Conductive Nickel Foam Research Articles

Engineering intervention to disrupt the evolution of ZIF-67: Ultra-fast synthesis of arrayed Co(OH)2@ZIF-L in dozens of seconds for high-energy charge storage

Designing rational heterostructures of high-performance electroactive materials on conductive substrates with hierarchical structures is critical for advancing electrochemical energy storage technologies. In this study, a unique spatial structure is fabricated by vertically aligning two-dimensional (2D) structures of Co-ZIF-L on conductive nickel foam (NF) substrate through interruption of ZIF-67 formation. This is followed by an innovative electrochemical synthesis method that disrupts unstable surface coordination bonds in Co-ZIF-L, enabling the in-situ generation of Co(OH)2. The resulting Co(OH)2@ZIF-L/NF binder-free electrodes feature a hierarchical spatial structure and are synthesized in approximately 30 s. These electrodes showcase exceptional area capacity of 3.1 C cm−2 at 1 mA cm−2, attributed to their high specific surface area and layered architecture that promotes electrolyte penetration. Density Functional Theory (DFT) calculations reveal that the Co(OH)2@ZIF-L nanostructures have superior electrical conductivity compared to the individual components. Furthermore, a hybrid supercapacitor (HSC) based on Co(OH)2@ZIF-L/NF//AC exhibits an impressive energy density of 42 Wh kg−1 at a power density of 184.7 W kg−1. This research provides new insights into the efficient synthesis of high-performance electroactive materials with unique spatial structures and expands the potential applications of ZIF materials.

Impedimetric identification of heteroMOFs modified porous nickel foam self-supports as robust electrodes for CA 19-9 pancreatic tumor marker in human serum

An impedance-based electrochemical immunosensor for direct and binder-free target recognition of carbohydrate antigen (CA 19-9) tumor biomarker for the early diagnosis of pancreatic cancer was reported. This study uses an in situ solvothermal process to develop a simple method for the one-pot construction of Ni-Fe heteroMOFs (HFNMOFs,) self-supported on conductive nickel foam (NicFm). Utilizing HFNMOFs@NicFm developed in this study, the electrochemical performance of the biosensor was studied for the first time. The as-prepared mixed MOFs decorated NicFm electrodes displayed potential electrochemical outputs. They demonstrated the potential for developing binder-free non-enzymatic immunosensors with wide linear limits, high selectivity, stability, and excellent sensitivity. The bifunctional MOFs exhibit improved electrochemical conductivity owing to the highly exposed metal sites and hierarchical porosity. The changes in the charge transfer resistance present a linear response against increasing target concentrations. The immunosensor developed in this study exhibited its detection limit of 2.56 U/mL. Further, the bioelectrodes produced were validated against real human spiked serum with good results of percentage recovery, indicating the immunosensor is well-suitable to be tested in real-time analysis.

Development of three-dimensional iron-doped cobalt phosphides nanorod arrays coupled on nickel substrate for effective hydrogen and oxygen production

To reach practical generation of hydrogen energy from water, it is necessary to synthesize bifunctional effective and durable electrocatalyst towards hydrogen evolution and oxygen evolution reaction (HER and OER). However, the slow kinetics of HER and OER at the cathode and anode is the main bottleneck. Herein, a novel fabrication nanostructure of iron-doped cobalt phosphides nanorod arrays on a conducting nickel foam substrate (Fe-CoxPy NR/NF) is developed with uniform spreading of dopant, high catalytic activity area, rapid efficiency of interfacial charge transfer, and long-time operation by using a facile hydrothermal process and phosphidization. The results displayed that Fe-CoxPy NR/NF exhibited an effective overpotential of 98 mV towards HER and 290 mV towards OER at 10 mA cm−2, which are much lower than those individual CoxPy NR and Fe-CoOH NR materials. In addition, the Fe-CoxPy NR/NF show significant stability in 1.0 M KOH, compared to commercial materials.

