Bimetallic Synergistic Effect Research Articles

Dual optimization strategy assisted m-phenylenediamine-based hypercrosslinked polymer loaded ultrafine bimetallic nanoparticles for efficient formic acid dehydrogenation

Heterogeneous catalysts based on Pd play a vital role in enabling efficient formic acid decomposition (FAD). Nevertheless, the performance of Pd-based catalysts is constrained by inherent challenges, such as Pd particles’ tendency to aggregate and possess localized electronic structures. Therefore, there is an urgent need to develop an effective strategy to simultaneously overcome these challenges. In response to this, we synthesized knitting hypercrosslinked polymers (HCPs) using m-phenylenediamine (MPD) as the aromatic monomer. A dual-optimization approach was proposed, aiming to mitigate the adverse effects of excessive coordination and maximize the involvement of residual Fe3+ in the bimetallic synergistic effect. Experimental findings, DFT calculations, and ab initio molecular dynamics simulations (AIMDs) collectively suggest that reducing the coordination effect leads to enhanced nitrogen exposure in the HCPs, consequently reducing the size of Pd species. Furthermore, the incorporation of residual Fe3+ into Pd forms Pd-Fe bimetallic species, which then adjusts the catalytic reaction barrier and enhances catalytic activity. Notably, the optimized Pd@MHCP-2 catalyst exhibited exceptional performance in the FAD reaction at 323 K, achieving a remarkable turnover frequency (TOF) value of 1486 h−1. This research introduces a novel perspective for the design and development of next-generation Pd-based catalysts.

Ultrathin ternary PtNiRu nanowires for enhanced oxygen reduction and methanol oxidation catalysis via d-band center regulation

Direct methanol fuel cells rely on the efficiency of their anode/cathode electrocatalysts to facilitate the methanol oxidation reaction and oxygen reduction reaction, respectively. Platinum-based nanocatalysts are at the forefront due to their superior catalytic properties. However, the high-cost, scarcity, and low CO tolerance of platinum pose challenges for the scalable application of DMFCs. Herein, we report novel ultrathin ternary PtNiRu alloy nanowires to improve Pt utilization and CO tolerance. These novel electrocatalysts incorporate the oxophilic metal Ru into ultrathin PtNi nanowires, aiming to enhance the intrinsic activity of platinum while leveraging the long-term durability and high utilization efficiency provided by the bimetallic synergistic effect. The PtNiRu NWs significantly enhance both mass activity and specific activity for ORR, performing about 6.9 times and 3.9 times better than commercial Pt/C, respectively. After a rigorous durability test of 10,000 cycles, the PtNiRu NWs only exhibited a 25.2 % loss in mass activity. Additionally, for MOR, the MA and SA of PtNiRu NWs exceed that of Pt/C catalyst by 4.30 and 2.72 times, respectively, and exhibit exceptional resistance to CO poisoning. Theoretical insights from density functional theory calculations suggest that the introduction of Ru modulates the d-band center of the surface Pt atoms, which contributes to decreased binding strength of oxygenated species and an elevated dissolution potential, substantiating the enhanced performance metrics, and the durability enhancement stems from the stronger PtM bonds than those in PtNiRu NWs resulted from PtRu covalent interactions. These findings not only provide a new perspective on platinum-based nanocatalysts but also significantly advance the quest for more efficient and durable electrocatalysts for DMFCs, representing a substantial stride in fuel cell technology.

Preparation of presulfided oil-soluble NiMo catalyst for slurry bed hydrocracking of vacuum residue

Here, a method is proposed for constructing presulfided oil-soluble NiMo catalysts using tetrathiomolybdate nickel ammonium as a precursor via a chelating ligand exchange strategy. Leveraging the close chemical bonding between Ni and Mo atoms, the NiMo catalyst can undergo in-situ self-sulfidation to generate active NiMoS sites and a composite structure of Ni3S2 and MoS2 nano phase in tight contact, thus exhibiting strong synergistic effects. The NiMo catalyst exhibited outstanding performance in hydrocracking of vacuum residue (VR) achieving a 64.7 wt% VR conversion while maintaining a coke yield of 0.51 wt%, as well as the excellent hydrogenation activity of polycyclic aromatic hydrocarbons. Combined with density functional theory calculations, it was further revealed that the presence of Ni reduces the energy barrier for H2 dissociation on MoS2, thereby enhancing the hydrogenation activity of the catalyst and its ability to suppress coke formation. This work validates the efficient bimetallic synergistic catalytic effect of presulfided oil-soluble NiMo catalysts in the slurry bed hydrocracking process.

