Ultrathin‐Nanosheet‐Induced Synthesis of 3D Transition Metal Oxides Networks for Lithium Ion Battery Anodes

A general ultrathin‐nanosheet‐induced strategy for producing a 3D mesoporous network of Co₃O₄ is reported. The fabrication process introduces a 3D N‐doped carbon network to adsorb metal cobalt ions via dipping process. Then, this carbon matrix serves as the sacrificed template, whose N‐doping effect and ultrathin nanosheet features play critical roles for controlling the formation of Co₃O₄ networks. The obtained material exhibits a 3D interconnected architecture with large specific surface area and abundant mesopores, which is constructed by nanoparticles. Merited by the optimized structure in three length scales of nanoparticles–mesopores–networks, this Co₃O₄ nanostructure possesses superior performance as a LIB anode: high capacity (1033 mAh g^?1 at 0.1 A g^?1) and long‐life stability (700 cycles at 5 A g^?1). Moreover, this strategy is verified to be effective for producing other transition metal oxides, including Fe₂O₃, ZnO, Mn₃O₄, NiCo₂O₄, and CoFe₂O₄.     

MoSe2‐Covered N,P‐Doped Carbon Nanosheets as a Long‐Life and High‐Rate Anode Material for Sodium‐Ion Batteries

MoSe₂ grown on N,P‐co‐doped carbon nanosheets is synthesized by a solvothermal reaction followed with a high‐temperature calcination. This composite has an interlayer spacing of MoSe₂ expanded to facilitate sodium‐ion diffusion, MoSe₂ immobilized on carbon nanosheets to improve charge‐transfer kinetics, and N and P incorporated into carbon to enhance its interaction with active species upon cycling. These features greatly improve the electrochemical performance of this composite, as compared to all the controls. It presents a specific capacity of 378 mAh g^?1 after 1000 cycles at 0.5 A g^?1, corresponding to 87% of the capacity at the second cycle. Ex situ Raman spectra and high‐resolution transmission electron microscopy images confirm that it is element Se, rather than MoSe₂, formed after the charging process. The interaction of the active species with modified carbon is simulated using density functional theory to explain this excellent stability. The superior rate capability, where the capacity at 15 A g^?1 equals ≈55% of that at 0.5 A g^?1, could be associated with the significant contribution of pseudocapacitance. By pairing with homemade Na₃V₂(PO₄)₃/C, this composite also exhibits excellent performances in full cells.     

B‐doped Carbon Coating Improves the Electrochemical Performance of Electrode Materials for Li‐ion Batteries

An evolutionary modification approach, boron doped carbon coating, is initially used to improve the electrochemical properties of electrode materials of lithium‐ion batteries, such as Li₃V₂(PO₄)₃, and demonstrates apparent and significant modification effects. Based on the precise analysis of X‐ray photoemission spectroscopy results, Raman spectra, and electrochemical impedance spectroscopy results for various B‐doped carbon coated Li₃V₂(PO₄)₃ samples, it is found that, among various B‐doping types (B₄C, BC₃, BC₂O and BCO₂), the graphite‐like BC₃ dopant species plays a huge role on improving the electronic conductivity and electrochemical activity of the carbon coated layer on Li₃V₂(PO₄)₃ surface. As a result, when compared with the bare carbon coated Li₃V₂(PO₄)₃, the electrochemical performances of the B‐doped carbon coated Li₃V₂(PO₄)₃ electrode with a moderate doping amount are greatly improved. For example, when cycled under 1 C and 20 C in the potential range of 3.0–4.3 V, this sample shows an initial capacity of 122.5 and 118.4 mAh g^?1, respectively; after 200 cycles, nearly 100% of the initial capacity is retained. Moreover, the modification effects of B‐doped carbon coating approach are further validated on Li₄Ti₅O₁₂ anode material.     