Synergistic effect of co-sputtered tungsten-titanium nitride as electrode material for efficient hybrid supercapacitors

The dawn of bimetallic transition metal nitrides has attracted considerable interest as battery grade electrode material for potential energy storage applications. In addition, it is essential to investigate binder-free processes to improve the performance of the fabricated electrodes. In this study, binder-free tungsten‑titanium nitrides (W-TiN) are deposited through RF/DC magnetron co-sputtering onto the conducting nickel foam (NF). SEM, EDX and X-ray diffraction are exploited to investigate surface morphology, elemental composition, and structural properties of sputtered materials. The W-TiN electrodes are characterized through electrochemical investigation in half-cell configuration. The tested W-TiN electrode is further utilized with activated carbon (AC) electrode to develop hybrid supercapacitor device W-TiN//AC. The hybrid device revealed a maximum energy density (Es) of 88.8 Wh/kg and power density (Ps) 1700 W /kg. To further understand the mechanism of hybrid devices, the capacitive and diffusive contributions are computed using linear and quadradic models. This study provides a new direction to integrate co-sputtered binder-free electrode materials and devices for large scale production of advanced hybrid energy storage devices.

Seamless integration of a nickel-based metal-organic framework with three-dimensional substrates for nonenzymatic glucose sensing.

The effective integration of nanomaterials with underlying current collectors is a key factor affecting the performance of nonenzymatic glucose sensors, where an inappropriate integration structure often leads to poor electron transport and instability. In this work, a seamless integrated electrode was constructed by the in situ immobilizing of a nickel-based metal-organic framework (Ni-MOF) on a three-dimensional (3D) conductive nickel foam (NF) for highly sensitive and durable glucose sensing. Facilitated by a rapid microwave-assisted reaction, a robust interfacial interaction between the Ni-MOF and the substrate was established through in situ conversion from nickel oxide (NiO). The fabricated Ni-MOF/NF electrode exhibits an excellent limit of detection (LOD) of 2.65 μM and an impressive sensitivity (14.31 mA cm-2 mM-1) within the linear range (4-576 μM), which is significantly boosted compared with that of an electrode prepared by a typical drop-casting method (3.56 mA cm-2 mM-1 in 4-1836 μM). Characterization and electrochemical tests reveal that this integrated structure on the one hand contributes to fast electron transport and thus has enhanced sensitivity and on the other hand leads to exceptional durability with its structural integrity maintained under bending, shaking, and ultrasonication. Moreover, this seamless integration method was also employed to immobilize the Ni-MOF converted from the pre-chemically deposited NiO layer on another type of substrate, 3D carbon paper (CP), demonstrating the versatility of this facile strategy in creating diverse electrochemical electrodes for applications beyond glucose sensing.

Synergistic interfacial electronic modulation of topotactically developed bimetallic CoNiP on NiS nanorods for enhanced alkaline hydrogen evolution reaction.

Designing hybrid transition metal phosphosulfide electrocatalysts is critical for the hydrogen evolution reaction (HER). We propose a novel approach by designing a hierarchical structure of cobalt phosphide (CoP) and nickel phosphide (Ni8P3) nanoparticles topotactically developed on nickel sulfide (Ni3S2) nanorods (CoNiP/NiS) via a sulfuration-phosphorization strategy using conductive 3D nickel foam. Hierarchical heterostructured nanorods were achieved without the need for template removal steps or the assistance of surfactants. This not only simplifies the process but also improves the exposure of active sites for catalytic purposes. Furthermore, the theoretical calculation results revealed that the high H* adsorption-free energy for CoP and Ni8P3 phases significantly decreases upon coupling with Ni3S2, which indicates that the interfacial electronic interaction synergistically modulates both CoP and Ni8P3 (CoNiP) at the coupled interfaces and facilitates the adsorption and desorption of H* intermediates during the HER process. The resulting electrode exhibits excellent performance in the HER catalytic process and shows great performance for further exploration in the urea oxidation reaction (UOR). Our work provides a stepping stone toward rational topotactic transformation of active materials on porous substrates, using electronic structure regulation and heterointerfaces to produce promising electrocatalysts for sustainable, large-scale hydrogen production from water electrolysis.