Facile fabrication of Au-Ag alloy nanoparticles/Ag nanowires SERS substrates with bimetallic synergistic effect for ultra-sensitive detection of crystal violet and alkali blue 6B

The bimetallic nanostructure of Au and Ag can integrate two distinct properties into a novel substrate compared to single metal nanostructures. This work presents a rapid and sensitive surface-enhanced Raman scattering (SERS) substrate for detecting illegal food additives and dyes of crystal violet (CV) and alkali blue 6B (AB 6B). Au-Ag alloy nanoparticles/Ag nanowires (Au-Ag ANPs/Ag NWs) were prepared by solid-state ionics method and vacuum thermal evaporation method at 5μA direct current electric field (DCEF), the molar ratio of Au to Ag was 1:18.34. Many 40 nm-140 nm nanoparticles regularly existed on the surface of Ag NWs with the diameters from 80 nm to 150 nm. The fractal dimension of Au-Ag ANPs/Ag NWs is 1.69 due to macroscopic dendritic structures. Compared with single Ag NWs, the prepared Au-Ag ANPs/Ag NWs substrates show superior SERS performance because of higher surface roughness, the SERS active of Ag NWs and bimetallic synergistic effect caused by Au-Ag ANPs, so the limit of detections (LOD) of Au-Ag ANPs/Ag NWs SERS substrates toward detection of CV and AB 6B were as low as 10-16mol/L and 10-9mol/L, respectively. These results indicate that Au-Ag ANPs/Ag NWs substrates can be used for rapid and sensitive detection of CV and AB 6B and have great development potential for detection of illegal food additives and hazardous substances in the fields of environmental monitoring and food safety.

Constructing Metal-Organic Framework Films with Adjustable Electronic Properties on Hematite Photoanode for Boosting Photogenerated Carrier Transport.

Hematite (α-Fe2O3) has become a research hotspot in the field of photoelectrochemical water splitting (PEC-WS), but the low photogenerated carrier separation efficiency limits further application. The electronic structure regulation, such as element doping and organic functional groups with different electrical properties, is applied to alleviate the problems of poor electrical conductivity, interface defects, and band mismatch. Herein, α-Fe2O3 photoanodes are modified to regulate their electric structures and improve photogenerated carrier transport by the bimetallic metal-organic frameworks (MOFs), which are constructed with Fe/Ni and terephthalate (BDC) with 2-substitution of different organic functional groups (─H, ─Br, ─NO2 and ─NH2). The α-Fe2O3 photoanode loaded with FeNi-NH2BDC MOF catalyst exhibits the optimal photocurrent density (2mAcm-2) at 1.23VRHE, which is 2.33 times that of the pure α-Fe2O3 photoanode. The detailed PEC analyses demonstrate that the bimetallic synergistic effect between Fe and Ni can improve the conductivity and inhibit the photogenerated carrier recombination of α-Fe2O3 photoanodes. The ─NH2 group as an electron-donor group can effectively regulate the electron distribution and band structure of α-Fe2O3 photoanodes to prolong the lifetime of photogenerated holes, which facilitates photogenerated carrier transport and further enhances the PEC-WS performance of α-Fe2O3 photoanode.

Bimetallic synergistic effect of Co and Fe for the highly efficient catalytic decomposition of ozone

AbstractGround‐level ozone pollution is a major concern for human health, ecosystems, and material degradation. This article presents a Co‐ and Fe‐based bimetallic layered double hydroxide (CoFe‐LDH) catalyst for ozone decomposition. The CoFe‐LDH catalyst exhibited 100% ozone decomposition efficiency over 24 h at a reaction rate of 35.3 μmol g−1 min−1. The synergetic effects between Co and Fe regulated the valence state, increased the number of Co vacancies, and increased the specific surface area and density of the hydroxyl groups on the surface. Moreover, the two metals facilitated different dissociation steps and the desorption step became exothermic after ozone enrichment on the surface, rendering every step concurrently spontaneous, which has not been observed in previously reported ozone decomposition catalysts. This study demonstrates the potential of LDHs for ozone pollution control and offers new insights into the design of synergistic bimetallic catalysts.

Enhanced catalytic reduction of 4-nitrophenol using bimetallic MOFs: a one-pot synthesis approach

ABSTRACT Several organic pollutants can harm the environment and human health. A typical environmentally toxic contaminant, 4-Nitrophenol (4-NP), may cause serious health issues. Therefore, catalytic reduction (hydrogenation) of 4-nitrophenol into less toxic 4-aminophenol (4-AP) is mostly preferred. A three-dimensional (3D) metal-organic framework of Ni-MOF-74 is mostly used which contains maximum unsaturated metal sites and the catalytic activity is enhanced due to partial exchange at the node position in MOF. In order to study the catalytic hydrogenation/reduction of organic dye, 4-nitrophenol as a model reaction, a bimetallic MOF, FeNi-MOF-74 was prepared by partially substituting Ni with Fe metal. The catalyst was synthesised using a one-pot solvothermal technique, and 4-nitrophenol was then reduced catalytically in aqueous media. For the reduction of nitrophenol, the FeNi-MOF-74 catalyst surpassed Ni-MOF (9.3 × 10−3 s−1) and Fe-MOF (5.4 × 10−3 s−1) with a lower reduction time and a higher rate constant; (1.6 × 10−2 s−1). The high conversion rate and economical induction time are attributed to the bimetallic synergistic effect.

AuPt bimetallic loaded defect state g-C3N4 enhances photocatalytic H2 evolution: Exploring synergistic effects and charge transfer mechanisms

AuPt alloy nanoparticles (NPs) were prepared using a simple photodeposition method to modify defective state g-C3N4 nanosheets (HCN) which contained N vacancies, B doping, and CN groups. The visible diffuse reflectance spectra (DRS) indicate that AuPt/HCN exhibits high light absorption capability. The photoluminescence spectrum (PL) and steady-state surface photovoltage (SPV) indicate that AuPt/HCN possesses a high rate of photogenerated charge separation and a high efficiency of photogenerated electron transfer. The electrochemical tests indicate that AuPt/HCN exhibits lower electrochemical impedance. AuPt/HCN (1.0 wt%) exhibits outstanding photocatalytic hydrogen evolution efficiency, producing hydrogen at a rate of 2095 μmol·g−1·h−1 under visible light, which is 2.10 times and 1.55 times higher than that of monometallic Au/HCN (1.0 wt%) (997 μmol·g−1·h−1) and Pt/HCN (1.0 wt%) (1349 μmol·g−1·h−1), respectively. The bimetallic synergistic effect of AuPt alloy NPs co-catalysts enhances the photocatalytic hydrogen evolution activity of AuPt/HCN composite photocatalysts.

Confinement and synergy effects of supported-confined bimetal catalysts with superior stability and catalytic activity

Bimetallic nanocrystals have attracted considerable attention because of their complicated systems, which are far superior to those of their individual constituents. A TiO2-confined PtMnP bimetallic catalyst (PtMnP@TiO2) was prepared using an ultrasonic-assisted coincident strategy, which demonstrated exceptional catalytic activity in the universal hydrogen evolution reaction (HER). Owing to the bimetallic synergistic effect and TiO2 confinement, PtMnP@TiOx showed ultrasmall metal nanoparticles (NPs), a higher active Pt0 content, adequate activation at the porous surface, and abundant acid sites. Simulations were performed to visualize the strain properties of Mn and Pt during the bending process and demonstrate the high activity of Pt. The Pt-Mn bimetallic catalysts were enriched with Pt NPs, convoyed by electron transfer from Mn to Pt. Briefly, PtMnP@TiO2 showed robust evolution reaction activities (an overpotential of 220 mV at a current density of 10 mA cm−2 and a Tafel slope of 186 mV dec−1) and the ability to contrast stated catalysts without ultrasonication-plasma. This protocol revealed that the geometrical and electronic effects of Pt and P surrounding the Mn species in PtMnP@TiO2 were crucial for increasing the catalytic activity (99%) and durability (over 20 cycles), which were far superior to those of other reported catalysts.

