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[Display omitted] In this paper, we have developed a simple and efficient sulfur-amine chemistry strategy to prepare a three-dimensional (3D) porous Ti 3 C 2 T x composite with large amounts of N and S terminal groups. The well-designed 3D macroporous architecture presents enlarged interlayer spacing, large specific surface area, and unique porous structure, which successfully solves the re-stacking issue of MXene during storage and electrode fabrication. It is the amount of concentrated hydrochloric acid added to the S-EDA (ethylenediamine)/MXene colloidal suspension that is critical to the formation of 3D morphology. In addition, N and S terminals on MXene could improve the adsorption ability of K+. Owing to the synergistic effect of the structure design and terminal modification, the N, S codoped three-dimensional porous Ti 3 C 2 T x (3D-NSPM) material shows a high surface capacitive contribution and rapid diffusion kinetics for K+ and Na+. As a result, the as-prepared 3D-NSPM delivers high reversible capacity (237 and 273 mAh g−1 at 0.1 A g−1 for PIBs and SIBs, respectively), superb cycling stability (84.9% capacity retention after 10,000 cycles at 1 A g−1 in PIBs and 74.0% capacity retention after 2200 cycles at 1 A g−1 in SIBs), and excellent rate capability (111 and 196 mAh g−1 at 5 A g−1 for PIBs and SIBs, respectively), which are superior to other MXene-based anodes for PIBs and SIBs. Moreover, the described strategy provides a new insight for constructing the 3D porous structure from 2D building blocks beyond MXene. [ABSTRACT FROM AUTHOR]

The synergy between iron doping and (1 1 1) facet engineering in Fe-NiSe octahedron reinforces catalytic activity for IRR to yield impressive photovoltaic performance of DSSCs. [Display omitted] • The possibility of Fe-NiSe (1 1 1) as CE catalysts was investigated by DFT calculation. • The well-defined Fe-doped NiSe octahedron with (1 1 1) plane was synthesized. • Synergy between doping and facet engineering reinforces electrochemical behavior. • PCE can be further enhanced by introducing Fe heteroatom into NiSe (1 1 1). Reasonable design of cost-effective counter electrode (CE) catalysts for triiodide (I 3 −) reduction reaction (IRR) by simultaneously combining heteroatom doping and facet engineering is highly desired in iodine-based dye-sensitized solar cells (DSSCs), but really challenging. Herein, the density function theory (DFT) calculations were first conducted to demonstrate that the Fe-doped NiSe (1 1 1) showed an appropriate adsorption energy for I 3 −, increased number of metal active sites, reinforced charge-transfer ability, and strong interaction between 3 d states of metal sites and 5 p state of I 1 atoms in I 3 −, compared to NiSe (1 1 1). Based on this finding, the well-defined Fe-NiSe octahedron with exposed (1 1 1) plane (marked as Fe-NiSe (1 1 1)) and NiSe octahedron with the same exposed plane (named as NiSe (1 1 1)) are controllably synthesized. When the as-prepared Fe-NiSe (1 1 1) and NiSe (1 1 1) worked as CE catalysts, Fe-NiSe (1 1 1) exhibits improved electrochemical performance with higher power conversion efficiency (PCE) than NiSe (1 1 1), providing new opportunity to replace precious Pt for DSSCs. [ABSTRACT FROM AUTHOR]