Embedding RhPx in N,P Co‐Doped Carbon Nanoshells Through Synergetic Phosphorization and Pyrolysis for Efficient Hydrogen Evolution

Rational design and controllable synthesis of well‐defined nanostructures with high stability and Pt‐like activity for hydrogen evolution reaction (HER) are critical for renewable energy conversion. Herein, a unique pyrolysis strategy is demonstrated for the synthesis of RhP_x nanoparticles (NPs) in N, P co‐doped thin carbon nanoshells (RhP_x@NPC nanoshells) that display high electrocatalytic activity and stability over a wide pH range. This strategy involves simultaneous phosphorization and pyrolysis processes that can produce highly‐dispersed RhP_x NPs within N, P co‐doped carbon nanoshells and at the same time induce thinning of carbon nanoshells from inside out. The resulting RhP_x@NPC nanoshells not only possess Pt‐like activity for HER with low overpotentials to achieve 10 mA cm^?2 (22 mV in 0.5 m H₂SO₄, 69 mV in 1.0 m KOH, and 38 mV in 1.0 m phosphate buffered saline (PBS)) but also provide long‐term durability in a wide pH range. The remarkable HER performance of RhP_x@NPC nanoshells is ascribed to the high surface area, abundant mesoporosity, strong catalyst–support interaction, ultrathin carbon encapsulation, and N, P co‐doping. This work provides an effective strategy for designing heterostructured electrocatalysts with high catalytic activity and stability desired for reactions that may occur under harsh conditions.     

Few Layered N,P Dual‐Doped Carbon‐Encapsulated Ultrafine MoP Nanocrystal/MoP Cluster Hybrids on Carbon Cloth: An Ultrahigh Active and Durable 3D Self‐Supported Integrated Electrode for Hydrogen Evolution Reaction in a Wide pH Range

Development of highly active and stable electrocatalysts is a key to realize efficient hydrogen evolution through water electrolysis. Here, the development of a 3D self‐supported integrated electrode constituting few layered N, P dual‐doped carbon‐encapsulated ultrafine MoP nanocrystal/MoP cluster hybrids on carbon cloth (FLNPC@MoP‐NC/MoP‐C/CC) is demonstrated. Benefiting from novel structural features including fully open and accessible nanoporosity, ultrasmall size of MoP‐NCs on MoP‐Cs as well as strong synergistic effects of N, P dual‐doped carbon layers with MoP‐NCs, the FLNPC@MoP‐NC/MoP‐C/CC as a 3D self‐supported binder‐free integrated electrode exhibits extraordinary catalytic activity for the hydrogen evolution reaction (HER) with extremely low overpotentials at all pH values ( j = 10 mA cm^?2 at η = 74, 106, and 69 mV in 0.5 m H₂SO₄, 1.0 m PBS, and 1.0 m KOH electrolytes, respectively). To the best of our knowledge, the ultrahigh electrocatalytic performance represents one of the best MoP‐based HER electrocatalysts reported so far. Additionally, few layered N, P dual‐doped carbon can effectively prevent MoP‐NC/MoP‐C from corrosion, making the FLNPC@MoP‐NC/MoP‐C/CC exhibit nearly unfading stability after 50 h testing in acidic, neutral, and alkaline media, which shows great promise for electrocatalytic water splitting application.     

Defect‐Rich Nitrogen Doped Co3O4/C Porous Nanocubes Enable High‐Efficiency Bifunctional Oxygen Electrocatalysis