Fabrication of three-dimensional hierarchical NiCo-LDH micro-flowers for enhanced charge storage in battery-type supercapacitors

Layered double hydroxides (LDHs) show great advantage in supercapacitors (SCs) due to their unique layered structure and high theoretical capacity. However, their poor electrical conductivity and structural instability hinder their practical application. Metal-organic framework materials (MOFs) can be utilized to construct transition metal derived materials with adjustable morphology and high electrochemical properties. In this study, we first synthesized flower-like NiCo-based MOFs (NiCo-BTC) using a one-step solvothermal reaction. The formation process followed a sequence of “nucleation-growth-etching” corresponding to Ostwald's maturation theory. Subsequently, novel hierarchical NiCo-LDHs micro-flowers were constructed through treating the NiCo-BTC in an alkaline solution. The morphology of NiCo-LDHs was optimized by adjusting the ratio of Ni to Co, so as to achieve excellent electrochemical properties due to the hierarchical flower-like structure and the bimetallic synergistic effect. As a result, Ni3Co1-LDH exhibited a high specific capacitance of 1978.2 F/g at 1 A/g, excellent rate capability of 82.80 % at 40 A/g and good cycle stability with 70.6 % capacitance retention after 10,000 cycles at a high current density of 10 A/g. Furthermore, the asymmetric SC (ASC) based on Ni3Co1-LDH//AC exhibited high specific capacitance of 162.4 F/g at 1 A/g and excellent energy density of 54.8 Wh/kg at power density of 779.4 W/kg. In addition, the ASC demonstrated remarkable cycle stability with a capacitance retention of 96.5 % after 3500 cycles. The successful synthesis of 3D hierarchical NiCo-LDHs micro-flowers offers an effective approach to developing highly promising electrodes for SCs.

Metal polyphenol network structure regulated Fe2O3-CeO2/PC for the enhanced electro-Fenton-like remediation of organic wastewater in a widely applicable pH range

Developing efficient Fenton and Fenton-like systems for the remediation of organic wastewater remains a challenge for the limited applicable pH range and sluggish kinetics. In this study, a novel electro-Fenton-like system was constructed for the efficient degradation of multiple organic pollutants based on Fe-Ce bimetallic oxide supported on porous carbon (Fe2O3-CeO2/PC) heterogeneous catalyst, which was prepared by annealing metal polyphenol network structure (MPNs) regulated Fe-Ce-tannic acid (TA) complexes. The Fe2O3-CeO2/PC-based system showed higher removal rate (93.6 %) and apparent rate constant (0.021 min−1) for tetracycline (TC) as compared to the MPNs-free Fe2O3-CeO2 system (79.1 %, 0.011 min−1), catalyst-free system (59.3 %, 0.007 min−1) and adsorption system (66.7 %, 0.009 min−1). Under the optimal conditions, the as-proposed electro-Fenton system showed a high removal rate of ∼ 95 % to the typical phenol, dye and antibiotics. After 240 min’ electrolysis, the removal rates of COD and TOC reached 93.7 % and 58.7 %, respectively. After 5 cycles’ degradation, the removal rate of TC didn’t show obvious decline in performance (remained at about ∼ 90 %). More importantly, the system can effectively remove TC in simulated wastewater in a broad pH range of 3–11, which was much superior to the other electro-Fenton-like systems. The satisfactory degradation performance of the electro-Fenton-like system based on MPNs-regulated Fe2O3-CeO2/PC was attributed to the strong coordination ability between TA and the metal species in the heterogeneous catalyst and the bimetallic synergistic effect on optimizing the electronic configuration of Fe2O3-CeO2/PC, which accelerated the redox cycles of ≡TA-Fe(Ⅲ)/≡TA-Fe(II) and ≡TA-Ce(Ⅳ)/≡TA-Ce(III) as electron shuttles and facilitated the production of sufficient ROS (mainly O2·− and 1O2) for the degradation and mineralization of the organic pollutants. Based on the produced intermediates, the feasible degradation pathways of the representative TC occurred in Fe2O3-CeO2/PC-based electro-Fenton-like system were inferred. This work lays an important theoretical foundation for the rational design of high-performance electrocatalysts and electro-Fenton/electro-Fenton-like systems, enabling the efficient remediation of organic wastewater.