Following the ammonia treatment, the pores created by the folds allow for electrolyte storage and facilitate ion transport. The interlayer spacing between MXene nanosheets widens due to the volume increase when water freezes. The generous ion transport paths and redox-active ammonium ions offer higher specific capacity and faster reaction kinetics. [Display omitted] Ti 3 C 2 T x MXene demonstrates excellent potential as an anode material for sodium-ion capacitors. However, the narrow interlayer spacing and self-stacking phenomenon limit its applicability. In this study, we demonstrate an easy two-step method involving freezing and crumpling of MXene nanosheets to improve their Na-ion storage via the addition of ammonium ions (referred to as FCM nanosheets). Flat MXene particles aggregate and undergo folding in an alkaline solution. Ammonium ions can penetrate the gaps between MXene nanosheets, expanding interlayer spaces and inducing the formation of folds. Compared to MXene nanosheets, FCM nanosheets exhibit improved ion transfer kinetics and additional high capacity owing to the intercalated ammonium ions. The manufactured FCM anode exhibits remarkable electrochemical properties, including a high specific capacity of 313 mAh g−1 and stability over 15,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The carbonized recycled melamine sponge obtained excellent low-cost porous matrix. • FeNi@NCS shows lower reaction potential and higher electron transfer ability on UOR. • Successfully assembled the DBHPFC using urine as fuel. • DUHPFC presents excellent open circuit voltage. The direct urea fuel cell (DUFC) is a power generation equipment with urea-rich wastewater or urine as fuel source. It has the unique ability to purify sewage while simultaneously generating electricity, making it a highly efficient and environmentally friendly option. In this paper, pomegranate seed-like Ni nano-blocks and Fe nanosheets were synthesized by electrodeposition and chemical reduction and attached to the carbonized melamine sponge matrix. The N -doped carbon sponge (NCS) provided a large number of polyhedral holes, which allowed for efficient gas escape through channels. The combination of Fe reduces the initial urea oxidation potential, reaction activation energy and reaction resistance. The synthesized FeNi supported on N -doped carbon sponge composite (FeNi@NCS) has a catalytic current density of 625 mA cm−2 and a Tafel slope of 42.51 mV dec−1 for urea electrooxidation reaction (UOR). Assembling the direct urine-hydrogen peroxide fuel cell (DUrHPFC) resulted in the highest performance output. The open circuit voltage (OCV) was 0.98 V, and the peak power density reached 9.61 mW cm−2. The results show that the prepared catalyst provides an opportunity to solve the problems that hinder the development of urea green cycle at present. [ABSTRACT FROM AUTHOR]

[Display omitted] MoS 2 is regarded as a hopeful anode candidate for sodium-ion batteries (SIBs) due to their various merits such as high specific capacity, abundant raw material reserves and low cost. However, their practical application is impeded by unsatisfied cycling ability due to the intense mechanical stress and unstable solid electrolyte interphase (SEI) during Na+ insertion/extraction process. Herein, spherical MoS 2 @polydopamine derived highly conductive N -doped carbon (NC) shell composites (MoS 2 @NC) are designed and synthesized to promote the cycling stability. The internal MoS 2 core is optimized and restructured from the original micron-sized block to the ultra-fine nanosheets during initial 100–200 cycles, which not only improves the utilization of electrode materials but also shortens the ion transport distance. The outer flexible NC shell effectively maintains the original spherical structure of the overall electrode material and prevents the occurrence of large-scale agglomeration, which is conducive to form a stable SEI layer. Therefore, the core–shell MoS 2 @NC electrode presents a remarkable cyclic stability and a capable rate performance. Under a high rate of 20 A g−1, the high capacity of 428 mAh g−1 can be acquired after over ultra-long 10,000 cycles without obvious capacity loss. Moreover, the MoS 2 @NC‖Na 3 V 2 (PO 4) 3 full-cell assembled by employing commercial Na 3 V 2 (PO 4) 3 cathode can achieve a high capacity retention of 91.4% after 250 cycles at 0.4 A g−1. This work reveals the promising prospect of MoS 2 -based materials as anode of SIBs, and also has some inspirations on the structural design for conversion-type electrode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Exploring capable and universal electrode materials could promote the development of alkalis (Li, Na, K) ion batteries. 2D MXene material is an ideal host for the alkalis (Li, Na, K) ion storage, but its electrochemical performance is limited by serious re-stacking and aggregation problems. Herein, we cleverly combined electrostatic self-assembly with gas-phase vulcanization method to successfully combine Ti 3 C 2 T x -MXene with ultra-long recyclability and high conductivity with MnS, which presents high specific capacity but poor conductivity. The as-prepared 3D hierarchical Ti 3 C 2 T x /MnS composites have an unique sandwich-like constituent units. The tiny MnS nanoparticles are restricted between the Ti 3 C 2 T x layers and play a key role in expanding the Ti 3 C 2 T x interlayer spacing. As a result, the 3D Ti 3 C 2 T x /MnS composites as the anode of LIBs exhibits a superior capacities of 826 and 634 mAh/g after 1000 and 3000 cycles at 0.5 and 1.0 A/g, respectively. More importantly, we reveal the reaction mechanism that the specific capacity first increases and then gradually stabilizes with the increase of charge and discharge cycle times when the as-prepared 3D Ti 3 C 2 T x /MnS was used as the anode of LIBs. In addition, we have also used this material in SIBs and PIBs and achieved remarkable electrochemical capability, with a specific capacity of 107 mAh/g after 2500 cycles at 0.5 A/g or 127 mAh/g after the 2000th cycle at 0.2 A/g, respectively. [ABSTRACT FROM AUTHOR]

