3D Interconnected Architecture Research Articles

Interconnected CoNi-Se Hollow Flakes through Reduced Graphene Oxide Sheets as a Cathode Material for Hybrid Supercapacitors.

Achieving a high energy density and long-cycle stability in energy storage devices demands competent electrochemical performance, often contingent on the innovative structural design of materials under investigation. This study explores the potential of transition metal selenide (TMSe), known for its remarkable activity, electronic conductivity, and stability in energy storage and conversion applications. The innovation lies in constructing hollow structures of binary metal selenide (CoNi-Se) at the surface of reduced graphene oxide (rGO) arranged in a three-dimensional (3D) morphology (CoNi-Se/rGO). The 3D interconnected rGO architecture works as a microcurrent collector, while porous CoNi-Se sheets originate the active redox centers. Electrochemical analysis of CoNi-Se/rGO based-electrode reveals a distinct faradic behavior, thereby resulting in a specific capacitance of 2957 F g-1 (1478.5 C g-1), surpassing the bare CoNi-Se with a value of 2149 F g-1 (1074.5 C g-1) at a current density of 1 A g-1. Both materials exhibit exceptional high-rate capabilities, retaining 83% of capacitance at 10 A g-1 compared to 1 A g-1. In a two-electrode coin cell system, the device achieves a high energy density of 73 Wh kg-1 at a power density of 1500 W kg-1, stating an impressive 90.4% capacitance retention even after enduring 20,000 cycles. This study underscores the CoNi-Se/rGO composite's promise as a superior electrode material for high-performance energy storage applications.

Three-dimensional interconnected graphene architecture reinforced epoxy composite with superior mechanical and tribological properties

The tribological performances reinforcement is limited by insufficient dispersion and random orientation of nanofillers in composites. In light of above difficulties, a three-dimensional (3D) interconnected graphene architecture (3DGA) was designed, in which the reinforcement is pre-formed in three dimensions. In the 3DGA reinforced epoxy composite (3DGA/EP) fabricated by resin transfer molding combined with in-situ ultrasonic method, 3DGA assembling from graphene sheets was in good dispersion and distribution state, which resulted in exceptional thermal stability, mechanical and tribological properties for epoxy composites. Compared with graphene oxide (GO)/EP composites in direct solution blending, glass transition temperature and tensile strength of the 3DGA/EP composites increased by 27.1 °C and 41.1 %, and wear rate decreased by 38.1 %, respectively. In this work, 3DGA was utilized as the ordered reinforcement of composites instead of two-dimensional graphene sheets, providing a promising strategy to achieve high-performance polymer-based composites with superior mechanical and tribological properties.

Binder- and conductive additive-free Ga2O3 nanowires as a self-healing anode for lithium storage

High-capacity anode materials have stimulated much attention to developing high-performance lithium-ion batteries. However, high-capacity anode materials commonly suffer from the pulverization matter that greatly hinders their practical applications, especially in terms of the high proportion of active materials. In this work, a Ga2O3 nanowire electrode is synthesized by thermal evaporation and immediately used as an anode without the aid of binders and conductive additives. The 3D interconnected architecture of the Ga2O3 nanowire electrode shortens lithium diffusion lengths and expedites reaction kinetics. The Ga2O3 nanowires exhibit high elasticity and a self-healing ability which is inherited from metallic Ga formed during the electrochemical transition process, thus circumventing the formidable pulverization issue to a certain extent. Benefiting from the unique structural, mechanical, and chemical attributes, the as-grown Ga2O3 nanowire electrode gives a high initial lithiation capacity of 1462 mAh g−1 under a current density of 0.1 ​A ​g−1. It delivers good cyclic stability with a reversible capacity of 445 mAh g−1 after 200 cycles at 0.5 ​A ​g−1. Furthermore, the investigation of lithium storage behaviors indicates the high rate capability of Ga2O3 nanowires. This paper contributes to understanding binder- and conductive additive-free electrodes consisting of high-capacity active materials from various viewpoints.

