3D Hierarchically Porous Graphitic Carbon Nitride Modified Graphene‐Pt Hybrid as Efficient Methanol Oxidation Catalysts

Abstract

reducing the amount of Pt, for example, to construct hybrids electrode materials incorporating Pt-based nanocatalysts into carbon support materials, such as porous carbons, [5] carbon nanotubes (CNT), [6,7] and graphene sheets. [8] To improve the surface of chemically inert carbon materials as well as to introduce microspores, several different strategies have been investigated. A useful strategy is chemical activation by using alkali hydroxides as activating agents for pulling in microspores with narrow distribution and increasing their surface areas. [9] Another efficient strategy is heteroatom doping. Recent studies have demonstrated that it is conductive to modulate the electronic structures and chemical reactivity of carbon materials, resulting in the remarkably enhanced catalytic ability. [10] To date, a variety of heteroatom-doped carbon materials and carbon-based hybrids have been developed, such as nitrogen, phosphorus, or boron-doped carbon black, [11] carbon nanotubes, [12] or graphene, [13] nitrogen and sulfur-codoped graphene, [14] and carbon nitride-graphene hybrids. [15][16][17] It is noteworthy that incorporation of heteroatoms into the frameworks of carbon materials can help to remove the absorbed poisoning intermediates, thus ensuring the high exposure of the active sites and promoting the catalytic reaction. [18,19] In particular, graphitic carbon nitride (g-C 3 N 4 ), as a typical nitrogen-rich carbon materials, has become a hot topic of interest due to its remarkable properties including ideal 2D structure, ultrahigh nitrogen content, excellent chemical and thermal stability, which can be applied in a wide range of areas such as metalfree catalysts for water splitting, [20] CO 2 fixation, [21] organic pollutant degradation, [22] and so on.On the other hand, nanostructured materials with hierarchically multimodal pore-size distributions have become a hot topic of interest in the catalytic community owing to that they combine the micro and mesoporosity with the macroporous networks. [23] Rich mesoporosity brings large specific surface areas and the robust macropores lead to accessible diffusion pathways. 3D graphene-based frameworks, such as hydrogel, [24] aerogels, [25,26] foams, [27] and sponges, [28] are an important class of new-generation template-free hierarchically porous materials. 3D graphene-based materials are probably upgraded by the recognition that their high specific surface area and intimate A 3D hierarchically porous carbon nanocomposite constituting of graphitic carbon nitride (g-C 3 N 4 ) chemically integrated with reduced graphene oxide (rGO) via covalent CN bonds is reported. This porous nanocomposite has high nitrogen content, large surface area, interconnected porous networks, and good electrical conductivity, and is used to load Pt nanoparticles to form 3D Pt-g-C 3 N 4 -rGO catalyst for direct methanol fuel cell anode. The catalyst shows an unusual electrocatalytic ability toward methanol electrooxidation, such as high activity, intriguing poison tolerance, and rel...

The Pt/g-C3N4-CNS catalyst via in situ synthesis process with excellent performance for methanol electrocatalytic oxidation reaction

“…Zhang et al used C-N covalent bonds to combine g-C 3 N 4 and reduced graphene oxide into three-dimensional porous carbon nanocomposite carriers for loading Pt nanoparticles to form 3D Pt-g-C 3 N 4 -rGO and exhibit excellent methanol electrocatalytic performance. 24,25 Zhong et al synthesized Mn-Fe@g-C 3 N 4 by the in situ wrapping of g-C 3 N 4 on MIL-101(Fe) and showed excellent initial potential and half-wave potential of the reduction-oxidation reaction. 26 Li et al first proposed the preparation of g-C 3 N 4 -coated carbon black composite as a carrier for the electrocatalytic oxidation reaction of methanol and found that the catalytic activity was 2.1 times that of pure carbon black carrier.…”

Nitrogen‐Doped Hierarchical Porous Carbon Architecture Incorporated with Cobalt Nanoparticles and Carbon Nanotubes as Efficient Electrocatalyst for Oxygen Reduction Reaction

“…A 3D hierarchical porous structure has been regarded as one of the most promising electrocatalysts and electrocatalyst supports. The micropores and mesopores could increase the active sites, and the macropores could promote the mass transport toward and away from the active sites . To date, the common routes for fabricating hierarchical carbon structures typically involve templates, such as porous alumina, silica, zeolite, and polystyrene .…”

Molecular Trapping Strategy To Stabilize Subnanometric Pt Clusters for Highly Active Electrocatalysis

“…Heterogeneous catalysis is a surface process involving most, if not all, constitutional atoms at or near the catalyst surface. − For noble metal catalysts, the nanostructures of metal clusters with dimensions in the range of a single metal atom to the nanoparticles (>2 nm) have gained great interest in order to lower the cost of the catalysts and exploit efficient use of catalytically active components. , For instance, Pt-based catalysts possess unique and significant electrocatalytic activities toward methanol oxidation reactions, but the high costs and the scarcity of Pt sources seriously block their large-scale commercial applications. , Small nanoclusters are therefore extremely desirable in improving Pt utilization efficiency. Generally, the size of metal clusters is also one of the most critical factors that dictate the performances of a catalyst .…”

“…The material, in fact, contains periodic tri- s -triazine subunits coupled via the planar tertiary amino groups, resulting in uniform structural N-coordinating cavities. − The high level of pyridinic nitrogen in each cavity is capable of tenaciously capturing metal ions owing to the nature of abundant electron lone pairs. − Such strong electronic interactions have extensively been regarded as a crucial tool to manipulate the electronic structures of the metal nanoclusters and thus to interact with the intermediates during the catalytic reactions. , More importantly, g-C 3 N 4 offers abundant and homogeneous nitrogen coordinators, which gives rise to many inherent advantages, including sustaining metal atoms with their neutral states, efficiently accumulating surface polarization charges on metal atoms, , and affording more accurate information for the identification of catalytically active sites. ,, Unfortunately, its low electrical conductivity dramatically deteriorates the electrocatalytic processes, limiting their applications in the field of electrochemistry. Tremendous efforts have been made in exploring effective strategies to improve its electron transferability, such as designing advanced nanostructures, , incorporating mesoporous structures, , combining with carbon materials, ,− and heteroatom doping. , However, developing a strongly coupled g-C 3 N 4 -based composite support with fast electron mobility, robust structural stability, and mechanical strength is still highly desirable.…”

“…However, the adsorbed CO ad scarcely strips out until the oxygen-containing groups, that is, −OH, are produced on the Pt surface under high potentials. Considering that the g-C 3 N 4 , as one kind of metal-free catalyst, possesses efficient catalytic activities toward water splitting reactions, the incorporation of the g-C 3 N 4 could accelerate the formation of adsorbed −OH species at a low electrode potential, , thus promoting the process of oxidative removal of the adsorbed CO ad . This process makes the Pt sites with less accumulation of CO ad , which results in less CO ad poisoning and assures sufficient catalytically active sites toward the accession for the reactants.…”