Heteroatom doping plays a significant role in optimizing the catalytic performance of electrocatalysts. However, research on heteroatom doped electrocatalysts with abundant defects and well‐defined morphology remain a great challenge. Herein, a class of defect‐engineered nitrogen‐doped Co₃O₄ nanoparticles/nitrogen‐doped carbon framework (N‐Co₃O₄@NC) strongly coupled porous nanocubes, made using a zeolitic imidazolate framework‐67 via a controllable N‐doping strategy, is demonstrated for achieving remarkable oxygen evolution reaction (OER) catalysis. X‐ray photoelectron spectroscopy, X‐ray absorption fine structure, and electron spin resonance results clearly reveal the formation of a considerable amount of nitrogen dopants and oxygen vacancies in N‐Co₃O₄@NC. The defect engineering of N‐Co₃O₄@NC makes it exhibit an overpotential of only 266 mV to reach 10 mA cm^?2, a low Tafel slope of 54.9 mV dec^?1 and superior catalytic stability for OER, which is comparable to that of commercial RuO₂. Density functional theory calculations indicate N‐doping could promote catalytic activity via improving electronic conductivity, accelerating reaction kinetics, and optimizing the adsorption energy for intermediates of OER. Interestingly, N‐Co₃O₄@NC also shows a superior oxygen reduction reaction activity, making it a bifunctional electrocatalyst for zinc–air batteries. The zinc–air battery with the N‐Co₃O₄@NC cathode demonstrates superior efficiency and durability, showing the feasibility of N‐Co₃O₄/NC in electrochemical energy devices.     

Refining Energy Levels in ReS2 Nanosheets by Low‐Valent Transition‐Metal Doping for Dual‐Boosted Electrochemical Ammonia/Hydrogen Production

Electrocatalytic nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) are intriguing approaches to nitrogen fixation and hydrogen production under ambient conditions, given the need to discover efficient and stable catalysts to light up the “green chemistry” future. However, bottlenecks are often found during N₂/H₂O activation, the very first step of NRR/HER, due to energetic electron injection from the surface of electrocatalysts. It is reported that the bottlenecks for both NRR and HER can be tackled by engineering the energy level via low‐valent transition‐metal doping, simultaneously, where rhenium disulfide (ReS₂) is employed as a model platform to prove the concept. The doped low‐valent transition‐metal domains (e.g., Fe, Co, Ni, Cu, Zn) in ReS₂ provide more active sites for N₂/H₂O chemisorption and electron transfer, not only weakening the N?N/O? H bonds for easier dissociation through proton coupling, but also elevating d‐band center toward the Fermi level with more electron energy for N₂/H₂O reduction. As a result, it is found that iron‐doped ReS₂ nanosheets wrapped nitrogen‐doped carbon nanofiber (Fe‐ReS₂@N‐CNF) catalyst exhibits superior electrochemical activity with eightfold higher ammonia production yield of 80.4 µg h^?1 mg^?1_cat., and lower onset overpotential of 146 mV and Tafel slope of 63 mV dec^?1, when comparing with the pristine ReS₂.     

Facile Synthesis of Manganese‐Oxide‐Containing Mesoporous Nitrogen‐Doped Carbon for Efficient Oxygen Reduction

Developing low‐cost non‐precious metal catalysts for high‐performance oxygen reduction reaction (ORR) is highly desirable. Here a facile, in situ template synthesis of a MnO‐containing mesoporous nitrogen‐doped carbon (m‐N‐C) nanocomposite and its high electrocatalytic activity for a four‐electron ORR in alkaline solution are reported. The synthesis of the MnO‐m‐N‐C nanocomposite involves one‐pot hydrothermal synthesis of Mn₃O₄@polyaniline core/shell nanoparticles from a mixture containing aniline, Mn(NO₃)₂, and KMnO₄, followed by heat treatment to produce N‐doped ultrathin graphitic carbon coated MnO hybrids and partial acid leaching of MnO. The as‐prepared MnO‐m‐N‐C composite catalyst exhibits high electrocatalytic activity and dominant four‐electron oxygen reduction pathway in 0.1 M KOH aqueous solution due to the synergetic effect between MnO and m‐N‐C. The pristine MnO shows little electrocatalytic activity and m‐N‐C alone exhibits a dominant two‐electron process for ORR. The MnO‐m‐N‐C composite catalyst also exhibits superior stability and methanol tolerance to a commercial Pt/C catalyst, making the composite a promising cathode catalyst for alkaline methanol fuel cell applications. The synergetic effect between MnO and N‐doped carbon described provides a new route to design advanced catalysts for energy conversion.     