Iron and vanadium co-doped Ni3S2 flower like nanosheets as an efficient electrocatalysts for water splitting

For the production of sustainable hydrogen energy from water electrolysis, it is now essential to create an efficient bifunctional electrocatalysts for OER and HER (oxygen and hydrogen evolution reaction). We have synthesized a bi-metallic heterogeneous electrocatalyst of iron and vanadium codoped nickel sulphide (FeV-Ni3S2) flower like nanosheets self-supported on conductive nickel foam (NF) substrate by a typical hydrothermal method. Herein, our investigation is focused on achieving an efficient electrocatalytic performance and long-term stability (> 48 h) in an alkaline environment (1 M KOH). The results of FeV-Ni3S2/NF exhibits an outstanding electrochemical performance with lower overpotentials of 149 mV for HER and 183 mV for OER at 10 mA cm−2, and a lower cell voltage of 1.56 V, respectively. The lattice distortion in Ni3S2 caused by FeV-doping, and the enrichment of sulphur active edge sites contributes to the improved electrochemical performance of FeV-Ni3S2/NF. Moreover, the interconnected flower like nanosheets increasese the conductivity, density of active sites and electrochemical surface area to facilitate the mass transport of reactants, benefiting stable water electrolysis for efficient hydrogen production. This work will provide novel insights into the design of bi-metal-doped materials for energy conversion and storage applications.

MoS2 modified NiFe LDH hierarchical structure as efficient photoanode towards photoelectrochemical water splitting

Designing effective photo electrode for photo-electrochemical (PEC) water splitting is highly demanded yet challengeable because of the limited sunlight utilization and retarded redox reaction kinetics. This work introduces a feasible one-pot hydrothermal strategy of fabricating MoS2/NiFe LDH p-n heterojunctions on conductive porous nickel foam as an efficient photoanode for PEC water splitting. A great enhancement for PEC water oxidation is achieved because of the improved sunlight absorption and the increased photo-excited charge separation. The optimal 10% MoS2/Ni0.9Fe0.1 LDH/nickel foam photoanode demonstrates 3.8 times enhanced PEC activity than the Ni0.9Fe0.1 LDH/NF counterpart and a low Tafel plot of 54 mV dec−1. The bandgap modulation and the Z-scheme charge transfer dynamics due to the formation of MoS2/NiFe LDH p-n heterostructure, along with the high conductivity of porous nickel foam account for the increased photo-current conversion efficiency and the boosted charge transfer.

Core–shell heterostructure engineering of CoP nanowires coupled NiFe LDH nanosheets for highly efficient water/seawater oxidation

Searching for efficient nonprecious metal-based catalysts toward oxygen evolution reaction (OER) are of significance for seawater electrolysis. Herein, a core–shell-structured hybrid of cobalt phosphide nanowires@NiFe layered double hydroxide nanosheets grown on conductive nickel foam (CoP@NiFe LDH/NF) is prepared by a feasible approach at low temperature. The charming structure can provide numerous phosphide/hydroxide heterogenous interfaces, expose abundant active sites, and boost electron/mass transfer, synergistically enhancing catalytic OER activity. When employed as an electrocatalyst toward the OER, the resultant CoP@NiFe LDH/NF only requires a small overpotential of 287 mV to provide 300 mA/cm2 current density as well as long-time durability in 1.0 mol/L KOH seawater. The regulation of electronic states and surface reconstruction synergistically contribute to highly efficient seawater oxidation. This work provides an opportunity to construct efficient and inexpensive electrocatalysts for hydrogen production.

Construction of Binder-Free, Self-Supported, Hetero-Core-Shell Honeycomb Structured CuCo2 O4 @Ni0.5 Co0.5 (OH)2 with Abundant Mesopores and High Conductivity for High-Performance Energy Storage.