Enhanced strength and toughness of Ni/graphene composite via three-dimensional graphene-like nanosheets network

This paper reports a novel strategy for fabricating the three-dimensional graphene-like nanosheets network (3D-GLNN) in a nickel (Ni) matrix composite through spark plasma sintering induced welding between graphene-like nanosheets grown on the surface of Ni foams. The in-situ constructed 3D interconnected GLNN architecture can significantly improve the load transfer capacity, thereby increasing the yield strength of the bulk composite. The crack bridging in the fracture process induced by the 3D-GLNN blocks the crack propagation during tensile deformation and results in significant strengthening and toughening. This study provides an innovative design idea (using the 3D-connected Ni foam as a template) to synergistically enhance the strength and strain-hardening capacity, thereby breaking the strength-ductility trade-off of graphene-reinforced metal matrix composites.

Tuning pyridinic-N and graphitic-N doping with 4,4′-bipyridine in honeycomb-like porous carbon and distinct electrochemical roles in aqueous and ionic liquid gel electrolytes for symmetric supercapacitors

Doping engineering in nanostructured carbon materials is an effective approach to modify heteroatom species and surface electronic structures. Herein, an advanced electrode material based on a honeycomb-like porous carbon matrix with tunable N-doped configurations is prepared via 4,4′-bipyridine (4,4′-bpy)-assisted pyrolysis of SiO2@ZIF-8 templates and subsequent etching treatment. Interestingly, the amounts of pyridinic-N and graphitic-N can be controlled by rationally varying the content of 4,4′-bpy which acts as the N source in the pyrolysis process. Both experimental results and density functional theory calculations have revealed that synergistically with 3D interconnected porous architecture, pyridinic-N and graphitic-N have different effects on the electrochemical performances in aqueous and ionic liquid gel electrolytes for symmetric supercapacitors. Highly exposed pyridinic-N endows the carbon electrode with a strengthened pseudocapacitance contribution manifested as a high specific capacitance of 436.1 F g−1 and exceptional stability of almost 100% capacitance retention after 5000 cycles at 10 A g−1 in the KOH/polyvinyl alcohol (PVA) electrolyte. By contrast, graphitic-N is propitious for reinforced electrical double-layer capacitance contribution, reflected by a maximum energy density of 125.4 Wh kg−1 in the 1-ethyl-3-methylimidazolium tetrafluoroborate/poly(vinylidene fluoride-co-hexafluoropropylene) (EMIMBF4/PVDF-HFP) electrolyte. This work offers an in-depth insight into the understanding of the energy storage mechanism of N-rich carbon electrodes in different electrolyte media.

A Three-Dimensionally Interconnected Composite Polymer Electrolyte for Solid-State Batteries

High energy density of solid-state batteries requires a thin solid electrolyte separator layer (<30 μm), that can sustain high currents and is easily processable. Polymer-ceramic composite electrolytes can potentially fulfill these requirements by combining the advantages of each type. Ceramic electrolytes have high room-temperature ionic conductivity, transference number of one, and mechanical strength to suppress lithium dendrites, whereas polymer electrolytes are easily processable and can form conformable interfaces with the electrodes. High interfacial-impedance between polymer and ceramic electrolytes make the composites with dispersed ceramic particles less attractive.1 A composite electrolyte architecture where a three-dimensionally interconnected porous ceramic is filled with polymer electrolyte, previously reported by our group, can avoid the interfacial impedance issue, although for thin composite membranes, the interfacial impedance between ceramic framework and excess polymer layer on top/bottom surface will still dominate the overall impedance.2 Here we will present fabrication and electrochemical evaluation of ~150 μm thick composite electrolytes with the above-described 3D-interconnected ceramic architecture. The 3-D framework is obtained by partially sintering Ohara ceramic particle tapes obtained via tape casting, which are filled with curable polymer electrolyte precursors. To obtain a thin (5 μm), uniform polymer electrolyte layer on both surfaces, spray coating was employed. The resulting composite membrane exhibited good dendritic resistance in symmetric cell cycling, improved transference number compared to the polymer electrolytes. We also found significantly improved flexibility of the composite electrolytes with plasticization, however, at the cost of reduction in ionic conductivity due to damage to the ceramic network caused by plasticizer-induced swelling of the cross-linked polymer electrolyte. This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office’s Advanced Battery Materials Research Program (Tien Duong, Program Manager). This abstract has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). References Chen, X. C.; Liu, X.; Samuthira Pandian, A.; Lou, K.; Delnick, F. M.; Dudney, N. J., Determining and Minimizing Resistance for Ion Transport at the Polymer/Ceramic Electrolyte Interface. ACS Energy Letters 2019, 4 (5), 1080-1085.Palmer, M. J.; Kalnaus, S.; Dixit, M. B.; Westover, A. S.; Hatzell, K. B.; Dudney, N. J.; Chen, X. C., A three-dimensional interconnected polymer/ceramic composite as a thin film solid electrolyte. Energy Storage Materials 2020, 26, 242-249.

