Designing transition metal-based porous architectures for supercapacitor electrodes: a review.

Over the past decade, transition metal (TM)-based electrodes have shown intriguing physicochemical properties and widespread applications, especially in the field of supercapacitor energy storage owing to their diverse configurations, composition, porosity, and redox reactions. As one of the most intriguing research interests, the design of porous architectures in TM-based electrode materials has been demonstrated to facilitate ion/electron transport, modulate their electronic structure, diminish strain relaxation, and realize synergistic effects of multi-metals. Herein, the recent advances in porous TM-based electrodes are summarized, focusing on their typical synthesis strategies, including template-mediated assembly, thermal decomposition strategy, chemical deposition strategy, and host-guest hybridization strategy. Simultaneously, the corresponding conversion mechanism of each synthesis strategy are reviewed, and the merits and demerits of each strategy in building porous architectures are also discussed. Subsequently, TM-based electrode materials are categorized into TM oxides, TM hydroxides, TM sulfides, TM phosphides, TM carbides, and other TM species with a detailed review of their crystalline phase, electronic structure, and microstructure evolution to tune their electrochemical energy storage capacity. Finally, the challenges and prospects of porous TM-based electrode materials are presented to guide the future development in this field.

Stability of Multivalent Ruthenium on CoWO4 Nanosheets for Improved Electrochemical Water Splitting with Alkaline Electrolyte.

Engineering low-cost electrocatalysts with desired features is vital to decrease the energy consumption but challenging for superior water splitting. Herein, we development a facile strategy by the addition of multivalence ruthenium (Ru) into the CoWO4 /CC system. During the synthesis process, the most of Ru3+ ions were insinuated into the lattice of CoWO4 , while the residual Ru3+ ions were reduced to metallic Ru and further attached to the interface between carbon cloth and CoWO4 sheets. The optimal Ru2 (M)-CoWO4 /CC exhibited superior performance for the HER with an overpotential of 85 mV@10 mA cm-2 , which was much better than most of reported electrocatalysts, regarding OER, a low overpotential of 240 mV@10 mA cm-2 was sufficient. In comparison to Ru2 (0)-CoWO4 /CC with the same Ru mass loading, multivalence Ru2 (M)-CoWO4 /CC required a lower overpotential for OER and HER, respectively. The Ru2 (M)-CoWO4 /CC couple showed excellent overall water splitting performance at a cell voltage of 1.48 V@10 mA cm-2 for used as both anodic and cathodic electrocatalysts. Results of the study showed that the electrocatalytic activity of Ru2 (M)-CoWO4 /CC was attributed to the in-situ transformation of Ru/Co sites, the multivalent Ru ions and the synergistic effect of different metal species stimulated the intrinsic activity of CoWO4 /CC.

Bimetallic Metal-Organic Framework-Derived Pomegranate-like Nanoclusters Coupled with CoNi-Doped Graphene for Strong Wideband Microwave Absorption.

Metal-organic frameworks (MOFs) featuring high porosity and tunable structure make them become promising candidates to fabricate carbon-based microwave absorption (MA) materials to meet the requirements of electronic reliability and defense security. However, it is challenging to rationally design a well-organized micro-nanostructure to simultaneously achieve strong and wideband MA performance. Herein, a three-dimensional (3D) hierarchical nanoarchitecture (CoNi@NC/rGO-600) comprising pomegranate-like CoNi@NC nanoclusters and ultrasmall CoNi-decorated graphene has been successfully fabricated to broaden the absorption bandwidth and enhance the absorption intensity. The results confirm that the bimetallic MOF CoNi-BTC-derived pomegranate-like CoNi@NC nanoclusters with porous carbon shell as "peel" and sub-5 nm CoNi nanoparticles as "seeds" favor multiple polarization, magnetic loss, and impedance matching. Moreover, the interconnected 3D CoNi-doped graphene acts not only as a bridge to connect pomegranate-like CoNi@NC nanoclusters but also as a conductive network to supply multiple electron transportation paths. Consequently, the optimized CoNi@NC/rGO-600 exhibits extraordinary MA performance in terms of wide bandwidth (6.7 GHz) and strong absorption (-68.0 dB). As an effective strategy, this work provides a new insight into fabricating hierarchical composite structures for advancing MA performances and other applications.

In Situ Confined Bimetallic Metal-Organic Framework Derived Nanostructure within 3D Interconnected Bamboo-like Carbon Nanotube Networks for Boosting Electromagnetic Wave Absorbing Performances.

Metal-organic framework (MOFs) derived magnetic nanoparticles/porous carbon (M/C) composites featuring efficient interfacial engineering and spatially continuous three-dimensional (3D) networks are desirable electromagnetic wave (EMW) absorbing materials due to multiple transmission path and well impedance matching. However, it is challenging to construct such 3D interconnected carbon networks from a single MOF precursor. Herein, FeNi3 and N embedded 3D carbon networks comprising bamboo-like carbon nanotubes connected carbon nanorods (FeNi@CNT/CNRs) were prepared via one-step pyrolyzing of the composite of melamine and FeNi-MIL-88B. Attributed to the synergistic contributions of 3D interconnected carbon nanotube networks and MOFs derived M/C for multiple transmission path, impedance matching, and dielectric loss (especially for multiple polarization and micro-current), the FeNi@CNT/CNRs nanoarchitectures have demonstrated superior EMW absorbing performance. In particular, the optimized FeNi@CNT/CNR-0.9 has exhibited strong absorption (-47.0 dB, 2.3 mm in thickness) and broadband effective absorption (4.5 GHz, 1.6 mm in thickness). This attractive strategy holds promise as a general approach to fabricate the carbon hybrid network constituted of MOFs derived nanopolyhedron and CNTs for the target application.

Cactus-Inspired Bimetallic Metal-Organic Framework-Derived 1D-2D Hierarchical Co/N-Decorated Carbon Architecture toward Enhanced Electromagnetic Wave Absorbing Performance.

Metal-organic framework (MOF)-derived magnetic metal/carbon nanocomposites have shown tremendous potential for lightweight electromagnetic wave (EMW) absorption. However, it is a challenge but highly significant to design and construct mixed-dimensional hierarchical architectures with synergistically integrated characteristics from individual MOFs for advancing the EMW absorption performance. Inspired by the structure of cactus, a novel hierarchical one-dimensional (1D)-two-dimensional (2D) mixed-dimensional Co/N-decorated carbon architecture comprising carbon nanotubes grafted on carbon flakes (abbreviated as CoNC/CNTs) has been fabricated by the pyrolysis of bimetallic CoZn-ZIF-L. The CoNC/CNTs integrate the advantages of 1D nanotubes for the extra polarization of EMW and 2D nanoflakes with an interconnected porous structure for multiple reflection losses of EMW and optimization of impedance matching. The resultant CoNC/CNTs demonstrate excellent EMW absorbing performance. For the optimal EMW absorbing material of CoNC/CNT-3/1, minimum reflection loss reaches -44.6 dB at 5.20 GHz with a low filler loading of 15 wt %. Moreover, the largest effective bandwidth range achieves 4.5 GHz with a thickness of 1.5 mm and a filled ratio of 20 wt %. These findings indicate that such a mixed 1D-2D hierarchical architecture synergistically enhances EMW absorbing performance. This work sheds light on the rational design of a mixed-dimensional carbon architecture derived from MOFs for desirable functionalities.

Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles.