Facile Synthesis of Mo₂C Nanocrystals Embedded in Nanoporous Carbon Network for Efficient Hydrogen Evolution

Abstract

Exploring facile and easily-scalable methods for synthesizing earth-abundant, cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts is essential for the mass production of hydrogen as a clean and sustainable energy carrier. We report here a simple strategy to produce Mo 2 C nanocrystals embedded in carbon network (Mo 2 C@C) by the direct pyrolysis of ammonium molybdate and polyvinylpyrrolidone (PVP). It is found that PVP can be effectively used as a single source to form carbides and carbon network. The long polymer chain and coordinating capability with transition metal of PVP make it possible to form connected porous carbon network and well-dispersed Mo 2 C nanocrystals in several nanometers. The carbonization of PVP not only effectively in-situ prevents the aggregation of Mo 2 C nanocrystals during their formation, but also provides conductive porous matrix. As a result, the Mo 2 C@C composite exhibits the superior electrocatalytic performance for HER, which can be ascribed to the large number of active sites from plenty of small Mo 2 C nanocrystals and the efficient mass and electron transport network from carbon matrix. This strategy may inspire the exploration of cost-effective functional polymer as single source for both carbon precursor and nanostructure-directed reagent to mass-produce well-defined metal carbides nanostructures embedded in porous carbon network for energy applications.

Molybdenum Carbide-Reduced Graphene Oxide Composites as Electrocatalysts for Hydrogen Evolution

“…The XRD patterns in Figure b show the impact of adjusting the urea/MoCl 5 ratio on the crystallinity of Mo 2 C NPs synthesized using the microwave-based approach. The XRD pattern for R = 7 exhibits sharp diffraction peaks, which can all be indexed as hexagonal β-Mo 2 C (JCPDS pattern: 35-05-0787 − ). The peaks at 2θ = 34, 38, 39, 52, 62, 69, 74, and 76 correspond to the (100), (002), (101), (102), (110), (103), (112), and (201) planes of β-Mo 2 C. No other crystalline phases were observed in the R = 7 sample nor was any indication of graphitized carbon seen in the 2θ range of 21–26° .…”

The Role of Hydroxide Binding Energy in Alkaline Hydrogen Oxidation Reaction Kinetics on RuCr Nanosheet†

“…It is worth noting that alkaline HER performance of RuCr‐2 is higher than most of the reported PGM‐based HER catalysts (Table S4). Furthermore, the Tafel slopes of RuCr‐2, commercial Pt/C, Ru nanosheet and crystalline Ru are measured to be 75.38, 76.53, 86.1 and 96.12 mV·dec –1 , respectively (Figure S12b), [ 40‐41 ] indicating RuCr‐2 possessing a rapid charge transfer kinetics. The mass activity of RuCr‐2 HER performance shown in Figure S12c and Figure S12d is more than two times higher than that of commercial Pt/C.…”

Efficient Contact between H2O and N‐Coordinate Ru Nanoparticles in Three‐Dimensionally Ordered Macro/Mesoporous Carbon Boosting Alkaline HER†

“…[ 1‐2 ] Hydrogen, as a green, clean, and sustainable energy carrier, has been regarded as a potential fossil fuel alternative. [ 3‐4 ] At present, the alkaline electrocatalytic water splitting producing hydrogen utilizing renewable energy sources such as wind power and photovoltaic electricity has gained increasing attention of researchers due to its independence from fossil fuels, zero carbon emissions and low cost. [ 5‐8 ] In alkaline electrolytes, water electrolysis needs to overcome additional obstacles to break the O—H bond, resulting in a sluggish kinetics performance of hydrogen evolution reaction (HER).…”