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Sodium super-ionic conductor (NASICON) materials are believed as competitive cathodes for sodium-ion batteries, however, their practical application is still prohibited by the limited reversible capacity. In this study, the tri-metal NASICON structured Na 3 Mn 0.5 V 0.5 Ti(PO 4) 3 is designed to combine with reduced graphene oxide (NMVTP/rGO) as cathode material. Benefited from the multi-step redox couples of Mn, V, and Ti, NMVTP/rGO realizes high reversible capacity and wide operating voltage. The small sizes of Na 3 Mn 0.5 V 0.5 Ti(PO 4) 3 and rGO ensure the fast charge migration. The rGO inhibits the dissolution of electrode material. As a result, NMVTP/rGO exhibits large specific capacity of 284.6 mAh g−1 at 0.1C, high rate performance (170.2 mAh g−1 at 1C and 108.5 mAh g−1 at 5C), and good cyclic stability. This work demonstrates a new insight for designing tri-metal NASICON structured materials with high capacity for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

S-doped CoP nanoneedles assembled urchin-like structure on carbon cloth is prepared to demonstrate the boosting effects of nonmetal element doping and morphology controlling engineerings on OER performances for alkaline water splitting. [Display omitted] • S-doped CoP nanoneedles assembled urchin-like structure is grown on carbon cloth. • S doping brings more active sites and enhanced catalysis kinetics. • Nanoneedles assembled urchin-like structure benefit high surface area fast charge transfer. • Improved OER efficiency in alkaline media are obtained. The electrocatalysts with low-price and high-efficiency for oxygen evolution reaction (OER) are of significant importance for water splitting, which is believed as the promising technique for future sustainable energy system. Herein, sulfur is doped into carbon cloth supported CoP nanoneedles assembled urchin-like structure to acquire improved intrinsic catalysis efficiency, fast charge diffusion, and additional catalysis sites for enhanced OER performance. The specific urchin-like assembly structure is beneficial for highly exposed active sites and short charge transfer path for catalysis. Benefited from the advantages, the obtained sample exhibits advanced OER activity even better than RuO 2 in alkaline solution, achieving low overpotentials of 248 and 380 mV at current densities of 10 and 100 mA cm−2, respectively. This study may set a blueprint for exploring efficient transition metal pounds based catalyst for water splitting with nonmetal doping engineering. [ABSTRACT FROM AUTHOR]

Multicomponent metal selenides with heterostructures are believed to effectively activate the surface pseudocapacitive contribution and improve the electrochemical dynamics, thus achieving high-performance anodes for sodium ion batteries (SIBs). Herein, a carbon coated CoSe2/Sb2Se3 heterojunction (CoSe2/Sb2Se3@C) is designed and constructed via an ion-exchange reaction between Co and Sb, and the subsequent selenization step. It is found that the hetero-structure and carbon shell effectively boost the charge transfer in the CoSe2/Sb2Se3@C composite electrode. The highly pseudocapacitive Na+ storage contribution is acquired due to the structural benefits of the heterojunction. Therefore, the CoSe2/Sb2Se3@C anode affords good cycling stability (264.5 mA h g−1 after 1000 cycles at 2 A g−1) and excellent rate capability (266.0 mA h g−1 at 5 A g−1). This study supplies a reference for developing an advanced anode with multicomponent and heterojunction structures for energy storage. [ABSTRACT FROM AUTHOR]

Vanadium oxides are potential anode materials for sodium-ion batteries, however, their application is limited for their rate capability and cycle life. Herein, hollow spheres of Co-doped V 2 O 3 enveloped in N-doped carbon (Co-V 2 O 3 @NC) are prepared through a hydrothermal step with the following sintering process. The hollow spherical structure supplies short distance and large area for fast ion transfer kinetics, which also provides voids to ease the volume expansion. The strong coupling between Co-V 2 O 3 nanoparticles and carbon layer constitutes a solid structure that enhances the conductivity and keeps electrode integrity. Co-doping introduces plenty of active sites for surface capacitance behavior and accelerates charge transfer. On account of the benefits, Co-V 2 O 3 @NC exhibits excellent Na+ storage properties as anode, including high capacity of 338.5 mAh g−1 at 0.1 A g−1, stable cycling capability of 240 mAh g−1 after 1000 cycles at 1 A g−1, and excellent rate performance. This work describes the importance of constructing specific structured materials for advanced anodes. [Display omitted] • Hollow spheres of Co-doped V 2 O 3 enveloped in N-doped carbon are prepared. • Hollow structure accelerates ion transfer kinetics and buffers volume expansion. • Co-doping provides sites for surface-controlled sodium storage. • Carbon coating improves conductivity and benefits electrode integrity. • High-performance sodium storage performances are acquired. [ABSTRACT FROM AUTHOR]

