Cobalt/Nickel Ions-Assisted Synthesis of Laminated CuO Nanospheres Based on Cu(OH)2 Nanorod Arrays for High-Performance Supercapacitors

Cu2S/C@NiMnCe-layered double hydroxide with core-shell rods array structure as the cathode for high performance supercapacitors

The selection of highly efficient materials and the construction of advantageous structures are essential for realizing high-performance electrode materials. In this paper, electrode material Cu2S/C@NiMnCe-LDH/CF with excellent morphology and high performance has been successfully designed and prepared by simple hydrothermal and calcination techniques. First, ZIF-67 is loaded on the outer layer of Cu2S rods to obtain core-shell structured Cu2S@ZIF-67 rods, whose ZIF-67 MOF shell is carbonized to obtain Cu2S@C rods. Then, NiMnCe-LDH are epitaxially loaded on the outer layer of Cu2S@C to obtain Cu2S/C@NiMnCe-LDH rods. At a current density of 2 mA cm-2, Cu2S/C@NiMnCe-LDH/CF exhibits an area capacitance of 5176.4 mF cm-2. The mass capacitance and the energy density of the Cu2S/C@NiMnCe-LDH/CF//AC asymmetric supercapacitor (ASC) reach 150.82F g-1 at a sweep rate of 0.8 A/g and 53.62 Wh kg-1 at a power density of 639.99 W kg-1, respectively. Meanwhile, after 8000 electrochemical cycles, the specific capacitance of Cu2S/C@NiMnCe-LDH/CF//AC still has a retention rate of 86.32 %, which proves its excellent cycling stability. These results demonstrate a new strategy for the preparation of novel core-shell structured Cu2S/C@NiMnCe-LDH/CF nanocomposite material for electrode materials of energy storage devices with superb performance.

Enhanced Replenishment of Active Lattice Oxygen Using Chiral Copper Oxide

Effective catalytic performance of the transition metal oxide is attributed to high specific surface areas, abundant surface oxygen atoms, and balanced valence ratios. Although the chirality of the transition metal has attracted attention, most studies have focused on optical application. A few chiral transition metal oxides were used as electrocatalysts and photocatalysts. The influence of the chiral catalysts on the thermal catalysis process has been less explored. In this study, Mn-loaded chiral (M/l-CuO and M/d-CuO) and achiral CuO (M/a-CuO) were synthesized and compared in the catalytic oxidization of toluene. Spectrally analyzed Mn was well-dispersed on both chiral and achiral CuO. l-CuO and d-CuO showed nanoflower-like chirality. The angles between each (001) plane of CuO were the source of chirality. The toluene turnover frequency (TOF) of the samples was in the order of Mn/d-CuO (5.6 × 10-5 s-1) > Mn/l-CuO (4.4 × 10-5 s-1) > Mn/a-CuO (3.2 × 10-5 s-1) at 240 °C, consistent with the order of the oxygen replenishment rate. The as-prepared catalysts had similar ratios of lattice oxygen/surface adsorbed oxygen, Mn3+/Mn4+, and Cu+/Cu2+. A higher TOF was attributed to chirality, which increased the lattice oxygen replenishment speed from the gaseous phase to the solid surface. Our study indicates gas-solid catalysis from a structure-activity viewpoint.

Rational Construction of a Triple-Phase Reaction Zone Using CuO-Based Heterostructure Nanoarrays for Enhanced Water Oxidation Reaction

The development of high-efficiency oxygen evolution reaction (OER) electrocatalysts for the production and conversion of clean energy is paramount yet also full of challenges. Herein, we proposed a simple and universal method to precisely fabricate the hierarchically structured CuO/TMOs loaded on Cu foil (CuO/TMOs/CF) (TMO represents Mn3O4, NiO, CoO, and CuO) nanorod-array electrodes as a highly active and stable OER electrocatalyst, employing Cu(OH)2/CF as a self-sacrificing template by the subsequent H2O2-induced chemical deposition (HiCD) and pyrolysis process. Taking CuO/Mn3O4/CF as an example, we systematically investigated its structure-performance relationship via experimental and theoretical explorations. The enhanced OER activity can be ascribed to the rational design of the nanoarray with multiple synergistic effects of abundant active sites, excellent electronic conductivity of the metallic Cu foil substrate, strong interface charge transfer, and quasi-superhydrophilic/superaerophobic property. Consequently, the optimal CuO/Mn3O4/CF presents an overpotential of 293 mV to achieve a current density of 20 mA cm-2 in 1.0 M KOH media, comparable to that of commercial RuO2 (282 mV), delivering excellent durability by the electrolysis of water at a potential of around 1.60 V [vs reversible hydrogen electrode (RHE)] without evident degeneration. This work might offer a feasible scheme for developing a hybrid nanoarray OER electrocatalyst via regulating electron transportation and mass transfer.

