Carbon nanocages bridged with graphene enable fast kinetics for dual-carbon lithium-ion capacitors

Lithium-ion capacitors(LICs) combining the advantages of lithium-ion batteries and supercapacitors are considered a promising nextgeneration energy storage device. However, the sluggish kinetics of battery-type anode cannot match the capacitor-type cathode, restricting the development of LICs. Herein, hierarchical carbon framework(HCF) anode material composed of 0D carbon nanocage bridged with 2D graphene network are developed via a template-confined synthesis process. The HCF with nanocage structure reduces the Li^(+) transport path and benefits the rapid Li^(+) migration, while 2D graphene network can promote the electron interconnecting of carbon nanocages. In addition, the doped N atoms in HCF facilitate to the adsorption of ions and enhance the pseudo contribution, thus accelerate the kinetics of the anode. The HCF anode delivers high specific capacity, remarkable rate capability. The LIC pouch-cell based on HCF anode and active HCF(a-HCF) cathode can provide a high energy density of 162 Wh kg^(-1) and a superior power density of 15.8 kW kg^(-1), as well as a long cycling life exceeding 15,000cycles. This study demonstrates that the well-defined design of hierarchical carbon framework by incorporating 0D carbon nanocages and 2D graphene network is an effective strategy to promote LIC anode kinetics and hence boost the LIC electrochemical performance.

Heterostructuring noble-metal-free 1T'phase MoS_(2) with g-C_(3)N_(4) hollow nanocages to improve the photocatalytic H2 evolution activity

In this work,we report the preparation of 1T'-MoS_(2)/g-C_(3)N_(4) nanocage(NC)heterostructure by loading 2D semi-metal noble-metal-free 1T'-MoS_(2) on the g-C_(3)N_(4) nanocages(NCs).DFT calculation and experimental data have shown that the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure has a stronger light absorption capacity and larger specific surface area than pure g-C_(3)N_(4) NCs and g-C_(3)N_(4) nanosheets(NSs),and the presence of the co-catalysts 1T'-MoS_(2) can effectively inhibit the photoinduced carrier recombination.As a result,the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure with an optimum 1T'-MoS_(2) loading of 9 wt%displays a hydrogen evolution rate of 1949 mmol h^(-1) g^(-1),162.4,1.2,1.5,1.6 and 1.2 times than pure g-C_(3)N_(4) NCs(12 mmol h^(-1) g^(-1)),Pt/g-C_(3)N_(4) NCs(1615 mmol h^(-1) g^(-1))and Pt/g-C_(3)N_(4) nanosheets(NSs,1297 mmol h^(-1) g^(-1)),1T'-MoS_(2)/g-C_(3)N_(4) nanosheets(1216 mmol h^(-1) g^(-1))and 2H-MoS_(2)/g-C_(3)N_(4) nanocages(1573 mmol h^(-1) g^(-1)),respectively,and exhibits excellent cycle stability.Therefore,1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure is a suitable photocatalyst for green H_(2) production.

Hierarchical sulfur and nitrogen co-doped carbon nanocages as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

Exploring inexpensive and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is critical for rechargeable metal-air batteries. Herein, we report a new 3D hierarchical sulfur and nitrogen co-doped carbon nanocages(hSNCNC) as a promising bifunctional oxygen electrocatalyst by an in-situ MgO template method with pyridine and thiophene as the mixed precursor. The as-prepared h SNCNC exhibits a positive half-wave potential of 0.792 V(vs. reversible hydrogen electrode, RHE) for ORR, and a low operating potential of 1.640 V at a 10 mA cm-2 current density for OER. The reversible oxygen electrode index is 0.847 V, far superior to commercial Pt/C and IrO2,which reaches the top level of the reported bifunctional catalysts. Consequently, the hSNCNC as air cathodes in an assembled Zn-air battery features low charge/discharge overpotential and long lifetime. The remarkable properties arises from the introduced multiple heteroatom dopants and stable 3D hierarchical structure with multi-scale pores, which provides the abundant uniform high-active S and N species and efficient charge transfer as well as mass transportation. These results demonstrate the potential strategy in developing suitable carbon-based bi-/multi-functional catalysts to enable the next generation of the rechargeable metal-air batteries.