Modulating composition and electronic structure enhance the catalytic performance of Co2MO4 (M=Fe, Ni, Cu) for NaBH4 hydrolysis

The synergistic effect between metals is of great significance for improving the performance of materials, but the mechanism of synergistic catalytic of bimetallic has rarely been reported in the hydrolysis of sodium borohydride (NaBH4, SB). In this paper, a flower shaped Co2FeO4 catalyst with high catalytic performance was selected from a series of CoxM3-xO4 (M = Fe, Ni, Cu) catalysts by controlling the composition. Based on the results of XPS characterization and density functional theory (DFT) calculation, the influence of component control on catalytic performance was discussed and explained from the perspective of electronic structure, and the "valence band center" and "D-band center" descriptors were introduced into the SB hydrolysis reaction. The simulation analysis results showed that the synergistic effect between Co–Fe elements resulted in the smallest center shift of the D band, the smallest binding energy of the hydrolysis reaction, and the best promoting effect on the electronic structure, manifested as the best catalytic performance. The calculation results were consistent with the XPS characterization results and the experimental results of hydrolysis performance testing, revealing the principle of bimetallic synergistic effect on catalytic performance.

Guanine-derived core-shell FeCo alloy confined in graphene-like N-doped carbon as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

Maximization the synergistic effect of each component in transition metal-carbon complexes is expected to improve the bifunctional oxygen electrocatalysis for rechargeable Zn-air batteries but is still challenging. Herein, nucleobase guanine is employed as a supramolecular precursor to generate the core (FeCo alloy)-shell (carbon) structure embedded in ultrathin graphene-like nitrogen-doped carbon nanosheets (FeCo@NCNSs) via a confinement pyrolysis strategy. Thanks to the generated core-shell structure and bimetallic synergistic effect, the as-prepared FeCo@NCNSs exhibits excellent electrochemical performance in both oxygen reduction reaction and oxygen evolution reaction. As a result, when served as the bifunctional air electrode for a practical Zn-air battery, FeCo@NCNSs exhibits a higher open-circuit voltage (1.553 V) and peak power density (197.30 mW cm−2), as well as the greatly improved long-term cyclic stability compared to the noble metal benchmarks. This work provides a promising approach to integrate various active sites for bifunctional oxygen electrocatalysis and inspires the exploration of simple but efficient electrocatalysts for energy storage and conversion.

Selective degradation of organic pollutants by highly dispersed Fe, Ni anchored on nitrogen carbon activating persulfate system: Electron transfer promotion, the impact of pollutant redox and adsorption properties

