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Changing the composition is an important way to regulate the electrocatalytic performance of the oxygen evolution reaction (OER) for metallic compounds. Clarifying the synergistic mechanism among different compositions is a key scientific problem to be solved urgently. Here, based on first-principles calculations, a Ni–O–Fe multisite dynamic synergistic reaction mechanism (MDSM) for the OER of Fe-doped NiOOH (NiFeOOH) has been discovered. Based on the MDSM, Fe/O/Ni are triggered as the active sites in turn, resulting in an overpotential of 0.33 V. The factors affecting the deprotonation, O–O coupling, and O2 desorption during the OER process are analyzed. The electron channels related to the magnetic states among Fe–O–Ni is revealed, which results in the decoupling between OER sites and the oxidation reaction sites. O–O coupling and O2 desorption are affected by ferromagnetic coupling and the instability of the lattice O during the OER process, respectively. The results give a comprehensive understanding of the active sites in NiFeOOH and provide a new perspective on the synergistic effects among different compositions in metal compounds during the OER process. [ABSTRACT FROM AUTHOR]

To support the global goal of carbon neutrality, numerous efforts have been devoted to the advancement of electrochemical energy conversion (EEC) and electrochemical energy storage (EES) technologies. For these technologies, transition metal dichalcogenide/carbon (TMDC/C) heterostructures have emerged as promising candidates for both electrode materials and electrocatalysts over the past decade, due to their complementary advantages. It is worth noting that interfacial properties play a crucial role in establishing the overall electrochemical characteristics of TMDC/C heterostructures. However, despite the significant scientific contribution in this area, a systematic understanding of TMDC/C heterostructures' interfacial engineering is currently lacking. This literature review aims to focus on three types of interfacial engineering, namely interfacial orientation engineering, interfacial stacking engineering, and interfacial doping engineering, of TMDC/C heterostructures for their potential applications in EES and EEC devices. To accomplish this goal, a combination of experimental and theoretical approaches was used to allow the analysis and summary of the fundamental electrochemical properties and preparation strategies of TMDC/C heterostructures. Moreover, this review highlights the design and utilization of the interfacial engineering of TMDC/C heterostructures for specific EES and EEC devices. Finally, the challenges and opportunities of using interfacial engineering of TMDC/C heterostructures in practical EES and EEC devices are outlined. We expect that this review will effectively guide readers in their understanding, design, and application of interfacial engineering of TMDC/C heterostructures. [ABSTRACT FROM AUTHOR]

The safety, adaptability, and eco-friendliness of zinc-ion batteries have recently been drawing increased attention. However, zinc-ion batteries suffer from irregular interfacial kinetics and uncontrolled Zn2+ deposition. Herein, a novel localized gelation separator (LGS) with low-cost natural cellulose separators has been developed, prepared via a green chemistry process. The LGS can "intelligently" select the deposition site through the updated separator/anode interface due to the repulsion between non-gelation regions and anodes. The solvation shell of ZnSO4 is altered due to the involvement of cellulose, as confirmed by X-ray diffraction patterns, Raman spectra and ab initio molecular dynamics calculations, where the interfacial transfer of Zn2+ is regulated and the activity of water is reduced. A novel linearly increasing polarization was observed using electrochemical impedance spectroscopy, revealing smooth interface kinetics and charge-transfer impedance. With those benefits, the zinc symmetric cell shows stable cyclability for more than 1200 h even at 20 mA cm−2. Superior dendrite suppression was observed using in situ optical microscopy at 20 mA h cm−2. After 300 cycles, the discharge-specific capacity of the MnO2 cell with the LGS was 80 mA h g−1. The LGS also showed excellent performance at −20 °C. This LG strategy has broad prospects and provides new ideas for dendrite-free zinc-ion batteries. [ABSTRACT FROM AUTHOR]

A palladium-promoted oxidative annulation reaction for the synthesis of structurally diverse naphthoquinone-containing heterocycles has been developed, providing switchable access to 1,2-naphthofuroquinones and densely functionalized cyclobutene-fused 1,4-naphthofuroquinones by selective enol/enolate-directed processes. The synthetic application was extended by late-stage functionalization of an anti-HIV drug. The practical value of 1,2-naphthofuroquinone synthesis was highlighted in endothelial protective lead compound development. [ABSTRACT FROM AUTHOR]