Clever and rational design of structural hierarchy, along with precise component adjustment, holds profound significance for the construction of high-performance supercapacitor electrode materials. In this study, a binder-free self-supported CCO@N0.5 C0.5 OH/NF cathode material is constructed with hierarchical hetero-core-shell honeycomb nanostructure by first growing CuCo2 O4 (CCO) nanopin arrays uniformly on highly conductive nickel foam (NF) substrate, and then anchoring Ni0.5 Co0.5 (OH)2 (N0.5 C0.5 OH) bimetallic hydroxide nanosheet arrays on the CCO nanopin arrays by adjusting the molar ratio of Ni(OH)2 and Co(OH)2 . The constructed CCO@N0.5 C0.5 OH/NF electrode material showcases a wealth of multivalent metal ions and mesopores, along with good electrical conductivity, excellent electrochemical reaction rates, and robust long-term performance (capacitance retention rate of 87.2%). The CCO@N0.5 C0.5 OH/NF electrode, benefiting from the hierarchical structure of the material and the exceptional synergy between multiple components, demonstrates an excellent specific capacitance (2553.6 F g-1 at 1 A g-1 ). Furthermore, the assembled asymmetric CCO@N0.5 C0.5 OH/NF//AC/NF supercapacitor demonstrates a high energy density (70.1Wh kg-1 at 850W kg-1 ), and maintains robust capacitance cycling stability performance (83.7%) after undergoing 10000 successive charges and discharges. It is noteworthy that the assembled supercapacitor exhibits an operating voltage (1.7V) that is well above the theoretical value (1.5V).

Conductive N, S doped Copolymers as Stable Metal-Free Electrocatalysts for Water Splitting.

Noble metals (Pt) and metal oxides (IrC and RuO2) are heavily utilized as benchmark electrocatalysts for alkaline water splitting; however, these materials possess several drawbacks including high cost, poor selectivity and stability, and high environmental impact. To address these issues, we synthesized a novel metal-free conducting polypyrrole-polythiophene (Ppy-Ptp) copolymer and a separate Ppy electrode material for water-splitting applications. The Ppy-Ptp and Ppy electrocatalysts exhibited remarkable activity in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The optimal Ppy-Ptp (1:3) formulation, when deposited on a conductive nickel foam (NF) substrate, exhibited an exceptional OER performance with a low overpotential of approximately 250 mV at 20 mAcm-2, thereby outperforming the benchmark IrC/NF electrocatalyst (290 mV, 20 mAcm-2). Additionally, a similarly prepared Ppy/NF electrocatalyst exhibited an extraordinary HER performance with an overpotential of approximately 72 mV at 10 mA cm-2. Furthermore, an alkaline anion-exchange membrane (AEM) electrolyzer incorporating Ppy-Ptp (1:3) and Ppy as the anode and cathode materials, respectively, displayed operating potentials of 1.55, 1.70, and 1.78 V at 10, 50, and 100 mA cm-2, which are lower than those observed in previously reported electrolyzers. This electrolyzer also exhibited considerable operational endurance over 50 h at 50 mA cm-2, over which a negligible decay of 0.02 V was observed. The novel polymer-based metal-free catalysts presented herein therefore exhibit considerable potential as alternative electrocatalytic materials for sustainable industrial-scale H2 synthesis.

Synergistic coupling of MnS/Ni3S2 and Co(OH)2 nanosheets as binder-free electrode materials for asymmetric supercapacitors with enhanced performance

The fabrication of electrode materials with a high specific capacitance is essential for the development of enhanced performance supercapacitors. A novel binder-free electrode material, composed of MnS/Ni3S2 and Co(OH)2, was synthesized on nickel foam by hydrothermal, sulfuration, and electrodeposition techniques. The MnS/Ni3S2 exhibited a unique flower-like structure, resulting in a high specific capacitance of 1780 F g−1 at 1 A/g. By optimizing the synthesis conditions through several characterization and electrochemical tests, the MnS/Ni3S2@Co(OH)2 composite was obtained, which displayed an ultrahigh specific capacitance of 2495 F g−1 at 1 A/g and a capacitance retention rate of 86.1% after 5000 cycles at 10 A/g in three-electrode system. The synergistic coupling of MnS/Ni3S2 and Co(OH)2, along with the conductive nickel foam substrate, donated towards the excellent electrochemical performance. Furthermore, the MnS/Ni3S2@Co(OH)2//AC asymmetric supercapacitor (ASC) device was constructed with MnS/Ni3S2@Co(OH)2 as positive electrode, activated carbon (AC) as negative electrode and 1 M KOH solution as electrolyte, demonstrated a high energy density of 68.6 Wh kg−1 at 750 W kg−1 and excellent cycle stability with 91.2% capacitance retention after 10,000 cycles at 15 A/g. The outstanding electrochemical properties observed in both the pre-electrodeposition and post-electrodeposition samples indicate the effectiveness of reasonable design and construction of composite as a pathway for producing electrode materials with exceptional performance.