MoSSe nanosheets anchored carbon tubes (CTs) were prepared with facile hydrothermal method and further selenized carbonization treatment. The hollow tubular carbon skeletons with abundant functional groups can regulate the uniform growth of MoS 2 clusters. In the subsequent step, the selenation treatment can extend the interlayer spacing of MoS 2 and form chemical bond (Mo N C) between the interface of MoSSe and CTs, which can effectively facilitate the transport of electron/ions. As the electrode materials for both SIBs and KIBs, the MoSSe@CTs presented a high and efficient Na+/K+ ions storage capability and good cycling stability. [Display omitted] • The tubular carbon skeletons expose abundant active sites for MoS 2 nanosheets growth. • The selenization treatment can expand the interlayer spacing of MoS 2 nanosheets. • The unique structure can improve rate capability and cycling stability of batteries. The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS 2 ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS 2) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g−1 at 1 A g−1 and retains a stable reversible capacity of 465 mAh g−1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg−1 at 1 A g−1 and a good cycling stability (maintains at 272 mA hg−1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries. [ABSTRACT FROM AUTHOR]

MoSSe nanosheets anchored carbon tubes (CTs) were prepared with facile hydrothermal method and further selenized carbonization treatment. The hollow tubular carbon skeletons with abundant functional groups can regulate the uniform growth of MoS 2 clusters. In the subsequent step, the selenation treatment can extend the interlayer spacing of MoS 2 and form chemical bond (Mo N C) between the interface of MoSSe and CTs, which can effectively facilitate the transport of electron/ions. As the electrode materials for both SIBs and KIBs, the MoSSe@CTs presented a high and efficient Na+/K+ ions storage capability and good cycling stability. [Display omitted] • The tubular carbon skeletons expose abundant active sites for MoS 2 nanosheets growth. • The selenization treatment can expand the interlayer spacing of MoS 2 nanosheets. • The unique structure can improve rate capability and cycling stability of batteries. The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS 2 ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS 2) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g−1 at 1 A g−1 and retains a stable reversible capacity of 465 mAh g−1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg−1 at 1 A g−1 and a good cycling stability (maintains at 272 mA hg−1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] Polymer materials containing C 6 rings and C O become promising electrode materials for high-performance lithium ion batteries (LIBs). However, the poor electronic conductivity severely restricts its further application. Herein, we design and construct a pyromellitic dianhydride anhydride anthraquinone/reduced graphene oxides (PMAQ/rGO-40) composite as an anode material for LIBs. The PMAQ is uniformly wrapped by conductive rGO nanosheets. The PMAQ/rGO-40 electrode without additional conductive agents displays a discharge capacity of 253 mAh g−1 over 3000 cycles under 2A g−1, which is higher than that of the PMAQ electrode with conductive agents. Meanwhile, a capacity of 196 mAh g−1 is achieved under 5A g−1. The enhanced cycling performance and rate ability are attributed to the rGO conductive network, which promotes electronic transport capability. In addition, the lithium ion storage mechanism and kinetics in the PMAQ/rGO-40 are investigated. The excellent electrochemical performance shows the potential application of the PMAQ/rGO composite anode material for high performance LIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] Rechargeable metal batteries such as non-aqueous Li metal batteries and aqueous Zn metal batteries have received increasing attention due to the benefits of the high-energy metal anode. However, the dendric growth on the metal anode extremely leads to restricted cycling performance and potential safety issues. Herein, the MXene-modified conductive framework (MCF) is designed and fabricated as a universal current collector of anode for non-aqueous Li metal batteries and aqueous Zn metal batteries to suppress the dendric Li and Zn growth. The MCF exhibits the merits of good lithiophilicity and zincophilicity, enables an easy Li/Zn nucleation process, and possesses high plating/stripping reversibility. After plating Li/Zn, MCF@Li and MCF@Zn realize a dendrite-free surface, facilitating Li/Zn plating/stripping kinetics. The MCF@Li and MCF@Zn symmetric cell shows a low overpotential of 13 mV at 1 mA cm−2 after 900 cycles and 64 mV at 5 mA cm−2 after 750 cycles (1 mAh cm−2), respectively. Furthermore, the non-aqueous MCF@Li||LiFePO 4 full cells and the aqueous MCF@Zn||active carbon capacitors are assembled and present stable cycling ability and improved rate performance with low polarization. This work provides a universal current collector strategy to meet the requirements of non-aqueous and aqueous metal anodes, which may inspire more designs for metal-based energy storage systems. [ABSTRACT FROM AUTHOR]