Architecture of Co-layered double hydroxide nanocages/graphene composite electrode with high electrochemical performance for supercapacitor

A facile hydrolysis method was applied to fabricate high-performance Co-layered double hydroxide（LDH）nanocages/graphene composites for supercapacitors. The materials exhibit enhanced rate capability than the counterpart electrode free of graphene while maintaining a high specific capacitance. In addition,such Co-LDH nanocages/graphene composites display an excellent cycling stability; the capacitance retention of Co-LDH nanocages/graphene composite electrode remains 90.4% after 10000 cycles at a current density of 2 A g（-1）. The integration of high capacity of double hydroxide and outstanding conductivity of graphene makes the delicately-designed composites promising candidates for electrode materials for supercapacitors.

Hierarchical N-doped carbon nanocages/carbon textiles as a flexible O2 electrode for Li–O2 batteries

The conventional Li–O2 battery(LOB)has hardly been considered as a next-generation flexible electronics thus far,since it is bulk,inflexible and limited by the absence of an adjustable cell configuration.Here,we present a flexible Li–O2 cell using N-doped carbon nanocages grown onto the carbon textiles(NCNs/CTs)as a self-standing and binder-free O2 electrode.The highly flexible NCNs/CTs exhibits an excellent mechanic durability,a promising catalytic activity towards the ORR and OER,a considerable cyclability of more than 70 cycles with an overpotential of 0.36 V on the 1 stcycle at a constant current density of 0.2 m A/cm2,a good rate capability,a superior reversibility with formation and decomposition of desired Li2 O2,and a highly electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible LOBs.

Hollow Nanocages of Ni_(x)Co_(1-x)Se for Efficient Zinc–Air Batteries and Overall Water Splitting

Developing Earth-abundant,highly efficient,and anticorrosion electrocatalysts to boost the oxygen evolution reaction(OER),oxygen reduction reaction(ORR),and hydrogen evolution reaction(HER) for the Zn–air battery(ZAB) and for overall water splitting is imperative.In this study,a novel process starting with Cu2O cubes was developed to fabricate hollow NixCo1-xSe nanocages as trifunctional electrocatalysts for the OER,ORR,and HER and a reasonable formation mechanism was proposed.The Ni0.2Co0.8Se nanocages exhibited higher OER activity than its counterparts with the low overpotential of 280 mV at 10 mA cm-2.It also outperformed the other samples in the HER test with a low overpotential of 73 mV at 10 mA cm-2.As an air–cathode of a self-assembled rechargeable ZAB,it exhibited good performance,such as an ultralong cycling lifetime of > 50 h,a high round-trip efficiency of 60.86%,and a high power density of 223.5 mW cm-2.For the application in self-made all-solid-state ZAB,it also demonstrated excellent performance with a power density of 41.03 mW cm-2 and an open-circuit voltage of 1.428 V.In addition,Ni0.2Co0.8Se nanocages had superior performance in a practical overall water splitting,in which only 1.592 V was needed to achieve a current density of 10 mA cm-2.These results show that hollow NixCo1-xSe nanocages with an optimized Ni-to-Co ratio are a promising cost-effective and high-efficiency electrocatalyst for ZABs and overall water splitting in alkaline solutions.

Preparation of vapreotide-templated silver nanocages and their photothermal therapy efficacy

Vapreotide acetate （Vap） was used as a biotemplate to synthesize silver nanocages through direct co-incubation of a AgNO3 solution, following by reduction using fresh NaBH4. The characterized vapreotide-templated silver nanocages （Vap-AgNCs） presented a wide and red shifted absorption band with a maximum between 480 nm and 800 nm and possessed a uniform structure with a face-centered cubic crystal structure. The biocompatibiliW of Vap-AgNCs was assessed using the MTT method, indicating Vap-AgNCs had better biocompatibility when its concentration was lower than 2,5 × 10-4 mmol. L- 1. The photothermal characteristics of Vap-AgNCs were analyzed with laser irradiation （808 nm, 1,5 W, cm-2） and the results showed that the temperature of the Vap- AgNCs solution reached 45 ℃ starting from 25 ℃ within 5 min. Additionally, Vap-AgNCs with a laser led to HeLa cell death. Therefore, the prepared Vap-AgNCs is expected to be an effective photothermal therapy agent.