Developing highly efficient and low-cost bifunctional electrocatalysts towards the oxygen reduction reaction (ORR) is important for Zn–air batteries (ZABs) but still a challenge. In this work, electronic reconfiguration and structural optimization are simultaneously conducted to enhance the oxygen reduction reaction (ORR) electrocatalytic activity of Co2P nanoparticles, which were doped with Cu and confined within 2D ultrathin N,P-codoped carbon (NPC) nanosheets. Density functional theory calculations reveal that Cu doping can lead to more positive sites at the neighbouring Co site and weaken the binding force between the surface active sites and the adsorbed intermediates, while the 2D ultrathin nanosheets with Cu doped Co2P nanoparticles tightly anchored can remarkably boost the surface exposure of actives sites endowing such an architecture with efficient mass and charge transport pathways. As expected, the optimized Cu doped Co2P on 2D ultrathin N,P-codoped carbon (Cu-Co2P@2D-NPC) with 7.1% Cu doping exhibits a higher half-wave potential of 0.835 V than Pt/C (0.830 V). Meanwhile, flexible solid state ZABs assembled based on the 7.1%Cu-Co2P@2D-NPC hybrid deliver a high power density of 52.5 mW cm−2 and 32 h stability in the flat and folded states. This promising work holds significant potential to fabricate an efficient electrocatalyst for flexible solid state ZABs and further understand the relationship between the structure and activity. [ABSTRACT FROM AUTHOR]

Lithium metal anodes have attracted considerable attention due to their high specific capacity (3860 mA h g−1). However, the volume change and the lithium dendritic growth of Li metal anodes impede their practical application. Researchers have improved the performance of lithium metal anodes by loading lithiophilic materials on 3D current collectors as lithium hosts. Nevertheless, the lithiophilic materials without spatial confinement may undergo severe volume and location changes during the cycling, leading to inhomogeneous lithium deposition, decayed structural stability and electrochemical performance. Herein, lithiophilic ZnO nanoparticle confined 3D porous carbon composite microspheres (3D ZnO@PCCMs) as hosts for lithium metal anodes were developed through a facile and scalable in situ strategy to mitigate the above formidable problems. The microsphere consists of several tens of interconnected empty carbon nanoboxes with ultra-small ZnO nanocrystals embedded in-plane. In the constructed architecture, the ZnO nanoparticles confined within ultrathin carbon walls can effectively prevent the ZnO from agglomerating and detaching from the current collectors during the cycling, inducing the uniform distribution and structural stability of ZnO for guiding the long-term homogenous lithium deposition, while the abundant interconnected empty boxes can sustain massive lithium deposition and accommodate the volume expansion of lithium during cycling. As a result, the as-obtained electrode with ZnO@PCCMs as a 3D host can achieve a very high coulombic efficiency, durability and stability even at high current density and areal capacity. This work delivers a novel concept that stabilizing the lithiophilic seeds can lead to a more stable and excellent cycling performance for lithium metal anodes, and meanwhile provides a low-cost and industrialized manufacturing approach for high-safety and high-performance lithium metal anodes. [ABSTRACT FROM AUTHOR]

Engineering of carbonous materials with excellent electrochemical performances for both sodium and potassium ion batteries is still challenging. In this work, N-doped interconnected carbon spheres with ultrathin nanosheets and expanded interplanar spacing (UNCns) were fabricated by a simple and scalable template-assisted spray pyrolysis method. The hybrid ion storage mechanism endows the UNCns with excellent rate performance and ultra-long cycling lifespan. Moreover, it has been found that the difference between sodium and potassium storage mechanisms in the UNCns strongly influences their performance, which is inspiring to further improve the electrochemical performance of electrode materials by coordinating adsorption (capacitive-controlled) energy storage and redox (diffusion-controlled) energy storage through controlling structural construction. [ABSTRACT FROM AUTHOR]

