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Uncontrollable growth of sodium dendrite during repeated sodium plating/stripping process results in low Coulombic efficiency, short cycle life and safety problem of sodium metal batteries. Herein, cobalt-based metal organic frameworks (Co-MOFs) was chosen as precursor, a porous nitrogen-anchored carbon rhombic dodecahedron (CoNC) embedded with Co nanoparticles is designed to uniform Na nucleation and deposition for sodium metal anodes, integrating high surface area and high conductivity. Both DFT calculations and experiment results demonstrate that the CoNC can enhance the sodiophilic for sodium nucleation and deposition, encapsulating sodium into CoNC nanoparticles and realize a dendrite-free Na plating and stripping process. CoNC@Na symmetric cell exhibits stable cycle performance for 1200 ​h ​at 1.0 ​mA ​cm−2 for 1.0 ​mAh cm−2 with low nucleation overpotential. The CoNC@Na half cell can operate stable cycling with a superhigh average Coulombic efficiency of 99.6% for 400 cycles. Moreover, full cell paired with Na3V2(PO4)2F3 (NVPF) cathode exhibits excellent cycling performance with a high reversible specific capacity of 113 ​mAh g−1 and capacity retention of 90%. This offers a sight into the design of electrode for encapsulating sodium into carbon matrix by sodiophilic sites to uniform Na nucleation and growth for dendrite-free Na metal anodes.

Developing active and cost-effective electrocatalysts for hydrogen evolution reaction is greatly desired for growing energy demands. Here, we report a promisingly hierarchical nickel-copper nitride electrode via a simple surface engineering process with a direct growth of copper-based metal-organic frameworks on nickel foam, followed by a low temperature ammonization, as the efficient catalyst for hydrogen evolution reaction. The as-fabricated nickel-copper nitride electrode exhibits a remarkable activity with a lower overpotential of 58 mV for hydrogen evolution reaction at the current density of 10 mA cm −2 , and with strong long-term stability of a negligible morphological changes and potential increases after uninterrupted testing. This work opens a new avenue to design robust and eco-friendly electrocatalyst for hydrogen evolution reaction.

Metal organic frameworks (MOFs) based catalysts are the most promising candidates for electrocatalytic reaction. Herein, we describe a fast, cost-effective and efficient method to construct an oxygen evolution electrocatalyst with a “bivalve hollow nanoellipsoid” structure, namely three dimensional (3D) bi-shells Co9S8/Fe3O4 embedded in S/N co-decorated hollow carbon nanoellipsoid (H-Co9S8/Fe3O4@SNC). The bivalve metallic compounds hollow structure decreases the proton-electron transfer kinetics on carbon nanoellipsoid, and promoting the oxygen evolution reaction (OER). Specifically, the H- Co9S8/Fe3O4@SNC reveals an excellent catalytic activity with a low overpotential of 280 mV at the current density of 10 mA cm−2 and a small Tafel slope of 87 mV dec−1. Moreover, this H-Co9S8/Fe3O4@SNC electrode is applied to rotating ring-disk electrode (RRDE) and show remarkable catalytic stability and give ∼97.5% Faradic efficiency toward OER via chronoamperometric measurement at a rotation rate of 1600 rpm. Following that, the mechanism is investigated and reveal the excellent catalytic activity is mainly owed to the hollow structure and the catalytic synergistic effects of the double shell Co9S8/Fe3O4, simultaneously, the introduction of oxygen vacancy during the pyrolysis process to the formation of Fe3O4.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential to metal-air batteries and fuel cells. Highly efficient and low-cost electrocatalysts for oxygen reactions are in urgent demand. Herein, we synthesized materials through Fe2O3 and NiO depositing on carbon nanotubes (CNTs) by hydrothermal method, which can perform as efficient bifunctional electrocatalysts for the ORR and OER. These catalysts mainly contain macropores which can provide sufficient surface area for active sites. With metal oxides depositing on CNTs, it overcomes some drawbacks such as low conductivity and agglomeration of metal oxides. The catalysts show great electrocatalytic toward ORR and OER even comparing with commercial Pt-C/RuO2 catalysts. Through constructing an air battery and testing the performance of cycling, the stability of the catalyst can also be proved.

Exploiting highly effective and low-cost non-noble metal catalysts for metal/air batteries are still remain a great challenge. In this work, an “active site-framework” structure, namely iron carbide embedded in nitrogen and oxygen co-doped porous carbon framework (A-Fe3C@NO-PC), is successfully synthesized by a polydopamine-protection-assisted pyrolysis strategy. The as-prepared catalyst possesses excellent catalytic activity with a half-wave-potential of 0.85 V (vs. reversible hydrogen electrode) for oxygen reduction reaction. In addition, this A-Fe3C@NO-PC loaded zinc/air battery exhibits a negligible voltage gap increase after 300 continuous cycle tests (52 h) at the current density of 50 mA cm−2. The excellent catalytic performance of the catalyst is contributed to high electronic conductivity of Fe3C, high contents of pyridinic and graphitic-N doped porous carbon framework. The concept and achievement can inspire the development of the surface engineering to design other transition metal species decorated carbon catalysts for metal/air batteries.

Developing efficient and earth-abundant electrocatalysts for electrochemical water splitting is greatly desired due to growing energy demands. Herein, we develop a promising hierarchical nickel-iron-copper nitride electrode that is fabricated via a three-step process, starting with a hydrothermal synthesis of nickel-iron hydroxide on nickel foam and followed by the direct growth of copper metal-organic frameworks and, finally, low temperature ammonization. This approach yields a material that is an efficient catalyst for both the oxygen evolution reaction and the hydrogen evolution reaction. The as-fabricated heterostructured nickel-iron-copper nitride electrode exhibits an excellent activity with an overpotential of only 121 mV for the oxygen evolution reaction and an even a lower overpotential of 33 mV for the hydrogen evolution reaction. Additionally, this structure displays strong long-term stability with only a negligible increase in potential after 500 cycles of uninterrupted cyclic voltammetry testing. To the best of our knowledge, this as-prepared hierarchical nickel-iron-copper nitride is one of the most promising alternatives for the electrochemical oxygen and hydrogen evolution reactions.

Rational design and development of non-precious metal-based electrocatalysts for bifunctional oxygen reduction/evolution reactions (ORR/OER) are essential to realize the dischargeable Zinc-air batteries (ZABs). Herein, for the first time we synthesize CoFe-alloy nanoparticles enveloped by N, P co-doped carbon nanotubes (NPMC/CoFe), through a simple route by pyrolyzing dicyandiamide complex in the presence of phytic acid. The obtained electrocatalysts possess excellent ORR (a half wave potential of 0.896 V in 0.1 M KOH) and OER (η10 mA cm-2 = 310 mV in 1 M KOH) performance, respectively. The liquid-state ZABs based on the NPMC/CoFe air-cathode demonstrates a high peak power density of 146.34 mW cm−2 and excellent durability. Specifically, flexible and button-like ZABs with impressive performances are both realized, which could power light-emitting diodes. This work offers an attractive approach to develop the nonprecious metal-based ORR/OER catalysts, and modulators for the design of performance oriented electrocatalysts for wider electrochemical energy applications.