Constructing metal organic framework derived manganese cobalt layered double hydroxide nanosheets on Ni foam as cost-effective binder-free electrodes of high-performance supercapacitors

A vital aspect of energy storage devices is the development of novel materials with excellent electrical conductivity and rational structures. In combination with alkaline electrolytes, the manganese-cobalt layered double hydroxide (MnCo-LDH) cathode material has long been recognized as a highly desirable cathode material. Nevertheless, the synthesis of MnCo-LDH is time-consuming and required high temperatures. Therefore, it is important to find simple routes for the synthesis of MnCo-LDH. Herein, we propose a synthesis of metal organic framework (MOF)-derived MnCo-LDH nanosheets on conductive nickel foam (NF) for the supercapacitor (SC) application. The CoMOF decorated NF was fabricated by simple precipitation method, and then it was converted to MnCo-LDH by etching process at 80 °C for 5 min (MnCo-LDH/80 °C). The MOF-derived MnCo-LDH/80 °C electrode provides large accessible regions for electrolytes, low charge transfer resistance, and rich electroactive sites. Therefore, the MnCo-LDH/80 °C electrode demonstrates preferable energy storage property with a high areal capacitance of 2.62 F/cm2 at 20 mV/s. In this study, an asymmetric supercapacitor (ASC) is constructed using MnCo-LDH/80 °C and activated carbon (AC) on NF as the positive and negative electrodes, respectively. The optimized MnCo-LDH//AC device provides the maximum energy of 0.116 mWh/cm2 at the maximum power density of 2.49 mW/cm2. Added to that, the ASC has excellent cyclic stability with 78% as the capacitance retention and Coulombic efficiency of 94.3% after 5000 charge-discharge cycles.

Simultaneous Solar-Thermal Desalination and Catalytic Degradation of Wastewater Containing Both Salt Ions and Organic Contaminants.

Although solar steam generation is promising in generating clean water by desalinating seawater, it is powerless to totally degrade organic contaminants in the seawater. Herein, solar steam generation and catalytic degradation are integrated to generate clean water by simultaneous solar-driven desalination and catalytic degradation of wastewater containing both salt ions and organic contaminants. Stepwise decoration of three-dimensional nickel foam with polypyrrole, reduced graphene oxide (RGO), and cobalt phosphate is realized to obtain polypyrrole/RGO/cobalt phosphate/nickel foam (PGCN) hybrids for solar-driven desalination and catalytic degradation of wastewater containing antibiotics and salt ions. The oxygen-containing groups of the RGO integrated with the porous nickel foam make the porous PGCN hybrid hydrophilic and ensure the upward transport of water to the evaporation surface, and the oxygen vacancies of the cobalt phosphate allow the PGCN to generate abundant highly active singlet oxygen that could still exhibit excellent catalytic degradation performances in the high salinity and highly alkaline environment of seawater. In addition to the high solar light absorbance and satisfactory solar-thermal conversion efficiency of polypyrrole and RGO, the thermally conductive nickel foam skeleton can effectively transfer the heat generated by the solar-thermal energy conversion to the adjacent cobalt phosphate catalyst and nearby wastewater, achieving a solar-thermal-promoted catalytic degradation of organic contaminants. Therefore, a high pure water evaporation rate of 2.08 kg m-2 h-1 under 1 sun irradiation and 100% catalytic degradation of Norfloxacin and dyes are achieved. The PGCN hybrid is highly efficient in purifying seawater containing 10 ppm Norfloxacin and simultaneously achieves a high purification efficiency of 100 kg m-2 h-1.