Hollow β-Mo2C/N-doped carbon composite nanospheres constructed by mesoporous ultrathin carbon nanosheets anchored with ultrasmall β-Mo2C nanoparticles were synthesized through a facile green process. Nanobubbles generated by ethanol–water exchange were utilized as templates for the core, while the precipitates in the solution were directly adopted as the emulsion stabilizer and the shell. Upon the self-polymerization of dopamine, a robust shell consisting of the Mo–polydopamine complex was formed. The size of the as-obtained hollow Mo–polydopamine nanospheres can be tuned by varying the type of gas, which is proportional to the supersaturation of gas. These precursors of hollow Mo–polydopamine nanospheres were then converted into hollow β-Mo2C/N-doped carbon composite nanospheres by high-temperature carbonization treatment. The N-doped carbon matrix can act as an electron conductor and facilitate the prevention of the migration and aggregation of the Mo2C nanoparticles, while the ultrafine Mo2C nanoparticles can achieve maximum material utilization for hydrogen evolution electrocatalysis. In addition, the mesoporous 2D nanosheets combined with their constructed 3D hollow structures can expose numerous active catalytic sites while enabling free diffusion of the electrolyte and mass transfer. As a result, the hollow β-Mo2C/N-doped carbon composite nanospheres exhibit low overpotentials and robust cycling stability in both acidic and alkaline electrolytes. [ABSTRACT FROM AUTHOR]

A graphene-reinforced N-doping porous carbon network is fabricated using a simple strategy for the electrodes of supercapacitors and lithium ion batteries. In this approach, sodium carbonate is dissolved with glucose and urea and then the obtained solution is coated on a metal substrate. A subsequent heating process enables the organic complex to convert into N-doping porous carbon network replicating the pattern of the salt template. Moreover, wave-like graphene is formed at the interspace between the metal and salt, which not only increases the overall electronic conductivity but also enhances structural stability for engaging the material with a free-standing feature. The heterogeneous space-confined effect of metal/salt plays a critical role in the formation of this hybrid, which is further investigated by molecular simulation. The various advantages of 2D and 3D structures endow this carbon hybrid with superior electrochemical properties; as a Li-ion battery anode, the hybrid exhibits high reversible capacity (775 mA h g−1 at 0.1 A g−1) and long cycling stability (stability is maintained after 1000 cycles at 2 A g−1); in supercapacitors, it presents high capacitive property (238 F g−1 at 1 A g−1) and, as a result, it exhibits outstanding capacitance retention (118 F g−1 at 200 A g−1). [ABSTRACT FROM AUTHOR]

Interconnected 3D graphene foams with a large number of controllable micro–mesoporous structures are promising electrode materials for supercapacitors due to their high electrical conductivity and large effective surface area. Here we successfully obtained a flexible high-quality nitrogen and oxygen co-doped 3D nanoporous duct-like graphene@carbon nano-cage film by chemical vapor deposition using nanoporous copper (NPC) as the substrate and further modifying with HNO3. The bicontinuous mesoporous architecture catalyzed by NPC retains the 2D coherent electronic properties of graphene. Carbon nano-cages grown on the surface of the 3D nanoporous graphene combined with the microporous structure caused by heteroatom-doping greatly increase the effective specific surface area. Moreover, heteroatom-doping and oxygen-containing groups on the surface of graphene can obtain extra redox capacitance and achieve good wettability between the electrode and the electrolyte. The superior structure means that NO-3DG@CNC-based multi-style supercapacitors, such as aqueous-system, ionic-system, and lithium-ion capacitors etc., all show high energy density, high power density and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Proper hybridization of different kinds of materials into tailored structures is a highly effective way to fabricate advanced anode materials for sodium ion batteries. In this work, mulberry-like Sn2Nb2O7/SnO2 nanoparticles (≈40 nm) homogeneously anchored on 3D carbon networks (indicated with M-Sn2Nb2O7/SnO2@3DC) were prepared through a facile one-step high temperature calcination technique. In the constructed architecture, Sn-based materials with high specific capacity, Nb-based materials with excellent structural stability and 3D carbon networks with high electron conductivity were well integrated into a smart system. The 3D carbon networks not only act as a buffer material to prevent pulverization, but also serve as a conductive matrix, while the in situ formed amorphous NaxNb2O5 substrate from Sn2Nb2O7 can restrain the volume variation to prevent Sn from aggregation and pulverization during cycling. This unique “self-buffering” effect can remarkably enhance the structural integrity of the electrode. As a result, when tested as a sodium ion battery anode, the as-synthesized hybrid exhibited relatively high reversible capacity (300 mA h g−1 at the current density of 100 mA g−1), outstanding high-rate capability (119 mA h g−1 even at the high current density of 10 A g−1) and extremely long cycling stability (130 mA h g−1 at the current density of 5.0 A g−1 for 5000 cycles). Such excellent electrochemical performance demonstrates the potential use of the Sn2Nb2O7/SnO2@3D carbon composite as an anode material for high-performance sodium-ion batteries. [ABSTRACT FROM AUTHOR]