[Display omitted] The development of efficient catalysts for hydrogen evolution reaction (HER) from water splitting is one of the most promising strategies to achieve the goal of peak carbon dioxide emissions and carbon neutrality. Herein, Ru nanoclusters decorated MoSe 2 nanosheets supported on a Crepis tectorum fluff biomass-derived hollow carbon tube (Ru-MoSe 2 /CMT) are prepared as the HER catalysts in both alkaline and acidic conditions. The Ru modification induces the transformation of MoSe 2 from 2H phase to 1T phase. Benefiting from the strong water dissociation ability of Ru, Ru-MoSe 2 /CMT exhibits a low overpotential of 70 mV with a Tafel slope of 39 mV dec-1 in 1 M KOH. Furthermore, the assembled Ru-MoSe 2 /CMT || RuO 2 system with a low cell voltage of 1.54 V at 10 mA cm−2 exhibits outstanding overall water splitting performance superior to Pt/C || RuO 2 system. The Ru-MoSe 2 /CMT || RuO 2 system also achieves the excellent stability of up to 30 h in 1 M KOH. The synergy effect between Ru and MoSe 2 , as well as the improved electron transfer kinetics provided by the biomass-derived carbon substrate together contribute to the excellent HER activity of Ru-MoSe 2 /CMT. [ABSTRACT FROM AUTHOR]