The advanced oxidation processes using persulfate (PS-AOPs) as oxidant is an effective way to remove refractory organic pollutants from environment. Designing activators with higher activation efficiency and stability plays an important role in degradation of organic pollutants via PS-AOPs. Furthermore, redox and adsorption properties of pollutants also affect the selective degradation efficiency. In this study, we synthesized FeNi@CN derived from ZIF-8 in which highly dispersed Fe and Ni were anchored on nitrogen (N) doped carbon (C). The activator exhibited high activation potential and stability for paracetamol (PCT) degradation by activated peroxymonosulfate (PMS). The FeNi@CN/PMS system degraded PCT through electron transfer pathway, and the coordination of Fe-N and Ni-N improved the efficiency of catalyst mediated electron transfer. The abundant pyridinic N provided a large number of sites for PMS complexation. The bimetallic synergistic effect and N doping endowed the excellent comprehensive performance of FeNi@CN. The significant impact of pollutant redox and adsorption properties on degradation efficiency were also studied. It was observed that high half-wave potential (E1/2) and excessive adsorption were not conducive to electron transfer. Multi-parameter linear fitting was performed on the degradation rates of different pollutants using half-wave potential and pseudo first order adsorption rate constants, which showed the good correlation among them. This work not only provided insights into the mechanism and the influence of activator structure on electron transfer in PMS activation, but also proposed a new model to describe the effects of redox and adsorption properties on selective degradation of various category pollutants.

CoNi hexacyanoferrate nanoparticles anchored on carbon nanotubes as superior cathode materials for rechargeable aqueous zinc-ion batteries

Prussian blue analogues (PBAs) have attracted growing interest as competitive cathode materials for aqueous zinc-ion batteries (AZIBs). However, their low conductivity and easy structural collapse often lead to poor reversible capacity and cyclability. Herein, cobalt‑nickel hexacyanoferrate (CoNiHCF), a CoNi-Prussian blue analogue, are designed as AZIBs cathode materials for the first time, in which highly uniform CoNiHCF nanocubes are in-situ decorated on carbon nanotubes (CNTs) via a simple co-precipitation method. The resulted CoNiHCF/CNTs composite displays superior zinc ion storage performance, with a great reversible capacity of 124.9 mAh g−1 at the current density of 50 mA g−1, and a high capacity retention of 81.8 % at 3000 mA g−1 for 1000 cycles, which are remarkably superior to those of CoHCF, NiHCF and CoNiHCF. The excellent Zn2+ storage properties of CoNiHCF/CNTs can be ascribed to the bimetallic synergistic effect of Co and Ni as well as the introduction of conductive CNTs skeleton. This study offers a straightforward and efficient method for promoting the application of PBAs-based cathodes in AZIBs.

Bimetallic Co-Mn catalysts for synergistic enhancement of VOC gas-sensing performance of ZnO hierarchical nanostructures.

The synergistic effect between bonding dissimilar metals is a very effective way to improve the performance of metal catalysts. In this work, we prepared a series of bimetallic co-doped ZnO hierarchical nanostructures by controlling Mn and Co contents. The gas-sensing properties of the sensors based on the bimetallic co-doped ZnO hierarchical nanostructures were studied systematically through different volatile organic compound (VOC) vapors for the temperature range from 160 to 400 °C. In the testing of normal butanol gas by the bimetallic co-doped ZnO sensor, its performance was tens of times higher than that of pure zinc oxide, and the response values to other VOCs tested were very low, which also indicates that the sensor has good selectivity. The promoted performance is attributed to the increase of adsorbed oxygen content on the surface of the sensor material due to the bimetallic synergistic enhancement effect. XPS spectra of O 1s region of the sensor show that the adsorbed oxygen content is 22.4%, which is higher than that of the pure ZnO (8.5%). The synergistic effect between bimetallic Mn and Co leads to electron enrichment on the surface of ZnO. Electron enrichment can not only promote the activation of ZnO, but also can help to improve the gas-sensing performance.

Facile synthesis of a CeMnOx catalytic gel with bacterial microenvironment-responsive antibacterial properties

pH-responsive, H2O2 self-supplying properties and bimetallic synergistic effects enhance the catalytic antibacterial properties of the CeMnOx hydrogel.

