Designing a highly active electrocatalyst with optimal stability at low cost is must and non-negotiable if large-scale implementations of fuel cells are to be fully realized. Zeolitic-imidazolate frameworks (ZIFs) offer rich platforms to design multifunctional materials due to their flexibility and ultrahigh surface area. Herein, an advanced Co-N x /C nanorod array derived from 3D ZIF nanocrystals with superior electrocatalytic activity and stability toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) compared to commercial Pt/C and IrO 2 , respectively, is synthesized. Remarkably, as a bifunctional catalyst (E j = 10 (OER) − E 1/2 (ORR) ≈ 0.65 V), it further displays high performance of Zn-air batteries with high cycling stability even at a high current density. Such supercatalytic properties are largely attributed to the synergistic effect of the chemical composition, high surface area, and abundant active sites of the nanorods. The activity origin is clarified through post oxygen reduction X-ray photoelectron spectroscopy analysis and density functional theory studies. Undoubtedly, this approach opens a new avenue to strategically design highly active and performance-oriented electrocatalytic materials for wider electrochemical energy applications.

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However, the limited lithium resource in earth is detrimental to the further application due to the possible increasing cost and unstable energy supply. [12][13][14][15] Therefore, there is an urgent demand for developing alternative energy storage devices with low cost while maintaining a comparable performance to LIBs. Among them, sodium-ion batteries (SIBs) have become the worldwide focus owing to abundant resources and low cost. [16][17][18][19] To develop high-performance SIBs, it remains challenging to discover/develop suitable electrode materials (especially cathode) to satisfy the requirement of long-term cycling stability and rate-capability.Owing to larger radius of Na + than that of Li + (0.98 vs 0.69 Å), various cathode materials with large open frameworks, including layered transitionmetal oxides [19][20][21][22][23][24][25] and polyanionic compounds, [2,13,18,[26][27][28][29][30][31][32][33] have been developed for (1) the improved sodium storage capacity, (2) the facilitated Na + diffusion in the lattice, and (3) the restricted structure degradation caused by Na + insertion/extraction. The NASICON (sodium (Na) super ion conductor) Na x M 2 (NO 4 ) 3 (M = transition metal, N = P 5+ , Si 4+ , S 6+ , and Mo 6+ ) structure with 3D large open framework allows for rapid and reversible ion diffusion in the lattice, which is now developed as electrode with promising electrochemical performance. [34] Among these, the Na 3 V 2 (PO 4 ) 3 (NVP) becomes a "shining star" with high sodium diffusion ability and remarkable high energy density (i.e., 400 Wh kg −1 ). [18] However, the high ionic diffusion ability of NVP is accompanied with poor electronic conductivity, [35] which results in the low utilization of active materials even at low rates. In order to obtain remarkable performance of NVP, the hurdles of poor rate capability and cycling stability need to be further addressed. Recently, carbon-coated active nanocrystals embedded in a porous carbon matrix, which demonstrated excellent rate performance and cycling stability for Li 3 V 2 (PO 4 ) 3 cathodes, [36,37] as well as for NVP cathodes. [38][39][40] In general, the porous carbon content is usually high, which may lead to the decrease of tap density and entire cell volumetric energy density. [41,42] Li and co-workers reported adaptive graphene gel films as a highly compact electrode with Na 3 V 2 (PO 4 ) 3 (NVP) is regarded as a promising cathode for advanced sodiumion batteries (SIBs) due to its high theoretical capacity and stable sodium (Na) super ion conductor (NASICON) structure. However, strongly impeded by its low electronic conductivity, the general NVP delivers undesirable rate capacity and fails to meet the demands for quick charge. Herein, a novel and facile synthesis of layer-by-layer NVP@reduced graphene oxide (rGO) nanocomposite is presented through modifying the surface charge of NVP gel precursor. The well-designed layered NVP@rGO with confined NVP nanocrystal in between rGO layers offers high electronic and ionic conductivity as well as sta...