Laser-induced convenient fabrication of CdS nanocages with super-adsorption capability for methyl blue solution

We report on the successful synthesis of cadmium sulfide （CdS） nanocages by laser ablation of bulk Cd target in thioacetamide （TAA） solution. The CdS nanocages exhibit obvious interior hollow spaces and distinctive porous-shell structures. After laser ablation of Cd target in liquid condition, the unique structure should be attributed to the initial forma- tion of Cd micro-gas bubble via a model of micro-explosive boiling model. Surprisingly, the obtained CdS nanocages can provide a super-adsorption of methyl blue （MB） solution. The maximum adsorption capacity reaches up to 11813.3 mg/g, which is much higher than that reported in many previous researches. Without using any complicated stabilizers or soft directing agents, the pure CdS nanocages fabricated by laser ablation will serve as advanced absorbents in further research.

A direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

Given the increasing number of diabetic patients,rapid and accurate detection of glucose in body fluids is critical.This study developed a direct electrochemical biosensor for glucose based on nitrogen-doped carbon nanocages(NCNCs).NCNCs possess a large specific surface area of 1395 m^(2)·g^(-1),a high N atomic content of 9.37%and good biocompatibility,which is favorable for enzyme loading and electron transfer.The surface average concentration of electroactive glucose oxidase on NCNCs was 2.82×10^(-10)mol·cm^(-2).The NCNC-based direct electrochemical biosensor exhibited a high sensitivity of 13.7μA·(mmol·L^(-1))^(-1)·cm^(-2),rapid response time of 5 s and an impressive electron-transferrate constant(ks)of 1.87 s^(-1).Furthermore,we investigated an NCNC-based direct electron transfer(DET)biosensor for sweat glucose detection,which demonstrated tremendous promise for non-invasive wearable diabetes diagnosis.

Ultrasmall high-entropy alloy nanoparticles on hierarchical N-doped carbon nanocages for tremendous electrocatalytic hydrogen evolution

High-entropy alloys (HEAs) are promising candidates for the electrocatalyst of hydrogen evolution reaction (HER) due to their unique properties such as cocktail electronic effect and lattice distortion effect. Herein, the ultrasmall (sub-2 nm) nanoparticles of PtRuCoNiCu HEA with uniform element distribution are highly dispersed on hierarchical N-doped carbon nanocages (hNCNC) via low-temperature thermal reduction, denoted as us-HEA/hNCNC. The optimal us-HEA/hNCNC exhibits excellent HER performance in 0.5 M H_(2)SO4 solution, achieving an ultralow overpotential of 19 mV at 10 mA·cm^(−2) (without iR-compensation), high mass activity of 13.1 A·mgnoble metals ^(−1) at −0.10 V and superb stability with a slight overpotential increase of 3 mV after 20,000 cycles of cyclic voltammetry scans, much superior to the commercial Pt/C (20 wt.%). The combined experimental and theoretical studies reveal that the Pt&Ru serve as the main active sites for HER and the CoNiCu species modify the electron density of active sites to facilitate the H* adsorption and achieve an optimum M-H binding energy. The hierarchical pore structure and N-doping of hNCNC support also play a crucial role in the enhancement of HER activity and stability. This study demonstrates an effective strategy to greatly improve the HER performance of noble metals by developing the HEAs on the unique hNCNC support.