Enhancing electro-reduction of nitrite to ammonia by loading Co3O4 on CuO to construct elecrocatalytic dual-sites

Improving the performance of CuO in electrocatalytic nitrite reduction to ammonia (NIRA) is the priority for designing efficient NIRA electrocatalysts. The electrocatalytic activity of CuO was enhanced by growing Co₃O₄ nanospheres on it. By comparing Co₃O₄@CuO with the mechanically mixed CuO and Co₃O₄ on a rotating ring-disk electrode, we discovered that the enhancement was attributed to a dual-site catalytic pathway.

In Situ Generation of Vertically Crossed P-Cu3Se2 Ultrathin Nanosheets Derived from Cu2S Nanorod Arrays for High-Performance Supercapacitors

Transition-metal selenides (TMSs) have great potential in the synthesis of supercapacitor electrode materials due to their rich content and high specific capacity. However, the aggregation phenomenon of TMS materials in the process of charging and discharging will cause capacity attenuation, which seriously affects the service life and practical applications. Therefore, it is of great practical significance to design simple and efficient synthesis strategies to overcome these shortcomings. Hence, P-doped Cu₃Se₂ nanosheets are loaded on vertically aligned Cu₂S nanorod arrays to synthesize CF/Cu₂S@Cu₃Se₂/P nanocomposites with a unique core-shell heterostructure. Notably, the Cu₂S precursors can be rapidly converted into Cu₃Se₂ nanorod arrays in situ in just 30 min at room temperature. The unique core-shell heterostructure effectively avoids the aggregation phenomenon, and the doped P elements further enhance the electrochemical properties of the electrode materials. Therefore, the as-prepared CF/Cu₂S@Cu₃Se₂/P electrode exhibits a high areal capacitance of 5054 mF cm^-2 (1099 C g^-1) at 3 mA cm^-2 and still retains 90.2% capacitance after 10 000 galvanostatic charge-discharge (GCD) cycles. The asymmetric supercapacitor (ASC) device assembled from synthetic CF/Cu₂S@Cu₃Se₂/P and activated carbon (AC) possesses an energy density of 41.1 Wh kg^-1 at a power density of 480.4 W kg^-1. This work shows that the designed CF/Cu₂S@Cu₃Se₂/P electrode has broad application prospects in the field of electrochemical energy storage.

Ternary NiCeCo-Layered Double Hydroxides Grown on CuBr2@ZIF-67 Nanowire Arrays for High-Performance Supercapacitors

Ternary layered double-hydroxide-based active compounds are regarded as ideal electrode materials for supercapacitors because of their unique structural characteristics and excellent electrochemical properties. Herein, an NiCeCo-layered double hydroxide with a core-shell structure grown on copper bromide nanowire arrays (CuBr₂@NCC-LDH/CF) has been synthesized through a hydrothermal strategy and calcination process and utilized to fabricate a binder-free electrode. Due to the unique top-tangled structure and the complex assembly of different active components, the prepared hierarchical CuBr₂@NCC-LDH/CF binder-free electrode exhibits an outstanding electrochemical performance, including a remarkable areal capacitance of 5460 mF cm^-2 at 2 mA cm^-2 and a capacitance retention of 88% at 50 mA cm^-2 as well as a low internal resistance of 0.163 Ω. Moreover, an all-solid-state asymmetric supercapacitor (ASC) installed with CuBr₂@NCC-LDH/CF and activated carbon electrodes shows a high energy density of 118 Wh kg^-1 at a power density of 1013 W kg^-1. Three assembled ASCs connected in series can operate a multifunctional display for over three and a half hours. Therefore, this innovative work provides new inspiration for the preparation of electrode materials for supercapacitors.

Origami and layered-shaped ZnNiFe-LDH synthesized on Cu(OH)2 nanorods array to enhance the energy storage capability

The combination of layered nanorod arrays with unique core-shell structure and transition metal layered double hydroxide (LDH) is considered as a feasible solution to improve the electrochemical performances of capacitor electrode. In this study, layered ZnNiFe-LDH@Cu(OH)₂/CF core-shell nanorod arrays, which consist of ultrathin ZnNiFe-LDHs nanosheet shells and ordered Cu(OH)₂ nanorod inner cores, are successfully designed and fabricated by a typical hydrothermal way and a simple in situ oxidation reaction. The electrode prepared using ZnNiFe-LDH@Cu(OH)₂/CF nanomaterial reveals an remarkable area capacitance of 6100 mF cm^-2 at 3 mA cm^-2 current density, which is excellently superior than those of ZnFe-LDH@Cu(OH)₂/CF, NiFe-LDH@Cu(OH)₂/CF, Cu(OH)₂/CF and CF. Additionally, the capacitance retention remains as high as 83.4% after 5000 cycles and a very small Rs (0.567 Ω) can be observed. In addition, an asymmetric supercapacitor device is successfully fabricated employing ZnNiFe-LDH@Cu(OH)₂/CF. Meanwhile, the ZnNiFe-LDH@Cu(OH)₂/CF//AC device can achieve an energy density of 44 Wh kg^-1 and a corresponding power density of 720 W kg^-1 and possess the capability to light up a multi-function monitor for 33 min just using two ASC equipments connected in series. Therefore, the prepared ZnNiFe-LDH@Cu(OH)₂/CF composite materials with unique structure has great application potential in energy storage devices.

