Cobalt‐Embedded N‐Doped Carbon Arrays Derived In Situ as Trifunctional Catalyst Toward Hydrogen and Oxygen Evolution, and Oxygen Reduction

Abstract

The carbons containing metals coordinated with nitrogen are emerging as the most promising catalysts toward various heterogeneous catalyses. In this paper, such a carbon catalyst is prepared through a chemical vapor deposition (CVD)‐supported precursor pyrolysis. Compared with the direct pyrolysis of polypyrrole@cobalt salt precursor, the incorporation of dicyanodiamide as the CVD source facilitates the diversification and hierarchization of carbon morphology, the reduction of Co particle size, and the increase of the proportion of interfacial Co−N−C and pyridinic‐N. The catalyst is composed of in‐situ‐grown multiple‐morphology carbons (MMCs) with metallic Co particles embedded, where the MMCs are a combination of nano‐particles, ‐rods, and ‐wires, all comprised by small N‐doped carbon nanoflakes. Owing to the combined modulation on morphology configurations and defect states, the Co/MMCs catalyst demonstrates excellent activities toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). A half‐wave potential of 0.84 V and low overpotentials of 86 and 180 mV at 10 mA cm−2 current density for HER and OER are achieved, respectively. Additionally, the catalyst also demonstrates favorable prospects for large‐scale applications in overall water splitting and Zn‐air battery.

Solvent‐Free Chemical Approach to Synthesize Co Nanoparticles Supported on N‐doped Porous Carbon for Efficient Electrocatalytic Oxygen Reduction

“…The relatively low Co content may be due to the inability to detect cobalt nanoparticles encapsulated by graphitized carbon layer, which conformed to the XRD results. From the XPS spectrum of Co 2p (Figure d, S7), the peaks located at 780.2 eV and 796.2 eV were assigned to Co−O y phase, while the peak of 781.7 eV could be appointed to Co−N phase . In addition, the peaks of 779.2 eV and 793.5 eV indicate the presence of zero‐valence state of metal Co, while the presence of Co−O y phase was mainly due to the oxidation caused by the environment around the surface of Co nanoparticles.…”

Recent Advances on Self‐Supported Arrayed Bifunctional Oxygen Electrocatalysts for Flexible Solid‐State Zn–Air Batteries

“…Among all the transition metal elements, cobalt is the hottest choice, which proves to be highly active in both OER and ORR. [ 60,97,98 ] Zeolitic‐imidazolate frameworks (ZIFs) derived carbon materials are widely used as supports due to their high surface area, rich porosity, and uniformly distributed metal nodes. Through a pyrolysis and/or ion exchange process, ZIFs are converted to metal/nitrogen‐doped carbon frameworks.…”

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

“…As a bifunctional ORR/OER electrocatalyst, Co-NC/3DHPGC exhibits a ΔE value of 0.78 V (Figure 4c), which is not only lower than that of all the other electrocatalysts (ΔE Co/3DHPGC = 0.95 V, ΔE Pt/C = 0.97 V, and ΔE RuO2 = 1.24 V) tested here but also comparable to or even lower than that of the most active Co-NC-based bifunctional electrocatalysts reported so far in the literature (Table S1). The excellent bifunctional oxygen electrocatalytic activity of Co-NC/ 3DHPGC can be ascribed to several factors: 1) formation of Co-NC active sites, which are known as highly active for ORR; [12][13][14][15][16][17][18][19][20][21][22][23][24] 2) accessibility of active sites through mesopores of 3DHPGC and thin layer of NC; [27,41] and 3) formation of graphitic carbon layer on Co, which facilitates electron transfer at interface. [10]…”

“…[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.…”