Highly efficient atomic hydrogen-mediated electrochemical hydrodehalogenation of trichloroacetic acid on 3D hierarchical multi-transition metal selenides

Halogenated organic compounds as highly focused emerging contaminants pose a long-lasting threat to human health and the aquatic environment due to their high toxicities and strong anti-biodegradation characteristics. Electrochemical hydrodehalogenation (ECHD) is a promising technology with a low-carbon footprint to remove halogenated organic compounds while suffering from a lack of efficient and robust earth-abundant electrocatalysts. Herein, by integrating two kinds of transition metal dichalcogenides (i.e., MoSe2 nanosheet and Ni3Se2 nanowire) into a conductive 3D porous network nickel foam, we obtained a hierarchical architecture (MoSe2/Ni3Se2@NF) that promises high surface area, fast charge transfer and efficient mass transfer. The interface-confined epitaxial growth of Ni3Se2 nanowires on nickel foam provides abundant sites for the vertical growth of MoSe2 nanosheets, which endows MoSe2 with maximal accessible active edge sites to participate in the ECHD process. Benefiting from such a hierarchical 3D porous configuration, trichloroacetic acid (5 mg/L) was removed over 95% by MoSe2/Ni3Se2@NF at − 1.2 V vs. SCE after 1 h, which dramatically outperformed that for NF (20%) and Ni3Se2@NF (53.2%). The major contributor to such boosted performance is the adsorbed atomic hydrogen (*H) generated during water splitting via suppressing hydrogen-hydrogen dimerization, as evidenced by radical quenching experiments and electron paramagnetic resonance spectroscopy. This study offers appealing opportunities for tailoring the catalytic performance of noble-metal-free heterogeneous catalysts for various applications that require noble-metal catalysts.

Fe3+ induced etching of NiCo-MOF derived transformations into layered ternary hydroxides as efficient oxygen evolution catalyst

Hydrogen energy is the only new energy that meets the requirements of resources, environment and sustainable development due to its advantages such as rich resources, diverse sources, storable, renewable, high calorific value, clean and pollution-free. Electrochemical water splitting technology can achieve large-scale hydrogen production commercially, but the slow kinetics of OER process seriously hinders the development of electrochemical water splitting technology, therefore, high-efficiency and low-cost OER electrocatalyst is urgently needed. Here, we synthesized a layered ternary hydroxide NiCoFe-LTH@NiCo-MOF/NF-30 electrocatalyst with NiCo-MOF as the sacrificial template on conductive substrate nickel foam by a two-step solvothermal method, which requires only low overpotentials of 207 mV and 283 mV to achieve current densities of 10 mA cm−2 and 100 mA cm−2, respectively. Tafel slope is as low as 78.44 mV dec−1, and favorable electrochemical stability can be maintained for at least 50 h. The strategy may provide valuable references for future researchers to prepare better MOF-based electrocatalysts.

CoCx‑induced interfacial octahedral Co2+ sites of NiCo-LDH electrode with improved faradic reactivity toward high-performance supercapacitor

Battery-like electrode materials are characterized by large theoretical capacitance but suffer from poor surface reactivity and insufficient electroactive sites thus limiting their practical charge storage capacity. To overcome this challenge, an effective strategy for vacancy modulation on battery-like electrode materials is necessary. Herein, we report for the first time an elaborately designed three-dimensional (3D) hierarchical heterostructure consisting of CoCx@NiCo-LDH on conductive nickel foam as a freestanding supercapacitor electrode. Benefiting from the weakening of the coordination of CoO bonds, the CoCx structure induces in-situ reconstruction of the NiCo-LDH lattice, resulting in the formation of abundant oxygen vacancies (interfacial octahedral Co2+ sites) that lower the OH− adsorption energy as determined by the density functional theory (DFT) calculation. The resulting CoCx@NiCo-LDH/NF electrode exhibits an ultrahigh rate capability (2330 mF cm−2 at 0.3 mA cm−2, with capacitance retention of 51.5 % at 30 mA cm−2) and remarkable cycling performance (capacitance retention of 81.6 % after 10,000 cycles). Additionally, the assembled asymmetric devices deliver an extremely high energy density of 246 μWh cm−2 at the power density of 798 μW cm−2, with 87.8 % capacitance retention after 10,000 cycles at 8 mA cm−2. Overall, this study presents a simple yet effective strategy to construct high-performance battery-like electrodes for potential applications in energy storage, transportation, and communication.