[Display omitted] • RuNi 1 Co 1 alloy nanoparticles embedded in the hollow carbon tubes with a mosaic structure was prepared. • The DFT calculations indicate that the addition of Ru could optimize the hydrogen adsorption free energy of Ni and Co sites. • RuNi 1 Co 1 @CMT exhibits considerable HER and OER activities, and a low cell voltage was required for the overall water splitting system. • RuNi 1 Co 1 @CMT || RuNi 1 Co 1 @CMT overall water splitting system can be driven by a solar panel, which realized green and sustainable hydrogen production. The development of efficient bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for reducing the cost of hydrogen production by water splitting. Herein, hollow microtubes composed of RuNi 1 Co 1 alloy nanoparticles uniformly embedded in the carbon matrix (RuNi 1 Co 1 @CMT) are prepared through a simple impregnation followed by reduction. Benefiting from the unique mosaic structure and the synergistic effect between Ru and NiCo, RuNi 1 Co 1 @CMT achieves more exposed active sites and improved reaction kinetics. As a consequence, RuNi 1 Co 1 @CMT exhibits considerable catalytic activities with the overpotentials of 78 mV for HER and 299 mV for OER at 10 mA cm−2 in 1 M KOH. In addition, RuNi 1 Co 1 @CMT exhibits excellent stability for up to 30 h in both HER and OER processes at 20 mA cm−2, which is attributed to the protection of the RuNi 1 Co 1 alloy particles by the carbon layer. Furthermore, the assembled RuNi 1 Co 1 @CMT || RuNi 1 Co 1 @CMT overall water splitting system shows a cell voltage of 1.58 V at 10 mA cm−2. The density functional theory (DFT) calculations indicate that the addition of Ru can optimize the hydrogen adsorption free energy of Ni and Co sites. Finally, a solar panel-driven water splitting device is built, which can realize green and sustainable hydrogen production. The fabrication of RuNi 1 Co 1 @CMT provides a new way for the preparation of effective alloy nanomaterials for energy storage and conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoSe 2 -MoSe 2 (1–1)/rGO has good HER activity in both acidic and alkaline media. • The CoSe 2 -MoSe 2 (1–1) nanosheets uniformly decorate the rGO matrix. • DFT results verify CoSe 2 -MoSe 2 (1–1) heterostructure owns small band gap and ΔG H*. • The rGO matrix and heterojunction structure improve the electronic conductivity. It is important to develop novel energy to solve energy shortage and environmental problems. Hydrogen evolution reaction (HER) is envisaged as a viable technology that can be used to develop sustainable clean energy. Herein, we report a catalyst with CoSe 2 -MoSe 2 heterostructure grown on reduced graphene oxide with an optimum Co/Mo proportion of 1:1 (CoSe 2 -MoSe 2 (1–1)/rGO). It exhibits good HER activities in both acidic and alkaline conditions. The CoSe 2 -MoSe 2 (1–1)/rGO shows an overpotential of 107 mV at 10 mA cm−2 with a Tafel slope of 56 mV dec−1 under acidic condition. Meanwhile, CoSe 2 -MoSe 2 (1–1)/rGO also presents an overpotential of 182 mV at 10 mA cm−2 and with a Tafel slope of 89 mV dec−1 under alkaline condition. These impressive performances of the catalyst are mainly due to the excellent electronic transmission capability of rGO and the abundant active sites of CoSe 2 -MoSe 2 heterostructure as well as the optimized hydrogen adsorption energy of CoSe 2 -MoSe 2 interface. The design of CoSe 2 -MoSe 2 (1–1)/rGO provides a meaningful guide for manufacturing electrode in energy storage and conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeSe 2 -MoSe 2 (1-1)/rGO has good HER activity in both acidic and alkaline media. • FeSe 2 -MoSe 2 (1-1)/rGO has well stability in both acidic and alkaline media. • On the morphology, FeSe 2 -MoSe 2 nanoparticles uniformly decorate the rGO matrix. • DFT results verify the FeSe 2 -MoSe 2 (1-1)/rGO owns small work function. It is of great significance to develop inexpensive and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER). In this work, we synthesized iron molybdenum selenide (FeSe 2 -MoSe 2) loaded on reduced graphene oxide (FeSe 2 -MoSe 2 /rGO) by a one-step hydrothermal method. We further optimized the Fe/Mo ratio and determined the best ratio to be 1-1. In acidic (or alkaline) solution, the optimized FeSe 2 -MoSe 2 (1-1)/rGO has a small Tafel slope of 55 (or 80) mV dec−1 and needs an overpotential of 101 (or 178) mV to achieve 10 mA cm−2. These good properties are mainly due to the structure of bimetallic selenides combining rGO. Moreover, rGO enhances the electrical conductivity. Furthermore, the synergistic effect between FeSe 2 -MoSe 2 (1-1) and rGO results in better HER performance. Density functional theory (DFT) calculation proves that FeSe 2 -MoSe 2 (1-1)/rGO has a small work function. Based on our reasonable design and analysis, FeSe 2 -MoSe 2 (1-1)/rGO is expected to be an efficient and robust catalyst for large-scale applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrocatalytic water splitting used for generating clean and sustainable hydrogen (H 2) can be very promising to address current energy shortage and associated environmental issues. However, this methodology is severely impeded by the tardy oxygen evolution reaction (OER). Hence, designing a preferable kinetics and thermodynamics oxidation reaction that supersede OER is very significant for the energy-saving production of H 2. Herein, hollow needle-like copper cobalt sulfide was constructed on carbon cloth (CuCo 2 S 4 /CC) as a bifunctional electrocatalyst to accelerate H 2 generation and simultaneously convert ethanol into value-added acetic acid. Thanks to the synergistic effect and unique structure of Cu and Co, CuCo 2 S 4 /CC displays superior catalytic activity and durability in ethanol oxidation reaction (EOR) with a low potential of 1.38 V vs. RHE (@10 mA cm−2). Meanwhile, it exhibits excellent hydrogen evolution reaction (HER) performance. The homemade CuCo 2 S 4 /CC//CuCo 2 S 4 /CC ethanol–water electrolyser only demands a voltage of 1.59 V to deliver 10 mA cm−2, 150 mV less than that used for ordinary water splitting. This shows that the ethanol–water electrolyser elaborated here holds encouraging potential in the energy-saving production of H 2 and oxidation of ethanol into value-added acetic acid. This present work may open the way for the rational design of other electrocatalysts for efficient biomass oxidation reaction and relevant H 2 production applications. [ABSTRACT FROM AUTHOR]