Doping Ni into CoB achieves surface reconstruction to promote efficient electrocatalytic hydrogen evolution reaction

The effective advancement of skilled transition metal electrocatalysts is crucial for promoting the hydrogen evolution reaction (HER) in the process of water splitting. In this context, the integration of nickel (Ni) transition metal atoms into cobalt boride (CoB) is achieved through an electrochemical deposition approach, yielding a remarkably active electrocatalyst termed Ni@CoB for HER. At 10 mA cm−2, the HER overpotential is 63 mV with a Tafel slope of 64.73 mV dec-1. After 50 h of stability testing, there was no significant current decay observed. By employing material characterization techniques and DFT calculations, it has been shown that the incorporation of Ni leads to a surface reconstruction of CoB, thereby decreasing surface aggregation. The catalyst exhibits a uniform spherical porous structure, facilitating enhanced electron transfer. The doped Ni atoms form a bimetallic synergistic effect with Co atoms, not only increasing the stability of interatomic covalent bonds but also enhancing reaction kinetics. This study illuminates the influence of incorporating transition metal atoms into CoB on the activity of HER, presenting a promising strategy for designing high-performance catalysts for alkaline hydrogen evolution.

Synergistically catalytic regulation of surface chemistry on coal based needle coke by bimetallic interface for enhanced Li/Na storage

The oxygen functional groups (OFGs) on carbon surface are electrochemically active for rapid Li/Na storage, and always are introduced with environment-hazardous and time-consuming ways. Herein, the bimetallic synergistic effect between Fe and Ni metal nanoparticles is proved experimentally to promote the conversion from useless C–O groups to useful CO groups on the surface of needle coke (NC) greatly. In addition, the DFT calculations show that introducing second metals increase the active electrons of single metals, and the activity of transforming C–O bond to CO bond thus makes a difference in bimetallic systems. Among the modified samples, Fe/Ni-NC contains abundant CO groups, stripe like graphite domains, excellent electronic conductivity and large interlayer spacing. Therefore, Fe/Ni-NC anode shows the excellent capacities in half batteries (212/305.2 mA h g−1 after 1000/2000 cycles at 2.0/5.0 A g−1 in SIB/LIB) and full batteries (86/145 mA h g−1 in SIB/LIB at 0.05 A g−1 after 100 cycles), significantly better than other carbon materials. The work provides a practical and significant reference to regulate precisely the surface energy storage active sites of coal based carbon material, aiming at advanced SIB and LIB.

Ni2CoS4@(NiCo)Se2 bimetallic selenides with core–shell heterostructure in-situ generated on Ni2CoS4 nanorods arrays for high performance supercapacitors

In this paper, Ni2CoS4@(NiCo)Se2/NF core–shell structural nanocomposites are successfully prepared on nickel foam (NF) substrates through a convenient hydrothermal method and tube furnace calcination. Firstly, NiCo2O4/NF is acquired by a one-step simple hydrothermal method and one-step tube furnace calcination, then it is sulfidated via a one-step hydrothermal method, and finally selenized by stirring to obtain Ni2CoS4@(NiCo)Se2/NF. The results show that in the three-electrode test, the specific capacitance of the Ni2CoS4@(NiCo)Se2 electrode is able to reach 6054 mF·cm−2 at a current density of 10 mA·cm−2. The excellent performance of Ni2CoS4@(NiCo)Se2/NF nanocomposites is supposed to give rise to the bimetallic synergistic effect, as well as the unique core–shell structure of its surface-loaded nanosheets. In addition, all-solid-state asymmetric supercapacitors (ASCs) are composed of activated carbon (AC) as the anode and Ni2CoS4@(NiCo)Se2/NF as the cathode. The prepared Ni2CoS4@(NiCo)Se2/NF//AC ASC devices reach an energy density of 53 Wh kg−1 at a power density of 480 W kg−1. Simultaneously, Ni2CoS4@(NiCo)Se2/NF//AC ASC device has an excellent specific capacitance of 149.06F g−1 at a current density of 0.6 A/g and a capacitance retention rate of 84.0 % after 10,000 electrochemical cycles, which proves its good cycling stability. Impressively, two Ni2CoS4@(NiCo)Se2/NF//AC ASC devices connected in series can light up a 2.5 V LED lamp and continue to illuminate it for 11 min. Our results show that Ni2CoS4@(NiCo)Se2/NF nanocomposites with core–shell structures have great application potential in energy storage devices.