Alloyed Pt-Sn nanoparticles on hierarchical nitrogen-doped carbon nanocages for advanced glycerol electrooxidation

Glycerol is an alternative sustainable fuel for fuel cells,and efficient electrocatalyst is crucial for glycerol oxidation reaction(GOR).The promising Pt catalysts are subject to the inadequate capability of C-C bond cleavage and the susceptibility to poisoning.Herein,Pt-Sn alloyed nanoparticles are immobilized on hierarchical nitrogen-doped carbon nanocages(hNCNCs)by convenient ethylene glycol reduction and subsequent thermal reduction.The optimal Pt_(3)Sn/hNCNC catalyst exhibits excellent GOR performance with a high mass activity(5.9 A·mg_(Pt)^(-1)),which is 2.7 and 5.4 times higher than that of Pt/hNCNC and commercial Pt/C,respectively.Such an enhancement can be mainly ascribed to the increased anti-poisoning and C-C bond cleavage capability due to the Pt_(3)Sn alloying effect and Sn-enriched surface,the high dispersion of Pt_(3)Sn active species due to N-participation,as well as the high accessibility of Pt_(3)Sn active species due to the three-dimensional(3D)hierarchical architecture of hNCNC.This study provides an effective GOR electrocatalyst and convenient approach for catalyst preparation.

Hydroxylated metal–organic-layer nanocages anchoring single atomic cobalt sites for robust photocatalytic CO_(2) reduction

Assembly of two-dimensional(2D)metal–organic layers(MOLs)based on the hard and soft acid–base theorem represents an exquisite strategy for the construction of photocatalytic platforms in virtue of the highly exposed active sites,much improved mass transport,and greatly elevated stability.Herein,nanocages composed of MOLs are produced for the first time through a cosolvent approach utilizing zirconium-based UiO-66-(OH)2 as the structural precursor.To endow the catalytic activity for CO_(2) conversion,single atomic Co^(2+)sites are appended to the Zr-oxo nodes of the MOL cages,demonstrating a remarkable CO yield of 7.74 mmol·g^(-1)·h^(-1) and operational stability of 97.1%product retention after five repeated cycles.Such an outstanding photocatalytic performance is mainly attributed to the unique nanocage morphology comprising enormous 2D nanosheets for augmented Co^(2+)exposure and the abundant surface hydroxyl groups for local CO_(2) enrichment.This work underlines the tailoring of both metal–organic framework(MOF)morphology and functionality to boost the turnover rate of photocatalytic CO_(2) reduction reaction(CO_(2)RR).

Controlled synthesis of MOF-derived hollow and yolk–shell nanocages for improved water oxidation and selective ethylene glycol reformation

Delicately designed metal–organic framework(MOF)-derived nanostructured electrocatalysts are essential for improving the reaction kinetics of the oxygen evolution reaction and tuning the selectivity of small organic molecule oxidation reactions.Herein,novel oxalate-modified hollow CoFe-based layered double hydroxide nanocages(h-CoFe-LDH NCs)and yolk–shell ZIF@CoFe-LDH nanocages(ys-ZIF@CoFe-LDH NCs)are developed through an etching–doping reconstruction strategy from a Co-based MOF precursor(ZIF-67).The distinctive nanostructures,along with the incorporation of the secondary metal element and intercalated oxalate groups,enable h-CoFe-LDH NCs and ys-ZIF@CoFe-LDH NCs to expose more active sites with high intrinsic activity.The resultant h-CoFe-LDH NCs exhibit outstanding OER activity with an overpotential of only 278 mV to deliver a current density of 50 mA cm^(-2).Additionally,controlling the reconstruction degree enables the formation of ys-ZIF@CoFe-LDH NCs with a yolk–shell nanocage nanostructure,which show outstanding electrocatalytic performance for the selective ethylene glycol oxidation reaction(EGOR)toward formate,with a Faradaic efficiency of up to 91%.Consequently,a hybrid water electrolysis system integrating the EGOR and the hydrogen evolution reaction using Pt/C||ys-ZIF@CoFe-LDH NCs is explored for energy-saving hydrogen production,requiring a cell voltage 127 mV lower than water electrolysis to achieve a current density of 50 mA cm^(-2).This work demonstrates a feasible way to design advanced MOF-derived electrocatalysts toward enhanced electrocatalytic reactions.

