| Carbon based non-noble metal heterogeneous catalysts have drawn increasing interests in the field of catalysis and electrocatalysis because of their cheap precursors,diverse morphology,high surface area,excellent catalytic activity and good recyclability.Undoubtedly,they also have broad application prospects in the production of fine chemicals,Fischer-Tropsch synthesis,biomass conversion,fuel cells and so on.In this paper,a series of nitrogen-doped carbon supported non-noble metal catalysts were prepared through the strategy of adjusting multiple templates and precursors.The morphology,structure and components of the catalysts were analyzed by various characterization technologies.The catalytic performance of these catalysts was evaluated by selecting several representative model reactions.It was demonstrated that the as-prepared catalysts exhibit excellent catalytic activity and stability.The specific work includes the following three aspects:(1)Using silica sol as the hard template,the porous catalytic materials of cobalt-copper bimetallic supported on nitrogen-doped carbon were prepared.The anomalous redistribution of nanoparticles was revealed by TEM combined with other characterization methods(from nanoparticles' average diameter of 38 nm under annealing temperature of 800 o C to 27 nm under 700 o C),which helped to bring light on the synergistic effect between Co and Cu.ICP-MS determined the Cu and Co contents in Co0.7Cu0.3@NHPC-800 to be 2.96 wt% and 7.77 wt%.N2 sorption revealed the hierarchical porous carbon matrix with the surface area of 749 m2·g-1.The results of hydrogenation of aromatic nitroarenes demonstrated that this bimetallic catalyst exhibited excellent catalytic activity and good stability that it could catalyze nitrobenzene reduction under 80 o C,0.1 MPa H2 with the apparent activation energy of 26.2 k J/mol.In addition,the hydrolysis of ammonia borane under room temperature(25 o C),showing the best catalytic activity under the specific compositionratio of Co0.7Cu0.3 substrates.Finally,we proposed reasonable explanation for Co-Cu synergistic effect based on literature and characterization.(2)The bamboo-like nitrogen-doped carbon nanotubes embedded cobalt catalyst with microporous structure(denoted as Co@NCNTs-T)was fabricated through simple pyrolyzing our home-made cobalt dicyandiamide which was synthesized by precipitation conversion.The nanotubes have the mean diameter of 150 nm and mean length of 200 nm with rhe surface area of 166 m2?g-1.TEM and XPS revealed that Co NPs combined with isolated single-atom cobalt sites coexist in defect-rich NCNTs,which could bring about multiple catalysis activities.It performed unexpected high activity and selectivity in the hydrogenation of nitroaromatics under extremely mild conditions(40 o C,0.1 Mpa)with >99% conversion and selectivity.Furtermore,it displayed excellent electrocatalytic HER performance that achieved current density of10 m A?cm-2 at a small overpotential of 182 m V under acidic media(p H=0)and 231 m V under basic media(p H=14),which is comparable to other cobalt catalysts.Based on poisoning experiments we assumed that the active sites of in basic HER are Co nanoparticles while single-atom cobalt sites contribute to the acidic HER activities.(3)A simple and efficient soft-template assisted strategy for the large-scale preparation of non-noble metal single-atom catalysts was developed through grinding and one-step pyrolysis of dicyandiamide and cobalt phthalocyanine raw materials.The prepared single-atom cobalt catalysts exhibited high specific surface area(325m2·g-1)and thin-layered structure(with thin carbon layer of merely 4.81nm),showing superior catalytic performance in the transfer hydrogenation of nitroaromatic compounds to nitroamines under 120 o C in the presence of 4.2 equivalent of formic acid as the reductant. |
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