High performance supercapacitors using selenium partially reduced Co3O4 on carbon cloth electrode with 3D interconnected architecture nanowires

The electrodes with high conductivity, large specific surface area and homogeneous pore size distribution are greatly desirable for supercapacitors applications. Herein, a hydrothermal and subsequent annealing approach was adopted to fabricate 3D interconnected nanowires architecture of selenium partially reduced spinel Co3O4 grew on the carbon cloth (COS@CC). The binder-free COS@CC electrode displays excellent specific capacitance, 1046.9 C g−1 at 1 A g−1, superior rate capability, 51.6% capacitance retention and superior cyclic stability, 92.0% capacitance retention after 15,000 cycles. These electrochemical performances were found to be better than that of the Co3O4@CC electrode. The enhanced electrochemical performance was ascribed to the fact that 3D interconnected architecture nanowires could shorten the ion transfer distance and heighten the rate of the redox reaction. In addition, increased specific surface area and homogeneous mesopore size distribution could assist effective diffusion and transfer of OH– between electrodes and electrolyte. The enhancement of conductivity, which is caused by the selenium partial reduction and more oxygen vacancies in the structure, facilitates electrons transfer and consequently improves the electrochemical properties of supercapacitors. These remarkable electrochemical performances indicate that the CSO@CC can be employed for developing high-energy and power-density supercapacitors.

Highly reversible Zn metal anodes enabled by multifunctional poly zinc acrylate protective coating

The application of low-cost and high-safety aqueous Zn metal batteries is seriously hindered by Zn anode stemming from its uncontrollable dendrite growth and detrimental water-induced side reactions. Herein, a zinc-enriched and negatively charged poly zinc acrylate (PZA) polyelectrolyte with hydrophobic 3D network is firstly constructed on Zn surface through facile UV light irradiation of ZA monomer. The as-obtained PZA coating exhibits a strong adhesion to Zn foil, persistently protecting Zn from water corrosion. Furthermore, the 3D interconnected network architecture favors the fast transport of Zn2+. Meanwhile, the anions can be shielded and desolvation of hydrated Zn2+ is accelerated. Notably, the self-contained Zn2+ in PZA can avoid the supply of sluggish ions. Accordingly, the Zn@PZA anode delivers a low energy barrier and high Zn2+ transference number. Moreover, it endows a superior Coulombic efficiency of 99.7 % and long-life dendrite-free plating/stripping (10 mA cm−2, 2 mAh cm−2). The MnO2||Zn@PZA full cell displays a highly stable cycling behavior for over 700 cycles with a high capacity retention of 95.1 % at 1 A/g together with a satisfactory rate performance. This work delivers an affordable and facile strategy to realize the high reversibility and stability of Zn anodes.

