18650 lithium battery 2600mah.The Institute of Science and Technology prepares low-cost fuel cell catalysts that exceed the current level of precious metal catalysis

　　Recently, the Center for Environmental and Energy Nanomaterials of the Institute of Solid State Physics, Hefei Institute of Physical Sciences, Chinese Academy of Sciences, has made new progress in selective hydrogenation catalytic conversion, constructing a Co-Nx active nanomaterial with ultra-high catalytic activity, selectivity and stability. site of non-noble metal catalysts. Relevant research results were published in the international journal "Advanced Materials" (Adv.Mater.2019, DOI: 10.1002/adma.201808341).

　　Biomass is one of the most abundant renewable resources on Earth and, with the help of the right catalysts, can be converted into fuels and chemicals that can replace fossil resources. Due to their rich oxygen content, selective hydrogenation of biomass-derived platform molecules is considered one of the most widely used methods in biomass fine chemical production. At present, the active components of hydrogenation catalysts mainly rely on the active sites of precious metals (Pt, Au, Pd, Ru, etc.), but their reserves are low and expensive, which seriously restricts their large-scale application. Therefore, the development of low-cost, non-precious metal highly active hydrogenation catalysts is the key to realizing biomass applications.

　　Traditional supported non-noble metal nanocatalysts have poor activity, selectivity and stability in the hydrogenation catalytic process due to poor morphology and size uniformity and single active sites. Recently, the preparation of low-cost, high catalytic activity metal-nitrogen-carbon structure catalyst systems based on metal-organic frameworks (MOFs) materials has attracted widespread attention from researchers. However, high-temperature direct carbonization of MOFs will lead to a decrease in N content and porosity, affecting the catalytic performance of the material. Therefore, it is necessary to construct appropriate nanostructures to maintain the catalytic activity of the material. ZIF-67 precursor-derived N-doped carbon nanotube-wrapped 3D transition metal nanocatalyst has been proven to be an efficient electrocatalyst due to its unique structure and composition design. Researchers attribute its excellent electrocatalytic performance mainly to the synergistic effect of chemical composition (appropriate N doping) and multi-level hollow structure. However, the catalytic potential of transition metal nanoparticles derived in situ based on this special structure of metal-nitrogen-carbon materials has not been fully exploited, especially there are few reports on traditional thermal catalysis.

　　To this end, the researchers used a two-step pyrolysis method to prepare ZIF-67-derived N-doped carbon nanotube-wrapped Co nanoparticle catalysts. Due to high-temperature stepwise pyrolysis, the growth of carbon nanotubes is more orderly, and the one-dimensional carbon nanotube structure can effectively prevent the growth and agglomeration of Co particles during the carbonization process, so that Co nanoparticles are highly uniformly wrapped in N-doped carbon At the top of the nanotube, the average particle size is 10.4nm, as shown in the figure. Analysis shows that the constructed catalyst has a large number of Co-Nx active sites, which results in the non-noble metal catalyst having ultra-high catalytic activity, selectivity and stability. Further analysis showed that this type of catalyst with high active sites can even selectively hydrogenate biomass-based compounds containing aldehyde, ketone, carboxyl and nitro functional groups at room temperature and convert them into corresponding high added value. Fine chemicals whose catalytic performance reaches or even exceeds the level of existing precious metal catalysts. Relevant research provides a new and effective way to prepare highly efficient non-noble metal-based hydrogenation catalytic materials, and provides an experimental basis for the understanding of new hydrogenation active sites.

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