Enhanced energy storage of aqueous zinc-carbon hybrid supercapacitors via employing alkaline medium and B, N dual doped carbon cathode

Zinc-based energy storage systems (zinc-air, zinc-nickel and zinc-ion batteries and zinc-ion hybrid supercapacitors (ZHSs) are considered as promising power sources for wide applications from personal electronic devices to electric vehicles. However, these systems, especially the Zn-based hybrid supercapacitors, display unsatisfying power density and energy density, which should be enhanced for their large-scale applications. In this work, aqueous alkaline zinc-carbon hybrid supercapacitors (A-ZCHS) were designed, consisting of B, N dual doped carbon cathode, Zn anode and KOH electrolyte. The B, N dual doped carbon was prepared via thermal treatment of metal-organic frameworks and boric acid, which exhibits abundant hierarchical pore structure (micropore, mesopore and macropore) and suitable defect construction, promoting ion diffusion/charge transfer and providing more rapid surface pseudocapacitance reaction. More obviously, when the optimized B, N dual doped carbon was used as cathode in A-ZCHS and ZHS, more capacitive charge storage and rapider electrochemical kinetics can be observed in A-ZCHS than in ZHS. Therefore, the optimized A-ZCHS displays a high energy density of 115.7 Wh kg^-1 at the power density of 711.6 W kg^-1 with excellent stability, which is much better than most of ZHSs reported previously. The A-ZCHS should be a promising candidate for energy storage applications.

Direct Utilization of Photoinduced Charge Carriers to Promote Electrochemical Energy Storage

Electrochemical energy storage has been regarded as one of the most promising strategies for next-generation energy consumption. To meet the increasing demands of urban electric vehicles, development of green and efficient charging technologies by exploitation of solar energy should be considered for outdoor charging in the future. Herein, a light-sensitive material (copper foam-supported copper oxide/nickel copper oxides nanosheets arrays, namely CF@CuO_x @NiCuO_x NAs) with hierarchical nanostructures to promote electrochemical charge storage is specifically fabricated. The as-fabricated NAs have demonstrated a high areal specific capacity of 1.452 C cm^-2 under light irradiation with a light power of 1.76 W, which is 44.8% higher than the capacity obtained without light. Such areal specific capacity (1.452 C cm^-2 ) is much higher than that of the conventional supercapacitor structure using a similar active redox component reported recently (NiO nanosheets array@Co₃ O₄ -NiO FTNs: maximum areal capacity of 623.5 mF cm^-2 at 2 mA cm^-2 ). This photo-enhancement for charge storage can be attributed to the combination of photo-sensitive Cu₂ O and pseudo-active NiO components. Hence, this work may provide new possibilities for direct utilization of sustainable solar energy to realize enhanced capability for energy storage devices.

Calcination Strategy for Scalable Synthesis of Pithecellobium-Type Hierarchical Dual-Phase Nanostructured Cu x O to Columnar Self-Assembled CuO and Its Electrochemical Performances

The search for low-cost environmentally benign promising electrode materials for high-performance electrochemical application is an urgent need for an applaudable solution for the energy crisis. For this, the present attempt has been made to develop a scalable synthetic strategy for the preparation of pure and dual-phase copper oxide self-hybrid/self-assembled materials from a copper oxalate precursor using the calcination route. The obtained samples were characterized by means of various physicochemical analytical techniques. Notably, we found that the BET surface area and pore volume of copper oxides measured by N2 adsorption-desorption decrease with the elevation of calcination temperature. From the XRD analysis, we observed the formation of a Cu2O cubic phase at low temperatures and a CuO monoclinic phase at high temperatures (i.e., 450 and 550 °C). FTIR and RAMAN spectroscopy were employed for bonding and vibrational structure analysis. The self-assembled dual-phase copper oxide particle as a pithecellobium-type hierarchical structure was observed through SEM of the sample prepared at 350 °C. The surface morphological structure for the samples obtained at 450 and 550 °C was a bundle-like structure developed though columnar self-assembling of the particles. All the above techniques confirmed the successful formation of Cu2O/CuO nanoparticles. Afterward, the electrochemical properties of the as-synthesized copper oxides reinforced by introducing carbon black (10% wt) were explored via cyclic voltammetry, electrochemical impedance spectroscopy, and galvanometric charge-discharge analysis. The Cu2O system exhibits the maximum specific capacitance performance value of 1355 F/g, whereas in the CuO system (at 450 and 550 °C), it possesses values of 903 and 724 F/g at a scan rate of 2 mV/s. This study reveals that the electrochemical properties of Cu2O are better than those of the CuO nanoparticles, which could be ascribed to the high surface area and morphology. The present assessment of the electrochemical properties of the developed material could pave the way to a low-cost electrode material for developing other high-performance hybrid electrodes for supercapacitor or battery applications.

