Molybdenum carbide materials are considered to be promising hydrogen evolution reaction (HER) electrocatalysts due to their similar electronic structures and catalytic activities to Pt-based catalysts. Here, we report a facile synthesis of β-Mo2C nanoparticles supported on nitrogen-doped carbon nanotubes (Mo2C/N–C) through a one-step carbonization of Mo-containing anion-doped polyaniline nanotubes. It has been revealed that the size of the obtained Mo2C nanoparticles can be effectively tuned by applying different Mo-containing anions. With MoO42– from Na2MoO4, the as-prepared Mo2C/N–C(S) with ultrasmall (2–3 nm) Mo2C nanoparticles shows excellent electrocatalytic HER activity in acidic media, with an overpotential of 189 mV vs reversible hydrogen electrode (RHE) at a geometric current density of −10 mA cm–2 and a Tafel slope of 58 mV dec–1. This study opens up a new avenue for the size-controllable synthesis of transition metal carbide nanoparticles loaded on carbon supports for energy conversion applications.
Molybdenum carbide catalysts over activated carbon with different crystal phases were synthesized under controllable carburization atmospheres and temperatures for transfer hydrogenation of Kraft lignin in ethanol to aromatic monomers. Single α-MoC1–x and crystal transformation of α-MoC1–x to β-Mo2C are observed under a CH4/H2 mixture and H2 carburization atmospheres, respectively. The mixed crystal phases of α-MoC1–x and β-Mo2C with different crystallinities under a N2 carburization atmosphere exhibit higher activity with a maximum aromatic yield of 0.5163 g/g Kraft lignin when carburized at 700 °C. The dehydrogenation reaction and Kraft lignin hydrogenation are proposed to explain the synergistic effect of β-Mo2C, base, and α-MoC1–x for the base-promoted transfer hydrogenation process in ethanol, which is confirmed by in situ Fourier transform infrared analysis. This highly efficient process is suitable for the conversion of different lignin feedstock.
The present work effectively achieved the production of a self-supporting electrode with high efficiency. The process involves incorporating nickel and molybdenum carbide (Mo 2 C) phases within the channels of wood through high-temperature calcination at the nanoscale. The obtained carbonized wood (CW) possesses low tortuosity and three-dimensional vertical channels, providing an excellent substrate for the preparation of Ni-Mo 2 C/N-CW electrodes. Mo 2 C is well known for its considerable potential as a non-precious metal electrocatalyst with enhanced catalytic activity. The successful doping of nickel and nitrogen into molybdenum carbide not only promotes the formation of β-Mo 2 C, but also improves the electron transfer rate and mass diffusion pathway. Consequently, the Ni-Mo 2 C/N-CW electrode exhibits excellent performance in the hydrogen and oxygen evolution reactions (HER and OER, respectively). Only voltages of 89 and 253 mV are required to achieve a current density of 10 mA cm −2 , respectively. When the Ni-Mo 2 C/N-CW catalyst is used as both cathode and anode during hydrolysis, current densities of 10 and 100 mA cm −2 can be achieved with excellent durability and stability at voltages of 1.56 and 1.72 V, respectively. The distinctive porous structure of the wood substrate is of crucial importance for promoting the adsorption and dissociation of water molecules, enhancing the catalytic performance. In addition, the present material exhibits advantageous characteristics, including a high specific surface area and a significant number of adsorption sites, making it a very promising candidate for applications involving the adsorption of dyes, such as rhodamine B (RhB).
Zhenzhen Yang,Yuhan He,Pengfei Tang,Bangchong Zhu,Genlei Zhang,Jianbo He
Direct conversion of biomass-based fructose to 2,5-diformylfuran (DFF) has attracted much attention in recent years. In this study, molybdenum carbide anchored on glucose-derived carbon (β-Mo2C@C) was synthesized by a simple, green and economical method and was found to be highly active for production of DFF from 5-hydromethylfurfural (HMF) and fructose. DFF was obtained with high yields of 94.5% and 76.0% from aerobic oxidation of HMF and “one-pot” conversion of fructose under optimal reaction conditions, respectively. A probable mechanism involving Mo6+/Mo2+ redox cycles was proposed for β-Mo2C@C-catalyzed oxidation of HMF to DFF according to the experimental and characterization results. Furthermore, the β-Mo2C@C catalyst can be reused without much loss of catalytic activity, suggesting that β-Mo2C@C is highly stable.
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