SnO2 is considered a promising anode candidate for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), but suffers from the low electrical conductivity and severe volume variation during repetitive cycling. To circumvent these issues, we developed novel interconnected sandwiched carbon-coated hollow nanostructures, i.e., carbon–shell/SnO2–nanocrystal–layer/hollow–carbon–core (C@SnO2@C HNSs), in which ultrasmall SnO2 nanocrystals (2–5 nm) were tightly confined between the carbon shell and the hollow carbon core. Such a unique structure can not only protect the active materials from direct exposure to the electrolyte as well as restrain the migration and pulverization of the SnO2, but also offer rich void space for buffering the volume changes and complement the electron conductivity of the active materials, thus achieving remarkably enhanced electrical conductivity and structural integrity of the whole electrode. As a consequence, this C@SnO2@C HNS electrode exhibited an extremely outstanding long-life high-rate cycling stability for both LIB and SIB anodes, such as only 8% capacity loss after 1000 cycles at 10 A g−1 for LIB anode and only 10% capacity loss after 3000 cycles at 4.6 A g−1 for SIB anodes. As far as we know, this is the best high-rate cycle performance ever reported for SnO2-based SIB anodes. [ABSTRACT FROM AUTHOR]

A convenient and scalable in situ chemical vapor deposition (CVD) method is developed for one-step fabrication of sandwiched graphene sheets which were filled with yolk–shell γ-Fe2O3 nanoparticles encapsulated with graphene shells (YS-γ-Fe2O3@G-GS). Such a unique architecture can be applied to produce an excellent lithium ion battery (LIB) anode. As a result, long-term cycling stability at high rates (a high capacity of 663.7 mA h g−1 is achieved at 2 A g−1 and maintained at approximately 96.6% even after 1500 cycles) and superior rate capability (1173 mA h g−1 at 0.1C, 989 mA h g−1 at 0.2C, 827 mA h g−1 at 0.5C, 737 mA h g−1 at 1C, 574 mA h g−1 at 2C, 443 mA h g−1 at 5C, and 350 mA h g−1 at 10C; 1C = 1 A g−1) can be obtained when YS-γ-Fe2O3@G-GS is used as an LIB anode. As far as we know, this is the best rate capacity and longest cycle life ever reported for an Fe2O3-based LIB anode. [ABSTRACT FROM AUTHOR]

The structural damage induced by huge volume change during lithiation/delithiation results in poor cycle stability of tin-based anode materials, which becomes the major obstacle to their practical application. In this work, we fabricated three-dimensional (3D) porous bowl-shaped carbon cages interspersed with carbon coated Ni–Sn alloy nanoparticles (Ni3Sn2 and Ni3Sn4; 10–30 nm) by a freeze-drying method with self-assembled NaCl as a template followed by annealing. Both Ni3Sn2/C and Ni3Sn4/C exhibit excellent electrochemical performance as anode materials for lithium-ion batteries. In particular, the Ni3Sn4/C nanocomposites exhibit superior rate capability (735, 661, 622, 577, 496, and 377 mA h g−1 at 0.1, 0.2, 0.5, 1, 2, and 5 A g−1, respectively) and excellent cycling stability (568 mA h g−1 at 0.5 A g−1 for the second cycle and gradually increased to 732 mA h g−1 after 200 cycles). The superior electrochemical performance is attributed to the synergetic effect of Ni–Sn alloy nanoparticles and 3D porous bowl-shaped carbon networks. The uniformly embedded Ni–Sn alloy nanoparticles can effectively alleviate the absolute stress/strain and shorten the Li+ diffusion path, and Ni in the Ni–Sn alloy acts as a buffer to suppress the volume expansion. Moreover, the 3D bowl-shaped carbon networks with high conductivity can provide abundant space for volume expansion, suppress the agglomeration of Ni–Sn nanoparticles, ensure the structural integrity, and facilitate lithium-ion diffusion as well as electron transportation. [ABSTRACT FROM AUTHOR]