Poly(butylene succinate) matrices obtained by thermally-induced phase separation: Pore shape and orientation affect drug release

Poly(butylene succinate) (PBS) scaffolds with 3D microporous interconnected architecture and crystallized PBS substructures have been prepared by thermally-induced phase separation (TIPS). Curcumin (CUR) and piperine (PIP) natural drugs were incorporated into the matrices during a one-step fabrication protocol. Alterations in TIPS parameters such as solvent system (1,4 dioxane (DXN) or THF) and cooling condition (intensity and direction of thermal gradient) affected the phase separation process and the scaffold properties. Controlling the crystallization of DXN in a uniaxial direction, resulted in the formation of microtubular scaffolds with oriented porosities. Well-developed PIP crystals and matrix-integrated CUR agglomerates were uniformly distributed throughout the scaffolds. The integration of CUR to the polymer matrix was confirmed by physicochemical evaluations, attributed to a possible interaction with PBS, resulting in a slower release than PIP. The scaffolds with uniaxially-oriented porosities displayed a greater sustained release (only 50–60% after 170 h) due to the restricted drug diffusion through their dense spherulitic pore walls. Due to such structure and smoother well-arranged surfaces, the oriented scaffolds also exhibited greater biocompatibility. Our results reveal the positive influence of TIPS-derived structural orientation on properties of PBS matrices for cell/drug delivery. • Controlling the porous architecture is crucial to designing cell/drug carriers. • Porosity orientation affects the final properties of the polymeric matrix. • Herein, porosity orientation has been controlled by adjusting TIPS thermal gradient. • Uniaxially-aligned pores had spherulitic and denser walls compared to random ones. • Such a structure could impede the drug diffusion, being achieved a sustained release.

TEMPO-mediated oxidized cellulose nanofibers-Cd2+ derived hierarchically porous carbon aerogel for oxygen reduction electrocatalysis

• TOCNFs-Cd 2+ aerogel is constructed via the electrostatic and ionic interactions. • Cd metal acts as the thermally sacrificial template to generate ultralight N-CNA-Cd. • N -CNA-Cd has abundant micro-/meso-pores, rich defects, huge SBET and fibrous network. • An impressive ORR electrocatalytic efficacy was obtained on N-CNA-Cd sample. Carbon aerogel (CA) emerges as a kind of burgeoning material platform for electrocatalysis with merits of the 3D porous and interconnected architecture to facilitate the low-resistant mass diffusion and charge transport. There still remain great challenges in fine-tuning the intrinsic chemical nature and creating hierarchically porous microstructure in CA through a sustainable synthesis route. Here, we employed TEMPO-mediated oxidized cellulose nanofibers (TOCNFs) and a thermally sacrificial template Cd metal with low boiling point (767 °C) to assemble TOCNFs-Cd 2+ hydrogel/aerogel, which is then subsequently converted to ultralight N -doped carbon nanofibers aerogel ( N -CNA-Cd) upon pyrolysis at a moderate temperature. Thanks to the presence of abundant interior micro- and meso-pores, rich defects, huge BET specific surface area (1782 m 2 g −1 ) and interconnected fibrous network, the as-obtained N -CNA-Cd samples demonstrate an impressive electrocatalytic efficacy towards oxygen reduction reaction in terms of the positive half-wave potential (0.84 V), large electrochemical active surface area and considerable stability under both alkaline and acidic conditions. This study provides a versatile strategy for designing and engineering carbonaceous aerogels that can be suited for electrocatalysis and energy storage applications from renewable plant cellulose resources.

Asymmetric supercapacitors based on porous MnMoS4 nanosheets-anchored carbon nanofiber and N, S-doped carbon nanofiber electrodes

Electrode materials with high electrochemical activity and a favorable morphology are highly desired for improving the energy density of supercapacitors. A ternary metal sulfide with higher electrochemical activity and capacity than mono-metal sulfides offers immense promise as an energy storage material. In the present investigation, an advanced flexible hybrid electrode material composed of porous manganese molybdenum sulfide (MnMoS4) nanosheets supported on flexible carbon nanofiber (CNF) mat has been prepared via three sequential steps: (i) electrospinning, (ii) stabilization/carbonization, and (iii) hydrothermal reaction. Advantages from the rich electrochemical redox properties of MnMoS4 and the 3D interconnected network architecture of porous CNF mat, a large specific capacitance of 2187.5 F/g (at 1 A/g), and a good capacity retention ability (>87%) were achieved for the MnMoS4 @CNF hybrid electrode. In addition, asymmetric supercapacitor (ASC) devices were assembled by utilizing two different binder-free electrodes, i.e., MnMoS4 @CNF mat as the positive electrode and N, S doped CNF mat as the negative electrode, and evaluated their capacitive performances in two different electrolytes, i.e., KOH and Na2SO4. As-assembled ASC with 1 M Na2SO4 electrolyte delivered a high energy density of 72.5 Wh kg−1 and a power density of 2.7 kW kg−1 together with a capacity retention of 93.5% after 5000 cycles. The overall outcome of this investigation indicates that the binder-free nanostructured MnMoS4 @CNF hybrid mat has great potential for the development of next-generation supercapacitor devices.

