Search

Molybdenum carbide is one of non‐precious metal materials and it is a promising electrocatalyst for hydrogen production. Synthesis and improvement of molybdenum carbide's catalytic performance is of great significance. Herein, carbon‐based Mo2C with hybrid phase of MoO2 was fabricated by matching the composition of Mo and C derived from pomelo peel and optimizing raw carbon amount and prolysis temperature. The resulting MoO2/Mo2C@C is composed of loose microspheres with mesoporous microstructure and is self‐assembled from nanoparticles. The results show that MoO2/Mo2C@C2 material exhibits excellent HER performance and only a low overpotentials of 143 mV is needed to drive the current density of 10 mA cm−2 in alkaline solution, and Tafel slopes are only 63.4 mV dec−1, respectively. Notably, it has potential application at low overpotentials to drive large current density and this strategy also provides a universal route to prepare non‐noble metal catalyst with hybrid phase of oxide/carbide. [ABSTRACT FROM AUTHOR]

As a non-noble metal material, molybdenum carbide is considered to be an electrocatalyst with the most potential for the hydrogen evolution reaction (HER) due to its similar electron structure to platinum. However, its high preparation temperature easily leads to aggregations of nanoparticles (NPs) that affect the properties of Mo2C. For this purpose, we synthesized ultrafine molybdenum carbide anchored on nanocarbon (MCC) by designing an Mo-precursor to engineer micro/nanostructures. The results show that as-prepared MCC materials consist of 3D laminated 2D lamellar structures that are self-assembled from Mo2C NPs anchored on nanocarbon. Electrocatalytic tests indicate that the 3D/2D MCC materials exhibit excellent activity and stability in alkaline solution. Notably, a low overpotential of 123 mV is achieved to drive a current density of 10 mA cm−2 for HER, which implies the 3D/2D structures are conducive to molecules accessing active sites, transport and diffusion, and this structural MCC has promising application as an alternative non-noble metal electrocatalyst for hydrogen evolution and other catalysis. [ABSTRACT FROM AUTHOR]

Mo2C is one of the promising alternatives to the precious metal catalyst for hydrogen evolution reaction (HER). However, it is still challenging to prepare highly dispersed Mo2C and prevent nanoparticles (NPs) from sintering during high‐temperature carbonization. Herein, a strategy is proposed to realize dual purposes that confine the coalescence of Mo2C NPs and redistribute charge density by regulating N‐doped contents. As‐synthesized molybdenum carbide nanodots are well dispersed on the N‐doped carbon nanolayers, and the size of Mo2C is uniform and less than 5 nm. The HER tests reveal that as‐prepared Mo2C nanodots exhibit excellent electrocatalytic activity for HER and long‐term stability. Theory calculation proves that optimizing N doping amount can tune hydrogen adsorption free energies and redistribute charge density. The present study provides insight into the impact of nitrogen doped in C/Mo2C and also a synthetic route to achieve heteroatom doping and size control for the synthesis of nanocatalysts beyond Mo2C. [ABSTRACT FROM AUTHOR]

The production of hydrogen via electrochemical water splitting has the potential to enable the utilization of hydrogen‐powered fuel cells on a large scale. However, to realize this technology, inexpensive, noble metal‐free electrocatalysts possessing high performances for the hydrogen evolution reaction (HER) are needed. Mo2C nanoparticles recently receive much attention as alternative noble metal‐free electrocatalysts because their electronic structures are akin to that of Pt. However, the synthesis of Mo2C at nanoscale with high catalytic activity for HER remains a great challenge. Moreover, although efforts have been made to prevent their aggregation, the particles coalesce during high temperature carbonization, which is typically used to produce such transition metal carbides. Here, the synthesis of Mo2C nanodots that are well‐dispersed within 3D cage‐like carbon microparticles using rationally designed Mo‐based xerogels, which are prepared via the sol–gel process as precursors, is reported. During their pyrolysis, the xerogels maintain their structures while the Mo species in them transform into well‐dispersed Mo2C nanodots in situ. The as‐synthesized Mo2C nanodots exhibit excellent electrocatalytic activity for HER, in both alkaline and acidic media, while remaining largely stable. The work also demonstrates a promising synthetic route and procedure to other well‐dispersed yet stable nanocatalysts. [ABSTRACT FROM AUTHOR]