Layered transition metal dichalcogenides (TMDs), such as MoS2, WS2, MoSe2, WSe2, etc., have received considerable interest recently due to their unique properties and fascinating applications. In this work, we proposed a NaCl template-assisted in situ chemical vapor deposition (CVD) strategy for synthesizing high-quality two-dimensional (2D) WS2, MoS2, MoSe2 and WSe2 nanosheets with a single-crystalline structure on a large scale. During the synthesis, 3D self-assembly of cubic NaCl particles can not only provide smooth surfaces to support the lateral growth, but also create a 2D confined space to restrict the thickening of TMD nanosheets, while the high-temperature annealing during the CVD process ensures high crystallinity and structural stability as well as remarkably promoting the conductivity of the TMD nanosheets. When evaluated as sodium-ion battery anodes, the representative WS2 nanosheets exhibited a high reversible specific capacity of 453 mA h g−1 at a current density of 0.1 A g−1, an excellent cycling performance and a greatly enhanced rate capability. The charge storage mechanism together with the microstructure evolution of WS2 nanosheets during the sodiation/disodiation processes is responsible for their superior sodium storage performance. [ABSTRACT FROM AUTHOR]

Constructing a 3D porous architecture from 2D MoS2 nano-building blocks has been considered as a promising approach to prevent restacking and thus achieve superior properties in energy conversion and storage, catalysis, sensors, and so on. In this work, a novel salt (NaCl) template-assisted solid-phase synthesis strategy is developed to fabricate a new type of MoS2 with a robust 3D honeycomb-like structure without the necessity to use a solution reaction. As a demonstration of structural advantages, the 3D honeycomb-structured MoS2 with a highly crystalline architecture and intimate interfacial bonding between adjacent MoS2 walls is utilized as a lithium-ion battery anode, exhibiting an unprecedented initial coulombic efficiency (∼93.5%), large specific capacity, high rate capability and excellent cycle stability. [ABSTRACT FROM AUTHOR]

Metallic Sn has triggered significant research efforts as a lithium ion battery anode due to its high theoretical capacity and low-cost. However, the structural damage induced by the severe volume change of Sn and the continuous interfacial reaction due to the electrolyte remain two major challenges to hinder the practical applications of Sn-based anodes. In this work, we report the fabrication of a novel 3D composite architecture that is constructed by flexible graphene/Sn sandwich nanosheets synthesized by an in situ catalytic synthesis strategy, which relies on in situ formation and spatial entrapment of active Sn nanoparticles (NPs) inside the simultaneously catalytically formed 3D porous graphene. Such a unique architecture not only provides robust protection against the aggregation and volume changes of Sn NPs, and thus effectively avoids the direct contact between entrapped Sn and the electrolyte and enables the interfacial and structural stabilization of entrapped Sn NPs during cycling, but also ensures highly favorable three dimensional transport kinetics for both electrons and lithium ions in the whole electrode. As a result, this 3D composite anode exhibits very high reversible capacity, superior rate capability, and extremely excellent cycle stability even at high rates (650 mA h g−1 at 2 A g−1 over 500 cycles). [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) hierarchical porous carbons (indicated with 3D HPCs) were synthesized via a simple one-pot method using the self-assembly of various water-soluble NaX salts (X: Cl−, CO32−, SiO32−) as structure-directing templates. By controlling crystallization and assembly of multi-scale salts via a freeze-drying process, 3D porous carbon networks with tailored pore size distribution have been generated by calcining the salts/glucose self-assembly followed by removing the 3D self-assembly of NaX salts via simple water washing. When their applications were evaluated for supercapacitor electrodes as an example, the as-constructed 3D HPCs with large surface area, high electron conductivity, facile electrolyte penetration and robust structure exhibited excellent capacitive performance, namely, high specific capacitance (320 F g−1 at 0.5 A g−1), outstanding high rate capacitance retention (126 F g−1 at 200 A g−1), and superior specific capacitance retention ability (nearly no discharge capacity decay between 1000 and 10 000 continuous charge–discharge cycles at a high current density of 5 A g−1). Based on our soluble salt self-assembly-assisted synthesis concept, it was revealed that salts in seawater are also very suitable for low-cost and scalable synthesis of 3D HPCs with good capacitive performance, which pave the way for advanced utilization of seawater. [ABSTRACT FROM AUTHOR]

