Nitrogen‐Doped Carbon Nanosheets Encapsulating Cobalt Nanoparticle Hybrids as High‐Performance Bifunctional Electrocatalysts

Abstract

Developing efficient and low‐cost catalysts with excellent catalytic activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of significance for large‐scale commercial applications in rechargeable Zn−air batteries and fuel cells. Herein, we develop a simple, mild and efficient method to synthesize a hybrid of N‐doped carbon nanosheets encapsulating cobalt nanoparticles (Co@NCNSs), which shows favorable catalytic properties toward both ORR and OER with high activity and good stability. The optimized hybrids (Co@NCNSs‐900) exhibit an onset potential of 0.95 V vs. reversible hydrogen electrode (RHE) and a half‐wave potential of 0.85 V vs. RHE for the ORR, and an onset potential of 1.51 V vs. RHE, a potential of 1.59 V vs. RHE at 10 mA cm−2 for the OER, as well as an oxygen electrode activity parameter (ΔE) of 0.802 V in alkaline electrolyte. Moreover, the Zn−air battery with the Co@NCNSs‐900 as the cathode catalyst outperforms that with the commercial Pt/C as cathode catalyst in terms of the maximum power density and stability, showing great prospects in renewable energy applications.

Creating Competitive Active Sites on CNTs Walls by N‐Doping and Sublayer Co4N Encapsulating for Efficient Hydrogen Evolution Reaction

“…The fewer C−O x species may be caused by adsorption of O 2 or H 2 O. In addition, the N 1s segment of N−CNTs@Co 4 N@NF reflects at 398.7 eV, 399.4 eV, 401.1 eV and 403.4 eV, respectively, corresponding to the pyridine N, pyrrolic N/Metal‐N, graphitic N and oxidative N, respectively (Figure c) . This suggests that part of N is doped in carbon nanotubes, while the others bond to metals.…”

FeNi decorated nitrogen-doped hollow carbon spheres as ultra-stable bifunctional oxygen electrocatalyst for rechargeable zinc–air battery with 2.7% decay after 300 hours cycling

“…6,7 Consequently, it is critically important to rationally design and fabricate noble metal-free bifunctional electrocatalysts that exhibit high efficiency and excellent durability. [8][9][10] Over the past decade, many efforts have been devoted to develop non-noble metal bifunctional electrocatalysts, such as oxides, [11][12][13][14] transition metals and their alloys, [15][16][17][18] sulphides, 19 nitrides, 20,21 and various carbon materials. 22,23 Among these, the transition metal-nitrogen/carbon compound oen exhibited excellent electrocatalytic activity and long-term stability for OER/ ORR.…”

Engineering Active Sites in Three‐Dimensional Hierarchically Porous Graphene‐Like Carbon with Co and N‐Doped Carbon for High‐Performance Zinc‐Air Battery

“…[7,11] Recent studies reveal that the coupling of Co nanoparticles with heteroatom doped carbon, especially, N-doped carbon (NC) materials can, because of the improved electron transfer at the interface between Co and NC, lead to satisfactory ORR and OER in terms of both high positive onset potential and high current density. [6,7,10,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, most synthesis methods of Co-NCbased catalysts involve the uncontrolled pyrolysis of metalorganic framework, which results in low surface area and nonhomogeneous distribution of active sites, thereby decreasing the active sites accessibility in electrocatalysis. Therefore, to accelerate the overall kinetics of oxygen electrocatalysis, it is necessary to design a high-performance Co-NC-based electrocatalyst by nanoengineering of the surface of the catalyst with metallic Co and non-metallic N, controlled interface layer construction, and surface area enhancement, which can maximize the accessibility of the active sites.…”