Prussian blue analogues-derived nitrogen-doped carboncoated FeO/CoO hollow nanocages as a high-performance anode material for Li storage

The design of electrode materials with specific structures is considered a promising approach for improving the performance of lithium-ion batteries(LIBs).In this paper,FeO/CoO hollow nanocages coated with a N-doped carbon layer(FCO@NC)was prepared using Fe-Co-based Prussian blue analogs(PBA)as a precursor.During the synthesis,dopamine was the carbon and nitrogen source.The reducing atmosphere was assured via NH_3/Ar,which regulated the vacancies in the structure of FCO@NC as well as increased its conductivity.When used as anode materials for LIBs,the FCO@NC nanocages deliver a high reversible capacity of 774.89 mAh·g^(-1)at 0.3 A·g^(-1)after200 cycles with a capacity retention rate of 80.4%and426.76 mAh·g^(-1)after 500 cycles at a high current density of 1 A·g^(-1).It is demonstrated that the hollow nanocage structure can effectively enhance the cycle stability,and the heat treatment in NH_(3)/Ar atmosphere contributes to the oxygen vacancy content of the electrode materials,further facilitating its conductivity and electrochemical performance.

Radical organometallic nanocages with redox switchable poly-NHC ligands

Developing discrete radical organometallic nanocages is essential for fabricating functional materials.In this study,we construct a series of poly-NHC-based(NHC=N-heterocyclic carbene)organometallic nanocages 3a-3c with different sizes by employing redox-active bis(triarylamine)derivatives with differentπ-conjugated spacers as building blocks.The varied sizes of nanocages 3a-3c modulate the distance of the redox-active centers and reversibly convert them to radical nanocages 3a^(2+)-3c^(2+)through chemical and electrochemical oxidation.Radical nanocages 3a^(2+)-3c^(2+)display clear bond and angle alteration and retention of their three-dimensional topologies.This work not only merely proves that these nanocages are excellent stimulus-responsive materials but also opens a door to the rational design of novel radical organometallic nanocages.

Post-modification of MOF to fabricate single-atom dispersed hollow nanocages catalysts for enhancing CO_(2)conversion

During the catalytic process,the microenvironment and surface area of the catalyst will affect the catalytic performance.Hence,an assisted organic linker coated metal-organic framework(MOF)has been applied,to form Ni/HNC(HNC represents hollow nanocage)for electrocatalytic CO_(2)reduction.Remarkably,Ni/HNC achieves superb activity with high Faradaic efficiency(FE)of 97.2%at 0.7 V vs.reversible hydrogen electrode(RHE)towards CO_(2)conversion to CO.In contrast to Ni/NPC(afforded from the naked MOF),the Ni/HNC displays higher FE and selectivity on CO rather than H_(2),owing to the large nanocage which extraordinarily facilitates CO_(2)enrichment and the active sites easily accessible.This work provides a general and feasible route to construct high-efficient electrochemical CO_(2)reduction reaction(EC-CO_(2)RR)catalysts via post-modified MOFs.

Highly active and stable Cu_(9)S_(5)-MoS_(2)heterostructures nanocages enabled by dual-functional Cu electrocatalyst with enhanced potassium storage

The intrinsic poor electrical conductivity,severe dissolution of K x S y intermediates,and inferior conversion reaction reversibility extremely impede the practical application of the transition-metal chalcogenides(TMDs)anode for potassium-ion batteries(PIBs).Herein,a rationally designed Cu_(9)S_(5)/MoS_(2)/C heterostruc-ture hollow nanocage was synthesized with assistance from metal-organic frameworks(MOFs)precursor.During the K-storage process,the homogeneously distributed the sulfiphilic nature of Cu 0 reaction prod-uct could act as a dual-functional catalyst,not only facilitating the rapid charge transfer but also effec-tively anchoring(K x S y)polysulfides,thus boosting K-storage reactions reversibility during the conversion reaction process.When applied as an anode for PIBs,the as-prepared heterostructure exhibits excellent reversible capacity and long cycle lifespan(350.5 mAh g^(-1)at 0.1 A g^(-1)and 0.04%per cycle capacity de-cay at 1 A g^(-1)after 1000 cycles).Additionally,the potassium storage mechanism is distinctly revealed by in-situ characterizations.The nanoarchitecture designing strategy for the advanced electrode in this work could provide vital guidance for relevant energy storage materials.

