MOF derived Co₃O₄nanoparticles embedded in N-doped mesoporous carbon layer/MWCNT hybrids: extraordinary bi-functional electrocatalysts for OER and ORR

Abstract

High efficient and non-precious metal electrocatalysts for oxygen evolution reactions (OER) and oxygen reduction reactions (ORR) are at the heart of key renewable-energy technologies. Nevertheless, developing highly-active bi-functional catalysts at low cost for both OER and ORR still remains a huge challenge. In this paper, Co3O4 nanocrystals embedded in N-doped mesoporous graphitic carbon layer/multiwalled carbon nanotubes (MWCNTs) hybrids are prepared by a facile carbonization and subsequent oxidation process of MWCNTs-based metal-organic framework (MOF). As a result, in alkaline media, the hybrid material catalyzes OER with an onset potential of 1.50 V (vs reversible hydrogen electrode) and over-potential only of 320 mV to achieve a stable current density of 10 mA cm -2 for at least 25 h. The same hybrids also exhibit similar catalytic activity but superior stability to commercial 20 wt% Pt/C catalyst for ORR, making it a high-performance cheap bi-catalyst for both OER and ORR. The design concept of nonmetal-doped and precious-metal-free electrocatalysts from MOF can be extended to fabricate other novel, stable and easy to use catalyst system for advanced applications.

Tunable Bifunctional Activity of MnxCo3−xO4 Nanocrystals Decorated on Carbon Nanotubes for Oxygen Electrocatalysis

“…Therefore, it is of great significance to develop effectivec atalysts from earth-abundant materials. Hence,t ransition-metal/metal oxide nanoparticles andp orous carbon nanostructures have received considerable attention,d ue to their high chemical and thermals tability, and flexibility fort uning of the surfacea nd interface chemistry for the ORR, the OER, or bifunctionality.F or example, attempts have been made in the synthesis of heteroatom-doped carbon nanostructures (graphene, carbon nanotubes (CNTs), and carbon fibers), [6][7][8] metalorganic framework (MOF)-derived metal-NÀCs tructures, [9][10][11] perovskites, [12][13][14][15] and transition-metal oxides (TMOs). [16][17][18][19][20] TMOs, with their multiple oxidation states, show promising surfacea ffinities foro xygen catalysis;t he best examples are cobalto xides.…”

A Novel Metal–Organic Framework Route to Embed Co Nanoparticles into Multi-Walled Carbon Nanotubes for Effective Oxygen Reduction in Alkaline Media

“…Here, J is the current density, J L and J K are the diffusion-and kinetic-limiting current densities, respectively, ω is the angular velocity, F is the Faraday constant (96,485 C mol −1 ), C 0 is the O 2 bulk concentration (C 0 = 1.26 × 10 −6 mol cm −3 ), D 0 is the diffusion coefficient of the O 2 in 0.1 M KOH or HClO 4 (D 0 = 1.9 × 10 −5 cm s −1 ), υ is the kinematic viscosity of the electrolyte (υ = 0.1 m 2 s −1 in 0.1 M KOH or HClO 4 ) [35].…”

Design Strategies toward Advanced MOF‐Derived Electrocatalysts for Energy‐Conversion Reactions

“…Although the metal ions in MOFs are inclined to be reduced to metal NPs during carbonization, it is still likely to convert the metal ions into compounds directly by selecting appropriate precursors and controlling the annealing conditions. [36,42,43,45,73,74,76,[85][86][87][88][89][90][91][92][93][94][95][96][97][98] The most easily obtained compound is transition metal carbides due to the availability of carbon originating from the decomposition of organic ligands. [36,42,43,45,73,74,76,88,93] The case depicted in Figure 1b supports this point.…”

“…For instance, compositing MOF precursors with conductive supports, such as CNTs, [69,95] graphene, [33,34,92] and carbon fabric, [94] has been widely explored to enhance catalytic activity. Recently, Lai et al reported ZIF-8-derived N-enriched meso-microporous carbon (NEMC) frameworks.…”

“…[16] Currently, precious-metal-based catalysts (i.e., Ir, IrO 2 , and RuO 2 ) are the benchmark electrocatalysts for the OER. [15,16] Again, rationally designed materials derived from MOFs have been widely reported as alternative OER electrocatalysts, [35,80,[94][95][96]98,101,[113][114][115][116] and a summary of the OER performances of recent MOF-derived catalysts is listed in Table 2.…”