A chain-like carbon nanostructure, which we call as carbon nano-chains (CNCs), was synthesized through chemical vapor deposition (CVD). The influence of growth conditions (such as growth temperature, time and gas ratio) during CVD process on the carbon structures and the growth mechanism of the CNCs were investigated. To explore the potential application as electrode materials of supercapacitors, the electrochemical performances of the CNCs and the CNCs activated with KOH have been tested. The results indicated that the original CNCs exhibit relatively high specific surface area, high purity and regular framework, and favor growth at a moderate temperature and mild gas ratio. After activation, the CNCs have much improved specific surface area and porous structure. The electrochemical performance investigations showed that the activated CNCs have a power density of 159.6 kW kg-1 and an energy density of 15.5 W h kg-1, as well as excellent cycle stability, which is very superior to the original CNCs. This simple and low-cost preparation process and the superb electrochemical performance suggest great potential applications of activated CNCs in supercapacitors. [ABSTRACT FROM AUTHOR]

A high-quality ultrathin anatase TiO[sub 2] nanosheet (ANT)/reduced graphene oxide (RGO) composite is successfully prepared by a simple one-step hydrothermal synthetic route. The unique 2-D integrative features and mesoporous characteristic of the ultrathin ATN/RGO composite with a large surface area and outstanding stability are very favorable for lithium storage. A high initial discharge capacity (256.4 mA h g[sup -1] at 0.2C), a high initial Coulombic efficiency (86%), a high rate capability (225.7, 202, 183, 157, 118 and 88.3 mA h g[sup -1] at 0.5, 1, 2, 5, 10, and 20C, respectively, 1C = 167.5 mA h g[sup -1]), and a superior cyclability (174.2 mA h g[sup -1] after 200 cycles at 1C and 112.9 mA h g[sup -1] after 260 cycles at 10C) are achieved by using the ultrathin ATN/RGO composite as an anode material for lithium-ion-batteries. A detailed comparative study of the electrochemical properties of P25 nanoparticles, ATNs, ATN/RGO, and ultrathin ATN/RGO composites reveals that the significantly enhanced lithium storage capability is attributed to the ultrathin TiO[sub 2] nanosheets with short ion diffusion paths facilitating Li+ insertion/ extraction, RGO conductive supports for fast electron transport, and the extra Li storage at the RGO/ TiO[sub 2] interface. [ABSTRACT FROM AUTHOR]

A facile and scalable strategy for the synthesis of discrete, homogeneous and small (mostly 5–15 nm) Fe3O4 nanocrystals embedded in a partially graphitized porous carbon matrix was developed, which involved the simple mixing of a metal precursor (Fe(NO3)3·9H2O), a carbon precursor (C6H8O7), and a dispersant (NaCl) in an aqueous solution followed by calcination at 600 °C for 2 h under Ar. As the anode materials for lithium-ion batteries, the Fe3O4/carbon composite with 55.24 wt% Fe3O4 exhibited superior electrochemical performances, such as high reversible lithium storage capacity (834 mA h g−1 at 1 C after 60 cycles, 1 C = 924 mA g−1), high Coulombic efficiency (∼100%), excellent cycling stability, and superior rate capability (588 mA h g−1 at 5 C and 382 mA h g−1 at 10 C). These excellent electrochemical performances could be attributed to the robust porous carbon matrix with a partially graphitized structure for embedding a mass of small Fe3O4 nanocrystals, which not only provided excellent electronic conductivity, short transportation length for both lithium ions and electrons, and enough elastic buffer space to accommodate volume changes upon lithium insertion/extraction, but also could effectively avoid agglomeration of the Fe3O4 nanocrystals and maintain the structural integrity of the electrode during the charge–discharge process. It is believed that the Fe3O4/carbon composite synthesized by the current method is a promising anode material for high energy and power density lithium-ion batteries. [ABSTRACT FROM AUTHOR]