosity, or ion-penetration of the cocatalyst, the crystallinity of the cocatalyst may also influence the charge reactions at the interface. Herein, we prepared amorphous LaNiOx and crystalline La-doped NiO (c-LaNiOx) cocatalysts through photochemical decomposition and ion-exchange of Ni(OH)2 precipitation, respectively. Both lanthanum nickel oxides (LaNiOx) showed considerable improvement of hematite photoanodes. By using electrochemical impedance measurements, we confirmed that the catalyst could store photogenerated charges with reduced transfer resistance and passivate the surface state, resulting in the overall charge transfer rate enhancement. This study may lead to a chance to uncover the kinetic bottleneck with an efficient cocatalyst in well-controlled crystallinity in the future.

A Facile Topochemical Preparation of Ni-Fe LDH Nanosheets Array on Nickel Foam Using In Situ Generated Ni2+ for Electrochemical Oxygen Evolution

Herein, we presented a simple one-step method to prepare Ni-Fe layer double hydroxide nanosheets array (Ni-Fe LDH NSA) integrated electrodes under anaerobic condition at room temperature using untreated nickel foam (NF) as substrate and the NiO thin layer thereon as the Ni2+ source. FeSO4 is utilized as Fe source. The amorphous NiO layer on NF can be dissolved in the weak acidic Fe2+ solution. NH4HCO3 is added to adjust the pH value for controlled hydrolysis of Ni2+ and Fe2+ became brucite to LDH after exposed on the air. Fe-O-Fe and Ni-O-Fe moieties can be lead in during this facile topochemical preparation of Ni-Fe LDH. The structure of electrodes was characterized by SEM, TEM, XPS, XRD, etc. The OER performance of the integrated electrode was tested by a series of electrochemical measurement. The prepared integrated electrode Ni-Fe LDH/NF shows good OER performance with relatively low overpotential (198 mV at 10 mA cm−2), moderate tafel slope (70 mV dec−1) and high electrochemical stability.

Nickel Ammine Complex‐derived NiO Modified g‐C3N4 Composites with Enhanced Visible‐light Photocatalytic H2 Evolution Performance

AbstractIn this paper, NiO/g‐C3N4 (NiO/CN) composites were successfully prepared by the wetness impregnation method using nickel ammine complex solution as NiO source. As photocatalysts, NiO/CN composites showed enhanced visible‐light photocatalytic hydrogen evolution activities in the presence of triethanolamine as sacrificial agent. The effects of NiO content and annealing temperature for NiO/CN composites on the photocatalytic H2 evolution activities were investigated. Furthermore, NiO/CN composite with 10.0% NiO content after annealing at 450 °C exhibited optimal photocatalytic H2 evolution rate of 90.05 μmol⋅h−1⋅g−1 which is about 17 times higher than that of pristine CN (5.22 μmol⋅h−1⋅g−1). Moreover, the experimental results demonstrated that amorphous NiO as co‐catalyst not only offered active sites for H2 evolution but also benefited the efficient separation of the photogenerated charge carries. In addition, NiO/CN composite displayed the superior photocatalytic stability during the photocatalytic process.

Na0.11WO3 nanoflake arrays grown on Ni foam for high-performance supercapacitor

Via a facile one-pot hydrothermal method, nanoflake arrays constructed by Na0.11WO3 and amorphous NiO or Ni (OH)2 were successfully grown on Ni foam (NF) in the presence of urea. The correlation between synthetic condition, composition, morphology and electrochemical behavior of the obtained compounds has been investigated. The optimum sample, Na0.11WO3/NF-15 (urea/Co molar ratio = 15) shows a large volumetric capacity of 14.86 and 6.00 C cm−3 at 0.5 and 10 mA cm−2 (3.33 and 66.67 mA cm−3), respectively, which is related with the three-dimensional (3D) W-O-W host framework of Na0.11WO3 with good electron conductivity, providing open tunnel for alkali ions to be intercalated/deintercalated. On the other hand, it is associated with the heterostructure of Na0.11WO3 and NiO or Ni (OH)2, giving to synergistic effect. Furthermore, it is ascribed to the 3D porous nanoflake arrays vertically grown on Ni foam. As a result, active sites can be exposed to electrolyte ions effectively. Meanwhile, Na0.11WO3/NF-15//activated carbon asymmetric supercapacitor can deliver a maximum energy density of 2.13 mWh cm−3 at the power density of 2.40 mW cm−3 with 87.5% of capacity retention after 10,000 charging-discharging cycles at 50 mA cm−2 (333.33 mA cm−3).