Construction of hierarchical layered hydroxide grown in situ on carbon tubes derived from a metal-organic framework for asymmetric supercapacitors

Electrode materials are very important for the performance of supercapacitors (SCs). Therefore, preparation of hybrid electrode materials is an effective way to develop high-performance SCs. We firstly design and prepare metal organic framework (MOF) derived carbon nanotubes as the core skeleton to support the shell of a nickel gallium layered hydroxide nanosheet (NiGa-LDH). MOF derived carbon nanomaterials have high conductivity and a large specific surface area, which can promote electron transfer and improve the agglomeration of LDH. The deposited LDH can provide high specific capacitance and the layered structure can further enhance the reaction site. The NiGa-LDH@CNT-500@CC has an excellent specific capacitance of 2580 F g-1 at 1 A g-1 and a high capacitance retention rate of 83.3% at 5 A g-1 due to the synergistic effect of two materials. The assembled NiGa-LDH@CNT-500@CC//carbon NS asymmetric supercapacitor (ASC) has an operating voltage of 1.6 V and a high energy density of 52 W h kg-1 at a power density of 952 W kg-1. Therefore, the core-shell structure composed of LDH and carbon nanomaterials provides an effective way for the design of high-performance electrodes.

Encapsulation of Co3 O4 Nanocone Arrays via Ultrathin NiO for Superior Performance Asymmetric Supercapacitors

Designing of multicomponent transition metal oxide system through the employment of advanced atomic layer deposition (ALD) technique over nanostructures obtained from wet chemical process is a novel approach to construct rational supercapacitor electrodes. Following the strategy, core-shell type NiO/Co₃ O₄ nanocone array structures are architectured over Ni-foam (NF) substrate. The high-aspect-ratio Co₃ O₄ nanocones are hydrothermally grown over NF following the precision controlled deposition of shell NiO considering Co₃ O₄ nanocone as host. NiO thickness of 5 nm exhibits the highest specific capacity of 1242 C g^-1 (2760 F g^-1 ) at current density 2 A g^-1 , which is greater than pristine Co₃ O₄ @NF (1045.8 C g^-1 or 2324 F g^-1 ). The rate capability with 5 nm NiO/Co₃ O₄ @NF nanocone structures is about 77% whereas Co₃ O₄ @NF retains 46 % of capability at 10 A g^-1 . The ultrathin ALD 5 nm NiO accelerates both rate capability and 95.5% cyclic stability after 12 000 charge-discharge cycles. An asymmetric device fabricated between 5 nm NiO/Co₃ O₄ @NF (positive) || activated carbon (negative) achieves an energy density of 81.45 Wh kg^-1 (4268 W kg^-1 ) with good cycling device stability. Additionally, LEDs can be energized by two ASC device in series. This work opens the path in both advanced electrode material and surface modification of earth-abundant systems for efficient and real-time supercapacitor applications.

Electrode Materials for Supercapacitors: A Review of Recent Advances

The advanced electrochemical properties, such as high energy density, fast charge–discharge rates, excellent cyclic stability, and specific capacitance, make supercapacitor a fascinating electronic device. During recent decades, a significant amount of research has been dedicated to enhancing the electrochemical performance of the supercapacitors through the development of novel electrode materials. In addition to highlighting the charge storage mechanism of the three main categories of supercapacitors, including the electric double-layer capacitors (EDLCs), pseudocapacitors, and the hybrid supercapacitors, this review describes the insights of the recent electrode materials (including, carbon-based materials, metal oxide/hydroxide-based materials, and conducting polymer-based materials, 2D materials). The nanocomposites offer larger SSA, shorter ion/electron diffusion paths, thus improving the specific capacitance of supercapacitors (SCs). Besides, the incorporation of the redox-active small molecules and bio-derived functional groups displayed a significant effect on the electrochemical properties of electrode materials. These advanced properties provide a vast range of potential for the electrode materials to be utilized in different applications such as in wearable/portable/electronic devices such as all-solid-state supercapacitors, transparent/flexible supercapacitors, and asymmetric hybrid supercapacitors.