[Display omitted] MoS 2 is regarded as an attractive anode material for lithium-ion batteries due to its layered structure and high theoretical specific capacity. Its unsatisfied conductivity and the considerable volume change during the charge and discharge process, however, limits its rate performance and cycling stability. Herein, 3D tremella-like nitrogen-doped carbon encapsulated few-layer MoS 2 (MoS 2 @NC) hybrid is obtained via a unique strategy with simultaneously poly-dopamine carbonization, and molybdenum oxide specifies sulfurization. The three-dimensional porous nitrogen-doped carbon served both as a mechanical supporting structure for stabilization of few-layers MoS 2 and a good electron conductor. The MoS 2 @NC exhibits enhanced high rate performance with a specific capacity of 208.7 mAh g−1 at a current density of 10 A g−1 and stable cycling performance with a capacity retention rate of 85.7% after 1000 cycles at 2 A g−1. [ABSTRACT FROM AUTHOR]

Binary metal niobium oxides can offer a higher specific capacity compared to niobium pentoxide (Nb 2 O 5) and thus are ideal anode candidates for lithium ion capacitors (LICs). However, their lower electronic conductivity limits their ability to achieve high energy and power densities. In this paper, one-dimensional (1D) copper niobate (CuNb 2 O 6) nanowires are successfully prepared by electrospinning technology and then immobilized on two-dimensional (2D) reduced graphene oxide (rGO) nanosheets to form a unique 1D nanowire/2D nanosheet CuNb 2 O 6 /rGO structure. The 1D/2D CuNb 2 O 6 /rGO electrode exhibits a high specific capacity of 312.2 mAh g−1 at 100 mA g−1 as the anode of LICs. The proposed Li+ storage mechanism of the CuNb 2 O 6 anode involves CuNb 2 O 6 decomposition into lithium niobate (Li 3 NbO 4) and copper (Cu) during the initial lithium insertion process. The intercalation-type Li 3 NbO 4 will further serve as the host to Li+ and the inactive Cu phase will act as a conductive network for electron transportation. Furthermore, the energy density of the assembled CuNb 2 O 6 /rGO//activated carbon (CuNb 2 O 6 /rGO//AC) device could achieve a value as high as 92.1 Wh kg−1 and could thus be considered as a possible alternative electrode material for high energy and power LICs. [ABSTRACT FROM AUTHOR]

The Mo 2 C@C catalyst was prepared by the calcination method under the argon gas flow of the activated walnut shell-ammonium heptamolybdate hybrid powder mixture, enhancing the electrocatalytic hydrogen evolution process. • The waste walnut shell powder was chosen as the carbon source for HER catalysts. • The walnut shell powders derived carbon matrix can enhance the electron transfer. • The open pores can facilitate electrolyte permeation and hydrogen release. Herein, we choose the waste walnut shell as the carbon source, and ammonium heptamolybdate as the molybdenum source to prepare the β-Mo 2 C catalyst supported on carbon matrix (Mo 2 C@C) by the calcination method for hydrogen evolution reaction (HER). The open pores in the porous Mo 2 C nanoparticle clusters can facilitate electrolyte permeation and hydrogen molecules release as well as the carbon matrix can enhance the conductivity. As a result, the optimal Mo 2 C exhibits an efficient HER performance, with an overpotential of 140 mV at 10 mA cm−2 and a Tafel slope of 63 mV dec−1 as well as excellent electrochemical stability. The strategy changing waste walnut shell into the effective catalysts sets an example for the searching and designing rational energy materials. [ABSTRACT FROM AUTHOR]

