A metal–organic framework route to in situ encapsulation of Co@Co₃O₄@C core@bishell nanoparticles into a highly ordered porous carbon matrix for oxygen reduction

Abstract

Rational design of non-noble metal catalysts with the electrocatalytic activity comparable or even superior to Pt is extremely important for the future fuel cell-based renewable energy device. Herein, we demonstrate a new concept that metal-organic framework (MOF) can be used as a novel precursor to insitu encapsulate Co@Co 3 O 4 @C core@bishell nanoparticles (NPs) into a highly ordered porous carbon 10 matrix (CM) (denoted as Co@Co 3 O 4 @C-CM). The central cobalt ions from MOF are used as metal source to produce Co metal cores, which are later transformed into fancy Co@Co 3 O 4 nanostructure via a controlled oxidation. The most notable feature of our Co@Co 3 O 4 @C-CM is that the highly ordered CM can provide much better transport pathway than the disordered pure MOF derived nanostructure that can facilitate the mass transport of O 2 and electrolyte. As a result, the well-designed Co@Co 3 O 4 @C-CM 15 derived from MOF shows almost identical activity but superior stability and methanol tolerance for ORR relatively to the commercial Pt/C in alkaline medium. Our work first reports the novel Co@Co 3 O 4 @C nanostructure from MOF and also reveals the important role of the introduction of highly ordered carbon matrix into MOF derived catalyst on enhancing the ORR activity and stability. To the best of our knowledge, Co@Co 3 O 4 @C-CM is the most efficient non-noble metal nanocatalyst ever reported for 20 ORR. 65 (denoted as Co@Co 3 O 4 @C-CM), which is very different from the preparation of traditional nanocatalysts directly derived from MOFs. The central cobalt ions from MOFs were used as metal source to produce Co metal cores, which were later transformed into Co@Co 3 O 4 NPs via a simple oxidation process. Co 3 O 4 has 70

Recent Progress on MOF-Derived Nanomaterials as Advanced Electrocatalysts in Fuel Cells

“…To date, carbon-supported Co/Co 3 O 4 is one of the most extensively studied catalysts for oxygen reduction in fuel cells [58,[62][63][64]. In 2014, Li and co-workers [55] proposed the application of Co-based MOFs (ZIF-67) as the precursor for fabricating the nanoporous Co-Nx-C hybrid, which can be used as an efficient ORR catalyst in both alkaline and acidic electrolyte.…”

“…To pursue advanced ORR catalysts, the properties of more exposed active sites and accessible surface area for rapid mass transport should be a research priority. Recently, Guo and co-workers demonstrated a new concept allowing ZIF-9 (synthesized from Co 2+ and benzimidazole) to be used as a novel precursor for the in situ encapsulation of Co@Co 3 O 4 @C core@bishell nanoparticles into a highly ordered porous carbon matrix (CM) (denoted as Co@Co 3 O 4 @C-CM) [58]. The central cobalt ions in the ZIF-9-CM precursor are transformed into a fancy Co@Co 3 O 4 core-shell nanostructure during a controlled oxidation process.…”

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

“…[58,60] For instance, in order to fabricate N-doped MOF-derived materials, zeolitic imiazolate frameworks (ZIFs), a subclass of MOFs composed of tetrahedrally coordinated transition metal ions (e.g., Zn, Fe, Co, Cu) and imidazolate (IM) ligands, are frequently utilized as the precursor and/or template because of their high N content and other preferred properties, such as large surface area and uniform particle size. [24,33,34,36,[38][39][40][41]44,53,[64][65][66][67][68][69] Recently, You et al reported the conversion of ZIF-67 (Co(MIM) 2 , MIM = methylimidazole) to Co-and N-doped carbon (CoNC) via direct pyrolysis, producing a N-doped material with high N content. [39] Similarly, Chen and co-workers studied porous carbon materials derived from a series of bimetallic ZIFs (BMZIFs), which are based on ZIF-8 and ZIF-67 with varied Zn/Co ratio.…”

“…[40,53,64,68,70,77,80] Since the metal ions distribute homogeneously among the framework, most of the generated transition metal NPs are encapsulated by the carbon materials. According to previous literature, metal NPs alone display minimal electrocatalytic activity toward energy-conversion reactions.…”

“…As an important alternative to Pt catalysts, MOF-derived materials exhibit remarkable ORR performance in terms of activity, durability, and tolerance to methanol. [24,[32][33][34][38][39][40][41][42][43][44]47,53,[58][59][60][61][62][63][65][66][67][68][69][70][71][72][73][75][76][77]81,83,97,99,[107][108][109] In particular, some newly developed MOF derivatives achieved highly improved activity that is comparable and even superior to Pt catalysts under identical experimental conditions. Table 1 summarizes the catalytic performances of representative MOF-derived electrocatalysts for the ORR.…”