Low‐Cost Chitosan‐Derived N‐Doped Carbons Boost Electrocatalytic Activity of Multiwall Carbon Nanotubes

An effective strategy is proposed to enhance the oxygen reduction reaction (ORR) performance of multiwall carbon nanotubes (MWCNTs) in both acid and alkaline electrolytes by coating them with a layer of biomass derivative N‐doped hydrothermal carbons. The N‐doped amorphous carbon coating plays triple roles: it (i) promotes the assembly of MWCNTs into a 3D network therefore improving the mass transfer and thus increasing the catalytic activity; (ii) protects the Fe‐containing active sites, present on the surface of the MWCNTs, from H₂O₂ poisoning; (iii) creates nitrogenated active sites and hence further enhances ORR activity and robustness.     

General Synthesis of N‐Doped Macroporous Graphene‐Encapsulated Mesoporous Metal Oxides and Their Application as New Anode Materials for Sodium‐Ion Hybrid Supercapacitors

A general method to synthesize mesoporous metal oxide@N‐doped macroporous graphene composite by heat‐treatment of electrostatically co‐assembled amine‐functionalized mesoporous silica/metal oxide composite and graphene oxide, and subsequent silica removal to produce mesoporous metal oxide and N‐doped macroporous graphene simultaneously is reported. Four mesoporous metal oxides (WO_{3? x} , Co₃O₄, Mn₂O₃, and Fe₃O₄) are encapsulated in N‐doped macroporous graphene. Used as an anode material for sodium‐ion hybrid supercapacitors (Na‐HSCs), mesoporous reduced tungsten oxide@N‐doped macroporous graphene (m‐WO_{3? x} @NM‐rGO) gives outstanding rate capability and stable cycle life. Ex situ analyses suggest that the electrochemical reaction mechanism of m‐WO_{3? x} @NM‐rGO is based on Na⁺ intercalation/de‐intercalation. To the best of knowledge, this is the first report on Na⁺ intercalation/de‐intercalation properties of WO_{3? x} and its application to Na‐HSCs.     

Efficient Synthesis of Heteroatom (N or S)‐Doped Graphene Based on Ultrathin Graphene Oxide‐Porous Silica Sheets for Oxygen Reduction Reactions

Heteroatom (N or S)‐doped graphene with high surface area is successfully synthesized via thermal reaction between graphene oxide and guest gases (NH₃ or H₂S) on the basis of ultrathin graphene oxide‐porous silica sheets at high temperatures. It is found that both N and S‐doping can occur at annealing temperatures from 500 to 1000 °C to form the different binding configurations at the edges or on the planes of the graphene, such as pyridinic‐N, pyrrolic‐N, and graphitic‐N for N‐doped graphene, thiophene‐like S, and oxidized S for S‐doped graphene. Moreover, the resulting N and S‐doped graphene sheets exhibit good electrocatalytic activity, long durability, and high selectivity when they are employed as metal‐free catalysts for oxygen reduction reactions. This approach may provide an efficient platform for the synthesis of a series of heteroatom‐doped graphenes for different applications.     

High‐Performance Wearable Micro‐Supercapacitors Based on Microfluidic‐Directed Nitrogen‐Doped Graphene Fiber Electrodes