3D interconnected network architectures assembled from W18O49 and Ti3C2 MXene with excellent electrochemical properties and CDI performance

W18O49 has been demonstrated to be a promising candidate for efficient electrochemical applications. To further improve the electrical conductivity of W18O49 and make it suitable for hybrid capacitive deionization (HCDI), highly stable three-dimensional (3D) interconnected network architectures assembled from W18O49 and Ti3C2 MXene composites with different Ti3C2 contents have been synthesized via a facile and effective electrostatic attraction self-assembly strategy and used as a novel HCDI electrode material. Compared to single-component electrodes, the synergistic effect between W18O49 and Ti3C2 enabled high specific surface area (SSA), fast ion diffusion, and dual pseudocapacitance effect. These multiple advantages of the W18O49/Ti3C2 electrode achieved a preponderant salt adsorption capacity (SAC) as high as 29.25 mg g−1 in 500 mg L−1 NaCl solution at an applied voltage of 1.2 V. An excellent capacitance (153F g−1 at 2 mV s−1) and high cycling stability (maintaining 98.3% of the initial capacity after 10 cycles) were also observed. This work could provide some insights for rational design of 3D electrode architectures for electrochemical applications and water desalination.

3D hierarchical Ti3C2TX @NiO-reduced graphene oxide heterostructure hydrogel as free-standing electrodes for high performance supercapacitor

2D MXenes have been brought into sharp focus in electrochemical energy-storage devices due to their excellent electronic conductivity, high specific surface area, tunable layer structure, and large redox-active surface areas. Nevertheless, further applications of MXenes as electrode materials for supercapacitors are severely limited by the low theoretical specific capacity and self-restacking. Herein, a Ti3C2TX @NiO heterostructure is constructed firstly by uniformly deposition of NiO nanosheets on Ti3C2TX substrate, then the composite is incorporated into 3D porous hydrogel via an efficient graphene oxide (GO)-assisted self-convergence hydrothermal strategy with low temperatures. Owing to the synergistic effect among each components and the 3D porous interconnected architecture, the resultant 3D hierarchical Ti3C2TX @NiO-Reduced Graphene Oxide (RGO) heterostructure hydrogel not only takes both merits of highly conductive and outstanding pseudocapacitive, but also significantly prevents the aggregation and increases the surface utilization of Ti3C2TX @NiO. The 3D hierarchical Ti3C2TX @NiO-RGO heterostructure hydrogel electrodes (without binders) exhibit an enhanced electrochemical performance, with a superb specific capacitance up to 966 F g−1 at 1 A g−1 and long-term stability of 94.5% over 10,000 cycles. Importantly, a maximum energy density of 58.5 Wh kg−1 is obtained at power density of 550 W kg−1. Our work provides a facile and efficient approach to develop Ti3C2TX-based heterostructure hydrogels with improved overall performance, which expands the practical applications of MXenes in supercapacitors.

An efficient cooling solution with 3D interconnected graphene architectures for passive heat dissipation

A 3D hybridized reduced graphene oxide membrane (AR-rGO) was fabricated using a convenient electrochemical deposition method, which possesses a highly efficient passive heat dissipation capability.