Molybdenum carbide possessing a Pt‐like d‐band electronic structure is considered as one of potential candidates of electrocatalysts and it shows intrinsic catalytic property. However, a high carbonizing temperature easily leads to the coalescence of nanoparticles (NPs). Here, we propose a simple sol‐gel route to achieve high dispersity of carbide NPs by designing a Mo‐involved xerogel. The results show that molybdenum carbide NPs are dispersed and anchored on the nitrogen‐doped carbon nanosheets (Mo2C@NC). Ultrathin carbon layers resemble graphene and the network structures act as a support of carbide NPs, which can hinder NPs' coalescence effectively. Nanpoparticles cross‐coupled on network‐structure nanosheets display the grid shapes. Electrochemical studies indicate that Mo2C@NC material exhibits outstanding hydrogen evolution performance in alkaline electrolyte. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting has been considered as a promising method for large‐scale hydrogen production. However, the development of high‐performance and low‐cost noble metal‐free electrocatalysts for hydrogen evolution reaction (HER) remains a great challenge. Transition metal carbides (such as molybdenum carbide) are one of the most potential substitutes for noble metal as electrocatalysts for HER. One of the effective measures for further enhancing their performances is to hinder the coalescence of nanoparticles. Here we demonstrate a two‐dimensional ultrafine molybdenum carbide‐coupled mesoporous structured meshlike carbon nanolayers synthesized vis facile route based on holes in the carbon nanolayer structures blocking nanoparticle agglomeration. Molybdenum carbide clusters dispersed on the carbon nanolayers are successfully prepared by carbonization of molybdate‐polyvinylpyrrolidone precursor as a proof of concept, which exhibits excellent electrocatalytic activity for the HER and high stability in basic medium. The present study provides some references for the design and synthesis of nanostructured electrocatalysts utilizing 2D meshlike materials to prevent nanoparticles from agglomerating. [ABSTRACT FROM AUTHOR]

Transition metal carbide such as molybdenum carbide has been widely used in electrolytic water for hydrogen production due to its potential catalytic property. The synthesis of molybdenum carbide-based high-efficient catalysts by simple process remains great challenges. Herein, Mo oxide/carbide material with hybrid morphology was synthesized by carbonizing mixture of lotus roots and Mo salt. The as-obtained material consists of MoO 2 /Mo 2 C (MOMC) anchored on biomass-derived nitrogen-doped carbon (NC) matrix. The results show that as-prepared material displays leaf-like and belt-like nanosheets, and the MOMC/NC catalyst with optimal Mo contents exhibits an excellent activity with a low overpotential of 138 mV to drive 10 mA cm−2 and Tafel slope is 56.7 mV dec−1 in alkaline medium, indicating that as-prepared catalyst will have promising application in the field of catalysis. [Display omitted] • Ultrasmall MoO 2 /Mo 2 C NPs were synthesized by carbonizing lotus roots and Mo salt. • Biomass-derived carbon consists of leaf-like and belt-like nanosheets. • The as-obtained MoO 2 /Mo 2 C/C exhibited superior electrocatalytic activity and stability for HER. • As-synthesized material is a promising noble metal-free electrocatalyst served as HER. [ABSTRACT FROM AUTHOR]

Production of hydrogen from electrochemical water splitting has been regarded as one of the most economic and sustainable techniques for green fuel production. It is significant and challengeable to develop highly efficient and low cost noble metal-free electrocatalysts. Presently, molybdenum-based electrocatalysts were regarded as potential alternatives for the hydrogen evolution reaction (HER). Here, the well-dispersed and ultrasmall Mo 2 C nanoparticles (NPs) anchored on 2D carbon nanosheets were synthesized by designing chelate precursor and following pyrolysis, which was proved to be an effective approach for preparing carbon-loaded Mo 2 C NPs. The as-obtained Mo 2 C/C material exhibits an outstanding activity and stability in hydrogen evolution reaction (HER). It needs an overpotential of 147 mV to drive 10 mA cm−2 and Tafel slope is 64.2 mV dec−1 in alkaline medium, implying that Mo 2 C/C material will be a potential noble metal-free electrocatalyst for HER. The design of Mo-chelate precursor is a feasible route to synthesize ultrafine Mo 2 C and it can provide a reference for synthesizing other nanoparticles and hindering particle coalescence at high preparation temperature. • Ultrasmall Mo 2 C nanoparticles coupled with nanocarbon matrix material (MC/C) was synthesized by a facile sol-gel approach. • The size distribution of Mo 2 C is in the range of 2.8–6.2 nm and the mean particle sizes is about 4.3 nm. • The MC/C-6 electrocatalyst exhibited superior electrocatalytic activity and stability for the HER. • New catalyst material has promising application in electrocatalysis. [ABSTRACT FROM AUTHOR]