Fiber‐shaped micro‐supercapacitors (micro‐SCs) have attracted enormous interest in wearable electronics due to high flexibility and weavability. However, they usually present a low energy density because of inhomogeneity and less pores. Here, we demonstrate a microfluidic‐directed strategy to synthesize homogeneous nitrogen‐doped porous graphene fibers. The porous fibers‐based micro‐SCs utilize solid‐state phosphoric acid/polyvinyl alcohol (H₃PO₄/PVA) and 1‐ethyl‐3‐methylimidazolium tetrafluoroborate/poly(vinylidenefluoride‐co‐hexafluoropropylene) (EMIBF₄/PVDF‐HFP) electrolytes, which show significant improvements in electrochemical performances. Ultralarge capacitance (1132 mF cm^?2), high cycling‐stability, and long‐term bending‐durability are achieved based on H₃PO₄/PVA. Additionally, high energy densities of 95.7–46.9 µWh cm^?2 at power densities of 1.5–15 W cm^?2 are obtained in EMIBF₄/PVDF‐HFP. The key to higher performances stems from microfluidic‐controlled fibers with a uniformly porous network, large specific surface area (388.6 m² g^?1), optimal pyridinic nitrogen (2.44%), and high electric conductivity (30785 S m^?1) for faster ion diffusion and flooding accommodation. By taking advantage of these remarkable merits, this study integrates micro‐SCs into flexible and fabric substrates to power audio–visual electronics. The main aim is to clarify the important role of microfluidic techniques toward the architecture of electrodes and promote development of wearable electronics.     

Nitrogen‐Doped Cobalt Oxide Nanostructures Derived from Cobalt–Alanine Complexes for High‐Performance Oxygen Evolution Reactions

Taking advantage of the self‐assembling function of amino acids, cobalt–alanine complexes are synthesized by straightforward process of chemical precipitation. Through a controllable calcination of the cobalt–alanine complexes, N‐doped Co₃O₄ nanostructures (N‐Co₃O₄) and N‐doped CoO composites with amorphous carbon (N‐CoO/C) are obtained. These N‐doped cobalt oxide materials with novel porous nanostructures and minimal oxygen vacancies show a high and stable activity for the oxygen evolution reaction. Moreover, the influence of calcination temperature, electrolyte concentration, and electrode substrate to the reaction are compared and analyzed. The results of experiments and density functional theory calculations demonstrate that N‐doping promotes the catalytic activity through improving electronic conductivity, increasing OH^? adsorption strength, and accelerating reaction kinetics. Using a simple synthetic strategy, N‐Co₃O₄ reserves the structural advantages of micro/nanostructured complexes, showing exciting potential as a catalyst for the oxygen evolution reaction with good stability.     

FeP Quantum Dots Confined in Carbon‐Nanotube‐Grafted P‐Doped Carbon Octahedra for High‐Rate Sodium Storage and Full‐Cell Applications

Transition metal phosphides (TMPs) possess high theoretical sodium storage capacities, but suffer from poor rate performance, due to their intrinsic low conductivity and large volume expansion upon sodiation/desodiation. Compositing TMPs with carbon materials or downsizing their feature size are recognized as efficient approaches to address the above issues. Nevertheless the surface‐controlled capacitive behavior is generally dominated, which inevitably compromises the charge/discharge platform, and decreases the operational potential window in full‐cell constructions. In this work, a novel architecture (FeP@OCF) with FeP quantum dots confined in P‐doped 3D octahedral carbon framework/carbon nanotube is rationally designed. Such structure enables a simultaneous enhancement on the diffusion‐controlled capacity in the platform region (2.3 folds), and the surface‐controlled capacity in the slope region (2.9 folds) as compared to that of pure FeP. As a result, an excellent reversible capacity (674 mAh g^?1@ 0.1 A g^?1) and a record high‐rate performance (262 mAh g^?1 @ 20 A g^?1) are achieved. A full‐cell FeP@OCF// Na₃V₂(PO₄)₃ is also constructed showing an outstandingly high energy density of 185 Wh kg^?1 (based on the total mass of active materials in both electrodes), which outperforms the state‐of‐the art TMP‐based sodium‐ion battery full cells.     