Outstanding electrochemical performance of nickel-cobalt phosphate sheets with abundant mesopores for use in aqueous asymmetric supercapacitors and Ni–Zn batteries

Transition metal phosphate materials (TMPs), especially bimetallic phosphates, have been regarded as an attractive electrode material for energy storage applications. However, phosphate materials with high capacitance and long cycle stability have scarcely been reported in the literature, due to their poor conductivity and small surface area. In this work, novel mesoporous nickel-cobalt phosphate sheets supported on conductive nickel foam (NF) have been successfully prepared by a facile and straightforward hydrothermal reaction. The resulting material shows a particularly attractive electrochemical performance, with a fairly high specific capacitance of 3722 F g−1 (7.44 F cm−2) at a current density of 1 A g−1. Even at current density values of 25 A g−1, the specific capacitance remains sufficiently high, that is, 1900 F g−1 (3.8 F cm−2). The significantly improved capacitance of nickel-cobalt phosphate material arises from the effective combination of the synergistic effect between two metal species, abundant mesopores and the high specific area of sheets, contributing to faster electrochemical kinetics, shortening ion transport channels and providing plentiful active sites for reaction. Furthermore, an asymmetric supercapacitor device using nickel-cobalt phosphate as cathode electrode and activated carbon (AC) as anode electrode has been assembled. This device exhibits a prominent energy density of 57.22 Wh kg−1 at a power density of 400 W kg−1 and excellent cycling performance at a large current density of 30 A g−1 (about 98% capacitance retention for 30000 cycles). Surprisingly, nickel-cobalt phosphate sheets firstly applied in an aqueous Ni–Zn battery deliver a high capacity of 195.5 mAh g−1 at 1 A g−1 and good rate performance (104.6 mAh g−1 at 10 A g−1). Such experimental findings suggest that mesoporous nickel-cobalt phosphate sheets are candidate materials to be employed in aqueous supercapacitors and Ni–Zn batteries.

Synergetic modulation of a hierarchical nanoflower-like NiMoO4/Ni(OH)2 composite toward efficient alkaline water oxidation

Electrocatalysts with densely exposed sites and high intrinsic activity are desired for high-efficiency oxygen evolution reaction (OER). In this paper, we report the microwave assisted solvothermal growth of NiMoO4 nanoflowers on electrodeposited Ni(OH)2 nanosheets, forming a high specific surface area (132.5 m2g-1) nanoflower-like NiMoO4/Ni(OH)2 configuration supported on a conductive nickel foam (NF) substrate. The as-prepared NiMoO4/Ni(OH)2/NF behaved efficiently as a self-supported 3D catalyst electrode for alkaline OER, compared with commercial RuO2 (298 mV overpotential at 10 mA cm−2 and Tafel slope of 88.6 mV dec−1), needing a low overpotential of 292 mV to attain 10 mA cm−2, with a small Tafel slope of 85.0 mV dec−1 and good stability for 100 h running at 10 mA cm−2 in 1.0 M KOH. Aside from enlarged surface area for more exposed edge sites for catalysis, the modulated synergy between Ni and Mo atoms probably contributes to enhanced intrinsic activity. A more electronegative Mo increases the electron density of Ni, thus accelerating the deprotonation of intermediates and driving the transition from Ni to NiOOH, leading to modulated thermodynamics and kinetics for OER catalysis.

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.