3D self-assembly of ultrafine molybdenum carbide confined in N-doped carbon nanosheets for efficient hydrogen production

Abstract

Electrochemical water splitting has been intensively pursued as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of low-cost and high-performance electrocatalysts for the hydrogen evolution reaction (HER) hinders the large-scale application. Herein, we have rationally designed and synthesized 3D self-assembly architectures assembled from ultrafine MoC nanoparticles (0D) uniformly embedded within N-doped carbon nanosheets (2D) for the HER via a simple protocol. The well-organized 3D nanostructures are composed of very small MoC nanocrystallites (<2 nm) and free-stretching conductive carbon nanosheets with high specific surface areas and abundant mesopores, which can expose more active sites and facilitate electron/ion transport pathways. Based on the merits of the composition and configuration, the resultant hierarchical 3D self-assembly architectures exhibit remarkable electrocatalytic performance and stability for the HER.

Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn–Air Battery and Water Electrocatalysis

“…In the Mo 3d region (Figure c), the XPS signal fitting reveals the existence of four oxidation states (i.e., +2, +3, +4, and +6) for the Mo element. The Mo 4+ at 229.8 and 233.7 eV and Mo 6+ at 232.8 and 235.6 eV can be attributable to the surface oxidation product of MoO 2 and MoO 3 that are readily contaminated in air, consistent with previous reports. , The remaining two oxidation states that are located at 228.1/231.7 and 228.7/232.1 eV can be reasonably assigned to the Mo 2+ and Mo 3+ species, respectively . As depicted in Figure d, the signals positioned in Co 2p 3/2 and Co 2p 1/2 regions at 778.7/794.1, 780.7/796.1, 782.2/797.1, and 785.2/803.3 eV can be easily determined, corresponding well to the expected metallic Co, oxidized Co, Co–N structures, and Co satellite peaks, respectively .…”

“…Figure e exhibits four major subunits with binding energies at 284.5, 285.2, 286.1, and 288.3 eV, which can be indexed to Mo–C, CC/C–C, C–O/CN, and C–N/CO, respectively . The N 1s spectrum shown in Figure f displays five fitted signals, where the peaks at 398.5 and 399.3 eV may be associated with the P6–N (pyridinic-N, 31.34%) and Co–N (25.09%), respectively, which further proves the formation of Co–N species in the sample. , The XPS bands located at 400.5, 401.1, and 402.8 eV correspond to the presence of P5–N (pyrrolic-N, 19.57%), G6–N (graphitic-N, 18.23%), and oxygenated N (5.67%), respectively. Obviously, the doped N is present in diverse chemical environments in the catalyst material.…”

“…The Mo 4+ at 229.8 and 233.7 eV and Mo 6+ at 232.8 and 235.6 eV can be attributable to the surface oxidation product of MoO 2 and MoO 3 that are readily contaminated in air, consistent with previous reports. 32,47 The 49 Among these, the resulting Co−N structures are generally considered to be the active sites for the ORR, thus contributing to high electrocatalytic performance. 49 The resulting N and C elements arise from the pyrolysis of PDA coating and organic linker in ZIF-67.…”

Hollow Hemispherical Carbon Microspheres with Mo2C Nanoparticles Synthesized by Precursor Design: Effective Noble Metal‐Free Catalysts for Dehydrogenation

“…[27] Another feasible synthetic strategy entails the use of various support materials to anchor and stabilize small metal carbide nanoparticles. This can be achieved, for example, by conjugating Mo-based compounds onto carbon support materials, such as onion-shaped carbons, [28] carbon nanofibers, [29] carbon nanotubes, [30] carbon nanoribbons, [9] and carbon nanosheets (graphene), [31,32] and then transforming the Mo species into Mo x C in situ. Similar materials can also be made by directly pyrolyzing metal-organic frameworks (MOFs).…”

Submicron Co9S8/CoS/Carbon Spheres Derived from Bacteria for the Electrocatalytic Oxygen Reduction Reaction

“…In addition, with the fast development of micro/nanotechnology, catalysts are usually prepared into micro/nano‐architectures with high accessible surface area to further promote the electrocatalytic efficiency. Different synthesis methods, such as hydrothermal, chemical vapor deposition, electrodeposition, self‐assembly, sol‐gel method, etc ., have been used to obtain materials with different morphologies. However, confined by the synthesizing mechanism and physicochemical properties of reactants, each of these methods can only obtain limited kinds of structures.…”