A three-dimensional free-standing hard carbon (FHC) electrode is synthesized by carbonizing the hemp haulm and employed as anode for sodium-ion batteries directly. A high current charging-discharging process is carried out to reconstruct surface structure of the FHC. Surface reconstructed FHC display a high capacity of 256 mAh/g and enhanced rate ability. With the formation of order surface structure, the plateau capacity increase and more sodium ions can insert into the FHC. This work demonstrates the importance of surface structure for sodium ion diffusion and storage and provide a new strategy to design high-performance anode materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Unique nanostructure, high electrical conductivity, satisfactory energy density, and extraordinary cycling stability are important evaluation criteria for high-efficient energy storage devices. Herein, Fe 3 O 4 nanospheres are successfully in situ decorated on graphene nanosheets through an environmentally benign and facile solvothermal procedure. When utilized as an electrode for supercapacitor, the graphene/Fe 3 O 4 nanocomposite exhibits a notably enhanced specific capacity (268 F·g−1 at 2 mV·s−1) and remarkable cycling performance with 98.9% capacity retention after 10,000 cycles. Furthermore, the fabricated graphene/MnO 2 //graphene/Fe 3 O 4 asymmetric supercapacitor device displays a desirable energy density (87.6 Wh·kg−1) and superior cycling stability (93.1% capacity retention after 10,000 cycles). [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Flexible supercapacitor plays a progressively more important part in power source for smart electronic devices and how to enhance its energy density is the urgent issue to be addressed. Hence, a hybrid electrode of Polypyrrole@reduced graphene oxide hydrogel (PPy@rGOH) is synthesized via a combine hydrothermal treatment of GO solution to assemble hydrogel and subsequently in-situ electropolymerization preparation of PPy on the surface of graphene. Through controlling the time of electropolymerization, the resultant PPy@rGOH-20 s with high specific surface area exhibits an excellent specific capacitance of 340 F g−1 at a current density of 1 A g−1 and superior cycling stability of 87.4% capacitance retention after 10,000 charging/discharging cycles at 3 A g−1 in 1 M KNO 3. The assembled flexible asymmetric supercapacitor (FASC) by employing the PPy@rGOH-20s as positive electrode and pure rGOH as negative electrode presents a maximum operational voltage window of 1.6 V and high energy density of 46.9 W h kg−1, which is higher than polymer/carbon-based supercapacitors previously reported. [ABSTRACT FROM AUTHOR]

Architecture of electrode materials plays an important role in achieving favorable electrochemical performance via providing fast electronic transport pathway and shorten lithium ion diffusion distance. Herein, ultrafine CoP nanoparticles were successfully embedded in carbon nanorod, which were grown on the biomass-derived carbon (BC). When applied as anode materials for lithium-ion batteries, these CoP@C/BC displayed capable specific capacity, remarkable rate ability and outstanding long-term cycling performance. The capacity was governed by combination of diffusion-controlled and capacitive processes, according to quantitative kinetic analysis. The good electrochemical performance is attributed to hierarchical construction of nanosized CoP embedded in carbon nanorod and BC with high conductivity composite, which relieve the volume changing of CoP and provide large electrode/electrolyte interface. The present design of hierarchical architecture can be extended to other transition metal-based oxides, sulfide and phosphide electrode materials for high performance alkali metal ion batteries. [ABSTRACT FROM AUTHOR]

Pd-Au/TiC electrodes with various three-dimensional structures are obtained by the pulsed potential electro-deposition in PdCl 2 /HAuCl 4 electrolytes. The morphologies of Pd-Au/TiC composite catalysts are significantly dependent on the component of deposited solutions. The surface appearance of Pd-Au catalysts changes from rime-shaped structure, to feather-like construction, then to pineapple root-like structure and finally to flower-like configuration with the increase of PdCl 2 content in electrolytes. These particular three-dimensional structures may be very suitable for H 2 O 2 electro-reduction, which assures a high utilization of Pd-Au catalysts and provides a large specific surface area. The electro-catalytic activities of H 2 O 2 reduction on the Pd-Au/TiC electrodes improve as increasing the Pd content in Pd-Au alloy catalysts. The pineapple root-like Pd 5 Au 1 /TiC electrode reveals remarkably excellent electrochemical property and desirable stability for catalyzing H 2 O 2 reduction in acid media. The direct peroxide-peroxide fuel cells with a 10 cm 3 min −1 flow rate display the open circuit voltage (OCV) of 0.85 V and the peak power density of 56.5 mW cm −2 at 155 mA cm −2 with desirable cell stability, which is much higher than those previously reported. [ABSTRACT FROM AUTHOR]