• Electrochemical activation induces surface reconstruction of CoMo-LDH nanosheets. • The optimized electronic structure and enhanced intrinsic activity are obtained. • The increased catalysis sites and promoted charge transfer are achieved. • Generating 100 mA cm−2 at low overpotentials of 202 mV for HER. Surface reconstruction emerging in the electrochemical oxygen evolution process is regarded to be significantly important for the activated catalysis efficiency, however, which is rarely recognized for hydrogen evolution reaction (HER). Here, the electrochemical activation of CoMo layered double hydroxide (CoMo-LDH) nanosheet arrays is demonstrated to significantly activate the electrochemical HER property. The catalysis performance improvement originates from the surface transformation of CoMo-LDH to Co(OH) 2 /CoOOH, as well as the dissolution of Mo and its adsorption on the catalyst surface in K 2 Mo 3 O 10 phase. Based on the combined benefits of optimized electronic structure, increased catalysis sites, and promoted charge transfer, the overpotentials at catalysis current densities of 10 and 100 mA cm−2 are as low as 113 and 202 mV. This study demonstrates the electrochemical activation strategy to drive the surface reconstruction of bimetal hydroxides for enhanced HER performance, inspiring the research interests on the reconstruction and activation enhancement behaviors of HER electrocatalysts. [ABSTRACT FROM AUTHOR]

• Co-doped Ni 3 S 2 nanosheets assembled flower-like structure is grown on NF. • Co doping brings more active sites and enhanced catalysis kinetics. • Ultrathin nanosheets benefit high surface area and fast charge transfer. • Improved OER performances in alkaline media are achieved. Oxygen evolution reaction (OER) sets the huge obstacle for water electrolysis application, and the low-cost catalysts with small overpotential and fast kinetics are highly needed. Herein, cobalt-doped Ni 3 S 2 nanosheets constructed flower-like architecture is grown on nickel foam (Co-Ni 3 S 2 /NF) toward OER application. It is found that, heteroatom doping induces positive effects for OER, including the modulated electronic structure, more active sites, and accelerated charge transfer. Nanosheets structure assures exposed active sites and shortened charge transfer path. Benefited from the aforementioned advantages, the as-prepared sample exhibits impressive catalysis performances, such as ultralow overpotential of 160 mV at current density of 10 mA cm−2, small Tafel slope of 49 mV dec−1, and high stability, which behaves as the promising catalyst for OER. [ABSTRACT FROM AUTHOR]

Activating carbon materials with superb capacity, kinetics, and stability for sodium storage is desirable for sodium-ion batteries (SIBs), and heteroatom doping is believed as the effective strategy. Herein, ultrafine Co nanoparticles decorated nitrogen-doped carbon is prepared by the pyrolysis of black fungus infiltrated with Co(NO 3) 2 as SIBs anode material. Impressively, Co/NC exhibits efficient sodium storage properties of high specific capacity (345.7 mAh g−1 at 0.1 A g−1), good rate performance (158.2 mAh g−1 at 5 A g−1), and stable cyclic property (218.5 mAh g−1 at 1 A g−1 after 1000 cycles). Incorporation of N and Co produces defects and active sites, causing pseudocapacitive contributed sodium storage behavior with excellent electrochemical kinetics and structure stability. This study provides a reference to prepare high-performance carbon anodes using sustainable biomass materials. [Display omitted] • Co nanoparticles decorated N-doped carbon is prepared as SIBs anode. • Biomass of black fungus infiltrated with Co(NO 3) 2 are used as raw material. • Expanded carbon interlayer is favorable for Na+ insertion. • Pseudocapacitive behavior contributes to fast and large Na+ storage. • Excellent electrochemical Na+ storage performances are achieved. [ABSTRACT FROM AUTHOR]