Ru–Ru2PΦNPC and NPC@RuO2 Synthesized via Environment‐Friendly and Solid‐Phase Phosphating Process by Saccharomycetes as N/P Sources and Carbon Template for Overall Water Splitting in Acid Electrolyte

Although numerous ruthenium‐based phosphates possess high catalytic activities for hydrogen evolution reaction (HER), most of them rely on dangerous and toxic synthesis routes. Biological slices confirm that Ru ions can penetrate the cell walls of saccharomycete, which facilitates the adsorption of Ru ions. Herein, based on a green synthesis process by saccharomycete cells as the carbon template and nitrogen/phosphorus (N/P) sources, novel Janus‐like ruthenium–ruthenium phosphide nanoparticles embedded into a N/P dual‐doped carbon matrix (Ru–Ru₂PΦNPC) electrocatalyst for HER are synthesized. Electrochemical tests reveal that Ru–Ru₂PΦNPC displays remarkable performance with a low overpotential of 42 mV at 10 mA cm^?2 and demonstrates superior stability at a high current density in 0.5 m H₂SO₄. Furthermore, ruthenium oxide nanoparticles coated N/P dual‐doped carbon (NPC@RuO₂) are also synthesized with a yolk–shell structure using saccharomycete cells as the core template and RuO₂ as a shell to isolate saccharomycete cells from the oxidation reaction during calcination in air. The NPC@RuO₂ as oxygen evolution reaction electrocatalyst possesses a low overpotential of 220 mV at 10 mA cm^?2. Finally, the Ru–Ru₂PΦNPC is integrated as a cathode and NPC@RuO₂ is integrated as an anode to construct a two‐electrode electrolyzer to enable an excellent performance for overall water splitting with a cell voltage of 1.50 V at 10 mA cm^?2 in 0.5 m H₂SO₄.     

Identifying Active Sites of Nitrogen‐Doped Carbon Materials for the CO2 Reduction Reaction

Nitrogen‐doped carbon materials are proposed as promising electrocatalysts for the carbon dioxide reduction reaction (CRR), which is essential for renewable energy conversion and environmental remediation. Unfortunately, the unclear cognition on the CRR active site (or sites) hinders further development of high‐performance electrocatalysts. Herein, a series of 3D nitrogen‐doped graphene nanoribbon networks (N‐GRW) with tunable nitrogen dopants are designed to unravel the site‐dependent CRR activity/selectivity. The N‐GRW catalyst exhibits superior CO₂ electrochemical reduction activity, reaching a specific current of 15.4 A g_catalyst^?1 with CO Faradaic efficiency of 87.6% at a mild overpotential of 0.49 V. Based on X‐ray photoelectron spectroscopy measurements, it is experimentally demonstrated that the pyridinic N site in N‐GRW serves as the active site for CRR. In addition, the Gibbs free energy calculated by density functional theory further illustrates the pyridinic N as a more favorable site for the CO₂ adsorption, *COOH formation, and *CO removal in CO₂ reduction.     

Phosphate‐Mediated Immobilization of High‐Performance AuPd Nanoparticles for Dehydrogenation of Formic Acid at Room Temperature

Dehydrogenation of formic acid (FA) is a promising alternative to fossil fuels, to provide clean energy for the future energy economy. The synthesis of highly active catalysts for FA dehydrogenation at room temperature has attracted a lot of attention. Herein, for the first time, highly active aurum–palladium nanoparticles (AuPd NPs) immobilized on nitrogen (N)‐doped porous carbon are fabricated through a phosphate‐mediation approach. The N‐doped carbon anchored with phosphate, which can be removed in alkaline solution during the reduction process of metal ions, shows an enhanced performance of absorbing and dispersion of both Au and Pd ions, which is a key to the synthesis of highly dispersed ultrafine AuPd NPs. The as‐prepared catalyst (designated as Au₂Pd₃@(P)N‐C) exhibits an extraordinarily high turnover frequency of 5400 h^?1 and a 100% H₂ selectivity for FA dehydrogenation at 30 °C. This phosphate‐mediation approach provides a new way to fabricate highly active metal NPs for catalytic application, pushing heterogeneous catalysts forward for practical usage in energy storage and conversion.     

