| Transition metal alloy and transition metal oxide nanocomposite catalysts are two kinds of important catalysts,which are widely used in the field of fine chemistry,petrochemical industry and environmental catalysis.However,the traditional preparation methods are inevitable to involve complex procedure,too many influence factors and poor repeatability,leading to a poor catalytic effect of the as-prepared catalyst.To solve the problem,we fabricated efficient NixFey NPs@C and CoO NPs@C nanocomposite catalysts with a simple one-step solid-state pyrolysis method from a single-source precursor.The detail contents are introduced as follows:NixFey alloy nanoparticles embedded in graphite carbon(NixFey,NPs@C)were synthesized by a thermal reduction method using single-source NixFey layered double hydroxide intercalated with salicylate anions as precursors without reducing agent and additional carbon source.By virtue of the tunable composition of cations on the layer properties of LDH precursor,we can easily synthesize a series of NixFey NPs with different Ni/Fe ratios embedded in graphite carbon by adjusting the raw material proportion.The as-prepared products were characterized by XRD,SEM,HRTEM,BET,Raman,FTIR and XPS,and the result are as fllows:in the as-prepared nanocomposite catalyst,the high-crystalized and pure NiFe alloy NPs(8-12 nm)are uniformly embedded in the graphite carbon with a ultra-high alloy NP loading amounts(～80%),and connect to graphite with a C-O-M(Metal)structure.The graphite carbon matrix exhibits a large surface area(141.36 m2/g)and mesoporous structure,which benefits the contact between the substrate and catalytic sites.As a result of the existence of a large number of hydroxyl groups on the surface of graphite carbon matrix,the as-prepared catalyst gains a favorable hydrophilic property,which is in favor of its dispersion in aqueous solutions.The obtained catalyst exhibited outstanding catalytic activities toward the catalytic reduction of p-nitrophenol(p-NP),and the optimized Ni5Fe1 NPs@C even showed a higher catalytic effect than the commercial Pt/C(20%)catalyst and the state-of-the-art Pd/C(10%)catalyst under the same conditions.In addition,the catalyst can be easily recycle for reuse because of its soft magnetic nature,and after running for 20 cycles in the reduction reactions,the conversion efficiencies of p-NP can be achieved above 95%,revealing a excellent stability.In addition,the as-prepared catalyst also exhibits good catalytic effect at low concentration of NaBH4(～20 eqv)and wide pH range(5-11)of p-NP solution in the catalytic reaction.CoO nanoparticles embedded in graphite carbon(CoO NPs@C)were synthesized by a thermal reduction method using single-source layered cobalt hydroxide intercalated with salicylate anions as precursors without reducing agent and additional carbon source.The as-prepared products were characterized by XRD,SEM,HRTEM,BET,Raman,FTIR and XPS,and the result are as fllows:in the as-prepared nanocomposite catalyst,the high-crystalized and pure CoO NPs(～6 nm)are uniformly embedded in the graphite carbon with a ultra-high CoO NP loading amounts(～64%),and connect to graphite with a C-O-Co structure.The graphite carbon matrix exhibits a large surface area(141.36 m2/g),mesoporous structure,and a large number of hydroxyl groups on the surface.In addition,the existence of oxygen vacancies in the CoO NPs is beneficial to the catalytic effect of as-prepared catalyst.Use the as-prepared catalysts in the catalytic reduction of p-NP,the results showed that different products derived by different calcination temperatures exhibited diverse catalytic effects,and the CoO NPs@C-450 derived by 450℃ exhibited the highest catalytic activity,which is better than that of commercial Pt/C(20%)catalyst.What is more,the catalyst can be easily recycle for reuse because of its soft magnetic nature,and after running for 5 cycles in the reduction reactions,the conversion efficiencies of p-NP can be achieved above 95%,revealing a excellent stability. |
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