Heterostructure fabrication is believed to acquire promoted charge transfer and improved surface storage contribution, thus obtaining high-performance anodes for sodium-ion batteries. Herein, the simultaneous phosphatization and selenization of polydopamine functionalized ZIF-67 is adopted to engineer N-doped carbon coated Co(PO 3) 2 /CoSe 2 heterostructure. The hetero-interface with plenty of surface sites is activated with large surface reaction and fast sodium ion transport dynamics. The multiphase synergism and carbon coating layer assure high conductivity and structural stability. The designed sample delivers impressive anode performance, exhibiting a high sodium storage capacity of 333.4 mAh g−1 at 0.1 A g−1 and 192.7 mAh g−1 after 1000 cycles at 2 A g−1. This simple and reasonable method can be utilized to construct other transition metal based heterostructures with multiphase synergism for the application of advanced anodes. [Display omitted] • N-doped carbon coated Co(PO 3) 2 /CoSe 2 heterostructure is prepared. • Heterostrucrue favors surface-controlled pseudocapacitive sodium storage. • N-doped carbon shell enhances conductivity and keeps electrode integrity. • Multiphase synergism benefits electrochemical kinetics and structure stability • Large/fast sodium storage properties with excellent stability are obtained. [ABSTRACT FROM AUTHOR]

Transition metal based materials with hollow structure are considered as advanced electrocatalysts for oxygen evolution reaction (OER). This study reports the NiCo-LDH nanosheets assembled hollow structure arrays on nickel foam, which are synthesized by solvothermal method with ZnCo-MOF nanopolyhedra as precursors. Taking advantage of the nanosheets constructed hollow structure, the obtained sample exhibits good OER catalysis activity with low overpotential of 303 mV at current density of 100 mA cm−2 and satisfied stability. It is demonstrated that Ni2+ and Co2+ are oxidized into Ni3+ and Co3+, which play as robust catalysis sites and greatly promote the catalysis performance for OER. This work demonstrates a promising strategy for controllable preparation of hollow structures of transition metal materials for electrochemical water splitting. NiCo-LDH nanosheets assembled hollow architecture arrays on nickel foam are prepared for advanced OER application due to the structural advantages and the robust active sites of oxidized Ni and Co elements. [Display omitted] • NiCo-LDH nanosheets assembled hollow structure arrays are synthesized. • Structural advantages improve surface area and active sites for OER. • Ni and Co are oxidized to high chemical states to promote OER. • Low overpotential of 303 mV at 100 mA cm−2 is obtained for OER. [ABSTRACT FROM AUTHOR]

• NiFe hydroxide is prepared via ion-assisted method with ZIF-8 as precursor. • Ni 0.75 Fe 0.25 (OH) 2 /NF shows low overpotential of 259 mV at 100 mA cm−2. • The NiFe bimetal effect and nanosheets with oxygen vacancies are key for OER. Developing active water oxidation electrocatalysts with earth-abundant components is significant for bulk hydrogen supply via water electrolysis. Herein, nickel iron hydroxide nanosheets assembled particles on nickel foam are prepared through ion-assisted etching method with ZIF-8 as precursor. The sample achieves remarkable catalysis efficiency toward oxygen evolution reaction with ultralow overpotential of 259 mV at high current density of 100 mA cm−2. The superior catalysis efficiency is assigned to Ni/Fe synergisms of optimized intrinsic activity, abundant surface oxygen vacancies, enhanced charge flow, and increased active sites, as well as nanosheet structure benefits of approachable catalytic sites and shortened charge transform pathways. [ABSTRACT FROM AUTHOR]