Ultra-fast microwave aided synthesis of gold nanocages and structural maneuver studies

Gold nanocages （AuNcgs） are well-studied, hollow, metallic nanostructures that have fascinated researchers in the fields of nanotechnology, materials science, photoelectronics, biotechnology, and medical science for the last decade. However, the time-consuming synthesis of AuNcgs has limited their widespread use in materials science and nano-biotechnology. A novel, ultra-fast, simple, and highly convenient method for the production of AuNcgs using microwave heating is demonstrated herein. This quick method of AuNcg synthesis requires mild laboratory conditions for large-scale production of AuNcgs. The microwave heating technique offers the advantage of precise mechanical control over the temperature and heating power, even for the shortest reaction period （i.e., seconds）. Microwave-synthesized AuNcgs were compared with conventionally synthesized AuNcgs. Structural maneuver studies employing the conventionally produced AuNcgs revealed the formation of screw dislocations and a shift in the lattice plane. Detailed characterization of the microwave-generated AuNcgs was performed using high resolution transmission electron microscopy （HRTEM）, scanning electron microscopy （SEM）, X-ray powder diffraction （XRD）, and spectroscopic techniques.

Advanced Ni-Nx-C single-site catalysts for CO2 electroreduction to CO based on hierarchical carbon nanocages and S-doping

Metal-nitrogen-carbon materials are promising catalysts for CO2 electroreduction to CO. Herein, by taking the unique hierarchical carbon nanocages as the support, an advanced nickel-nitrogen-carbon single-site catalyst is conveniently prepared by pyrolyzing the mixture of NiCl2 and phenanthroline, which exhibits a Faradaic efficiency plateau of > 87% in a wide potential window of −0.6 – −1.0 V. Further S-doping by adding KSCN into the precursor much enhances the CO specific current density by 68%, up to 37.5 A·g−1 at −0.8 V, along with an improved CO Faradaic efficiency plateau of > 90%. Such an enhancement can be ascribed to the facilitated CO pathway and suppressed hydrogen evolution from thermodynamic viewpoint as well as the increased electroactive surface area and improved charge transfer fromkinetic viewpoint due to the S-doping. This study demonstrates a simple and effective approach to advanced electrocatalysts by synergetic modification of the porous carbon-based support and electronic structure of the active sites.

N-doped carbon nanocages： Bifunctional electrocatalysts for the oxygen reduction and evolution reactions

Highly effident metal-free, carbon-based, bi-functional electrocatalysts for the oxygen evolution reaction （OER） and oxygen reduction reaction （ORR） have attracted increased attention for use in electrochemical energy conversion systems, owing to their low cost and high activity. In this work, N-doped carbon nanocages （N-CCs） with a porous self-supported architecture and high specific surface area are synthesized by a facile interfacial assembly synthetic route. The materials are comprehensively characterized by scanning electron microscop36 transmission electron microscopy, nitrogen adsorption-desorption experiments, X-ray diffraction, and X-ray photoelectron spectroscopy. Cyclic voltammetry , chronoamperometry, and linear sweep voltammetry demonstrate that the as-prepared N-CC could serve as an effective metal-free electrocatalyst with excellent catalytic activity, long-term operation durability, and excellent methanol tolerance for the ORR in alkaline media. In the presence of 3 mM methanol, the half wave potential of the N-CCs for the ORR is 190 mV; this is more positive than that of the commercial Pt/C electrocatalyst. Meanwhile, the N-CCs also show an OER activity comparable to that of the commercial Ru/C electrocatalyst, revealing their bifunctional property.