Flexible nickel disulfide nanoparticles-anchored carbon nanofiber hybrid mat as a flexible binder-free cathode for solid-state asymmetric supercapacitors

Nickel disulfide nanoparticles (NiS2NPs)-anchored carbon nanofibers (NiS2NPs@CNF) hybrid mats were fabricated via the sequential process of stabilization and carbonization of electrospun polyacrylonitrile-based fibers followed by hydrothermal growth of NiS2NPs on the porous surface of CNFs. The vertical growth of NiS2NPs on entire surfaces of porous CNFs appeared in the SEM images of hybrid mat. The hierarchical NiS2NPs@CNF core–shell hybrid nanofibers with 3D interconnected network architecture can endow continuous channels for easy and rapid ionic diffusion to access the electroactive NiS2NPs. The conductive and interconnected CNF core could facilitate electron transfer to the NiS2 shell. Moreover, the porous CNF as a buffering matrix can resist volumetric deformation during the long-term charge–discharge process. The NiS2NPs@CNF electrode can yield high specific capacitance (916.3 F g−1 at 0.5 A g−1) and reveal excellent cycling performances. The solid-state asymmetric supercapacitor (ASC) was fabricated with NiS2NPs@CNF mat as a binder-free positive electrode and activated carbon cloth as a negative electrode. As-assembled ASC not only produce high specific capacitance (364.8 F g−1 at 0.5 A g−1) but also exhibit excellent cycling stability (∼92.8% after 5000 cycles). The ASC delivered a remarkably high energy density of 129.7 Wh kg−1 at a power density of 610 W kg−1. These encouraging results could make this NiS2NPs@CNF hybrid mat a good choice of cathode material for the fabrication of flexible solid-state ASC for various flexible/wearable electronics.

Three-Dimensional Engineering of Sulfur/MnO2 Composites for High-Rate Lithium-Sulfur Batteries.

Herein, a three-dimensional interconnected sulfur (3DIS) system is used to construct a cathode of the lithium-sulfur battery. Compared with the traditional methods of encapsulating sulfur, the 3DIS system serves as a framework to grow MnO2, which ensures a high sulfur content of 91.5 wt % (the ratio of sulfur/host was 10.8) and a uniform distribution of sulfur. Due to the synergistic effect of the 3D interconnected architecture and the uniform coating layer of polar MnO2, 3DIS@MnO2 (3DISMO) delivers a capacity of 891 mA h g-1 after 900 cycles at 1 C. Even at a rate of 10 C, a capacity decay rate of 0.061% per cycle is achieved.

Defect-rich and metal-free N, S co-doped 3D interconnected mesoporous carbon material as an advanced electrocatalyst towards oxygen reduction reaction

Researching of high performance and low-cost oxygen reduction reaction (ORR) electrocatalysts is one of the core issues for the rapid development of energy conversion and storage devices. Herein, a N and S dual-doped three-dimensional (3D) interconnected mesoporous carbon catalyst (CNS) was constructed via a facile hydrothermal-pyrolysis strategy. Benefiting from the 3D interconnected mesoporous architecture, CNS was endowed with a fast oxygen mass transfer rate together with plentiful of accessible active centers on the surface. Its ORR half-wave potential (E1/2， 0.87 V) surpasses commercial Pt/C catalyst 50 mV in alkaline media. Its E1/2 negatively shifts only 2 mV after 8000 cycles in half-cell tests. More importantly, the zinc-air battery with CNS as cathode catalyst delivers an excellent high peak power density of 144 mW cm−2. DFT calculation results show that when N and S are co-doped, the spin density of adjacent carbon atoms can be changed, thereby increasing the CNS's binding energy to oxygen and conductivity. The excellent comprehensive performance of CNS undoubtedly discloses its potential practical application in the energy conversation and storage area.

Mesoporous Fe‐Nx‐C Sub‐Microspheres for Highly Efficient Electrocatalytic Oxygen Reduction Reaction