• PANI coated Ni 3 Mo 2 P-MoO 3 nanoarrays on nickel foam is prepared. • N species in PANI and metals in NiMoOP form metal-N bonds. • The coupling effect improves the intrinsic OER activity. • Enhanced charge transfer resistance and more active sites are obtained. • High OER activities of 290 and 412 mV at 100 and 400 mA cm−2. To obtain high-efficiency and affordable electrocatalysts for water splitting application, constructing specific nanostructures is believed as an effective solution to pursue advanced structure characteristics for improved catalysis property. In this work, a shell-core structured catalyst of polyaniline coated hybrid Ni 3 Mo 2 P-MoO 3 nanoarrays is designed for oxygen evolution. The polyaniline shell not only assures merit of high conductivity for accelerated charge transfer, but also benefits the catalysis stability. The coupling effect between nitrogen species of polyaniline shell and metals of core materials imparts improved intrinsic catalysis activity and more active sites. Hence, the present sample manifests excellent catalytic efficiency for alkali water oxidation, only needing low overpotentials of 290 and 412 mV at high current densities of 100 and 400 mA cm−2, respectively. The development of shell-core catalyst using polyaniline as shell material paves a way for activating other transition metal catalytic materials and supplies a basis for industrial water splitting applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfur on CoFe alloys embedded in nitrogen-doped carbon nanosheets is designed. • M−S n 2- is the robust catalysis sites for HER. • The synergisms between sulfur and CoFe@NC are beneficial for HER. • 2D NC interacted 3D network supplies easily accessible active sites and rapid charge transfer. • The present S-CoFe@NC exhibits Pt-like HER performance in neutral media. Seeking novel low-cost non-noble metal based electrocatalysts with high efficiency is of great significance to promote industrial application of hydrogen evolution reaction (HER). Herein, we originally demonstrate sulfur on CoFe alloys embedded in nitrogen-doped carbon nanosheets (S-CoFe@NC) catalyst with extremely robust HER activity in neutral media. The present sample exhibits active HER performance with ultralow overpotential of 37 mV at current density of 10 mA cm−2 and Tafel slope of 34 mV dec-1, which is the same as commercial Pt/C. Systemic studies show that strong interaction between bridging S n 2- and CoFe@NC introduces M−S n 2- as the robust catalysis sites for HER, which is also beneficial for the charge exchange. The specific structure of NC nanosheet interconnected network provides structure advantages for easily accessible active sites and fast charge transfer for electrocatalysis. Thus, this work paves a way for the development of new class of sulfur based electrocatalyst with efficient HER performance for neutral water splitting. [ABSTRACT FROM AUTHOR]

• Heterogeneous Co@CoO encapsulated in P, N co-doped carbon fibers is prepared. • Synergism between Co and CoO is beneficial to improve OER. • PNC fiber benefits charge transfer and catalysis stability. • Low overpotentials of 289 (KOH) and 371 (PBS) mV at 10 mA cm−2 for OER. Heterostructured materials favoring synergism, efficient charge transfer, and abundant active sites have aroused enormous interests for water electrolysis. Here heterogeneous Co@CoO encapsulated in P, N co-doped carbon nanofibers supported on carbon cloth (Co@CoO-PNC/CC) has been prepared to pursue attractive synergism for the application of pH-tolerant catalyst for oxygen evolution reaction (OER) in both alkaline and neutral solutions. The prepared Co@CoO-PNC/CC exhibits advanced OER performances, generating a current density of 10 mA cm−2 at overpotential of 289 mV in alkaline media and 371 mV in neutral media. The high OER activity can be assigned to the synergistic effect of abundant active sites and enhanced charge transfer between Co and CoO, as well as the specific P, N co-doped carbon nanofiber architecture. [ABSTRACT FROM AUTHOR]

• S, N co-doped carbon nanosheets are prepared as SIBs anode. • S, N co-doping endows enlarged interlamellar spacing and defective active sites for improved sodium storage. • S, N co-doping improves Na+ diffusion coefficient. • High capacity of 270 mAh g−1 is obtained at 0.1 A g−1 after 100 cycles. • Capacity of 100 mAh g−1 is achieved at high rate of 1 A g−1 after long-term 1000 cycles. Heteroatom doping into specific nanostructure is believed as the leading solution for developing the advanced carbon materials for sodium ion batteries (SIBs), however, the preparation and understanding of heteroatoms co-doped carbon anodes are still challenging. Herein, the sulfur and nitrogen co-doped (weight content of 15.64% for N and 3.1% for S) carbon nanosheets (SNC) are prepared by treating nitrogen-rich carbon nanosheets with sublimation sulfur. The S, N co-doping is responsible for the enlarged interlamellar spacing of 0.38 nm and abundant defect-introduced active sites. These structure features combined with the advantage of nanosheet are significant for activating sodium ion storage properties, endowing SNC with high Na+ storage capacity of 270 mAh g−1 at 0.1 A g−1 and 100 mAh g−1 at 1 A g−1 after 1000 cycles. More importantly, the kinetic analysis is carried out to illustrate that S, N co-doping can improve the Na+ diffusion coefficient in carbon anode and enhance the ion storage. This work deepens the understanding on the boosting effect of heteroatoms dual-doping for the sodium ion storage of carbon materials, which conduces to development of advanced heteroatom doped carbon anodes for SIBs. [ABSTRACT FROM AUTHOR]