Blood Ties: Co3O4 Decorated Blood Derived Carbon as a Superior Bifunctional Electrocatalyst

A simple, versatile and cheap synthetic route is demonstrated for the preparation of Co₃O₄ decorated blood powder derived heteroatom doped porous carbon (BDHC). The inorganic hybrid performs well as an advanced bifunctional non‐precious metal electrocatalyst. The hybridization of Co₃O₄ with the blood‐derived carbon results in improved activities not only towards the oxygen reduction reaction (ORR), but also in the reverse oxygen evolution reaction (OER). An improved ORR activity and a tuned four electron transfer selectivity can be assigned to a synergistic catalytic effect due the intimate contact between Co₃O­₄ particles and the highly conductive heteroatom doped carbon support, mediated by cobalt‐nitrogen or cobalt‐phosphorous coordination sites. This heterojunction may facilitate the electron transfer by preventing an accumulation of electron density within the Co₃O­₄ particles. The straight‐forward and cheap synthesis of the highly active and durable electrocatalyst make it a promising candidate for a next‐generation bifunctional electrocatalyst for applications such as reversible fuel cells/electrolyzers or metal air batteries.     

Microporosity‐Controlled Synthesis of Heteroatom Codoped Carbon Nanocages by Wrap‐Bake‐Sublime Approach for Flexible All‐Solid‐State‐Supercapacitors

Heteroatom‐doped carbon nanomaterials with high surface area and tunable microporosity are important but they generally require difficult and multistep syntheses. Herein, a simple and straightforward strategy is introduced that involves a wrap‐bake‐sublime approach to synthesize microporosity controlled and heteroatom codoped carbon nanocages. A zinc‐containing zeolitic imidazolate framework (ZIF‐8) core is wrapped in a cross‐linked oligomer containing nitrogen and phosphorus, oligo(cyclotriphosphazene‐co‐hexahydroxytriphenylene) (OCHT). As‐synthesized core–shell ZIF‐8‐OCHT nanoparticles are baked at high temperatures to sublimate zinc through OCHT shell, resulting in a porous structure. Meanwhile, hollow cavities are introduced into N,P codoped carbon nanocages (NPCNs) via the sacrificial nature of ZIF‐8 template. The microporosity is finely tuned by controlling thickness of the OCHT shell during synthesis of the core–shell nanoparticles, since the sublimation tendency of zinc component at high temperatures depends on the thickness of OCHT shell. A systematic correlation between the electrochemical performance of NPCNs and their microporosity is confirmed. Furthermore, the electrochemical performance of the NPCNs is related to the degree of heteroatom codoping. The approach is successfully scaled‐up without compromising their electrochemical performance. Finally, a symmetric and flexible all‐solid‐state‐supercapacitor with high energy and power density, and a long‐term cycleability is demonstrated (75% capacitance retention after 20 000 cycles).     

Nitrogen‐Doped Single‐Walled Carbon Nanotubes Grown on Substrates: Evidence for Framework Doping and Their Enhanced Properties

Nitrogen‐doped single‐walled carbon nanotubes (SWCNTs) are synthesized directly on silicon and quartz substrates through a normal chemical vapor deposition (CVD) method. Thermogravimetry mass spectrometry measurements and Raman spectroscopy give firm evidence for framework nitrogen doping. X‐ray‐photoelectron‐spectroscopy analysis further obtains the bonding style of the nitrogen atoms in the carbon framework. The nitrogen doping significantly changes the properties of the SWCNTs. All of the tubes behave like metallic tubes in field‐effect transistors. The doped nitrogen atoms introduce a stronger affinity for the SWCNTs to metal nanoparticles. Compared with pristine SWCNTs, the nitrogen‐doped tubes show enhanced sensitivity and selectivity for electrochemical detection of some electrophilic species including O₂, H₂O₂, and Fe³⁺. They also present improved electrocatalytic activity for oxygen reduction. These unique properties of the nitrogen‐doped SWCNTs endow them with important potential applications in various fields.