AbstractWe design and obtain mesoporous Fe‐Nx‐C sub‐microspheres (Meso Fe‐Nx‐C‐SS) using the amino acid‐metal complex as Fe/N/C precursor and mesoporous silica sub‐microspheres (MSS) as hard template by a facile template‐assistance strategy. The Histidine‐Fe complex is impregnated into mesopores of MSS, and then Meso Fe‐Nx‐C‐SS are obtained by high‐temperature carbonization process and removal of MSS template. The as‐fabricated Meso Fe‐Nx‐C‐SS exhibits the spherical structure with rough surface with the diameter size of 200–500 nm. And Meso Fe‐Nx‐C‐SS also possesses a high specific surface area of 784 m2 g−1, a large pore volume of 1.65 cm3 g−1, and a large pore size in the range of 10–22 nm. Benefiting from atomically dispersed N‐coordinated Fe and unique three‐dimensionally (3D) interconnected mesoporous carbon architecture, Meso Fe‐Nx‐C‐SS shows excellent electrocatalytic performance toward oxygen reduction reaction (ORR) with positive half‐wave potential (E1/2 0.86 V), high stability (93.94 % after 30,000 s), low Tafel slop (43 mV dec−1) and good methanol tolerance, exceeding commercial Pt/C catalyst in alkaline media. As the cathode catalyst within the primary Zn‐air batteries, Meso Fe‐Nx‐C‐SS also reveals an outstanding catalytic activity (the maximum power density of 120 mW cm−2) and superior discharge stability (at current density of 10 mA cm−2 after 6 cycles, at different current densities of 5, 10, 20 mA cm−2), promoting its practical application in Zn‐air batteries.

Carbon nanotubes interpenetrating MOFs-derived Co-Ni-S composite spheres with interconnected architecture for high performance hybrid supercapacitor

Recently, carbon nanotubes (CNT)-based interconnected architectures exhibit promising prospects in supercapacitors due to their flexibility and high electrical conductivity. Herein, a three-dimensional (3D) interconnected network structure combined with conductive carbon nanotubes interpenetrating MOFs-derived Co-Ni-S composite spheres (Co-Ni-S/CNTs) was synthesized. Such 3D interconnected architecture significantly leads to a favorable electronic structure, fast charge-transfer capacity, and more pseudocapacitive. The Co-Ni-S/CNTs-based hybrid electrode exhibits an extraordinary specific capacitance of 540.6C g−1 at 1 A g−1 and competitive rate performance (capacity retention rate of 69.9% when the current density increases to 10 times). Subsequently, a hybrid supercapacitor is assembled using Co-Ni-S/CNTs as the positive electrode and commercial activated carbon as negative electrode. The device delivers a high energy density of 63.5 W h kg−1 at 800 W kg−1 and keeps 83.0% initial capacitance retention after 10,000 cycles. The encouraging performances demonstrate the significant contribution of the 3D interconnected architecture for the future energy storage.

Oxygen Reduction Reaction Performance Boosting Effect of Nitrogen/Sulfur Co-Doped Graphene Supported Cobalt Phosphide Nanoelectrocatalyst: pH-Universal Electrocatalyst

Herein, a novel noble metal-free hybrid of CoP@N,S-3D-GN in which cobalt phosphide (CoP) anchored onto the nitrogen and sulfur co-doped three-dimensional graphene(N,S-3D-GN) architecture is proposed to catalyze the oxygen reduction reaction (ORR) both in acidic and alkaline media. The facile cost-effective fabrication strategy including hydrothermal self-assembly of 3D–GN and subsequent low-temperature phosphidation is implemented. The obtained hybrids exhibit pH-universal electrocatalytic activity towards ORR thanks to facilitated mass diffusion, boosted charge transport, and abundance of electroactive sites as a result of the synergistic effect of co-doped heteroatoms and metal phosphide nanoparticles. The virtues of large specific surface area and 3D-interconnected microporous and mesoporous architecture, as well as tailoring of the surface with CoP and N,S-co-doping, facilitate the ORR catalytic activity and offer four-electron pathways both in acidic (n = 3.962) and alkaline media (n = 3.991). CoP@N,S-3D-GN offered long-term stability with 91.8% and 82.8% retention of initial current after 25,000 s in 0.1 M KOH and 0.1 M HClO4 electrolytes, respectively. The boosted electrocatalytic performance of CoP@N,S-3D-GN puts forward its up-and-coming usage of noble metal-free electrocatalysts alternative to platinum-group metals for ORR. This work paves the way for designing the next generation electrocatalysts for renewable energy systems due to the intriguing features including pH-universal catalytic activity, satisfactory durability, relatively low-cost and scalable production method.