Synthesis, Characterization And Properties Of Cobalt Phosphide Mirco-/nano-materials

Cobalt phosphides are currently of great scientific interest inmaterials science due to their novel magnetism, catalytic, photocatalyticproperties and anode-material properties lithium ion battery. Generally,cobalt phosphides include Co2P, CoP, CoP2, CoP3, and many cobaltphosphide mirco-/nano-material have broad potential applications. Cobaltphosphides exist in a variety of phases, so it is difficult to preparenanostructural transitional metal phosphides with definite stoichiometries.Nevertheless, it is still a huge challenge to material scientists developinga facile and feasible method to prepare morphology-and phase-controlledcobalt phosphides nanocrystals. In this dissertation, some cobaltphosphide micro-/nano-materials were successfully synthesized by thehydrothermal and solvothermal route. Through adjusting the experimentalparameters, the morphology of the final products could be successfullycontrolled. Simultaneously, the most research efforts have been focusedon the catalytic property of the as-prepared cobalt phosphides.Experiments showed that the as-obtained products presented outstandingcatalytic activity for the reduction of some aromatic nitro compounds inNaBH4aqueous solution. The main contents of this dissertation aresummarized briefly as follows:1. Cobalt phosphide (Co2P) nanostructures constructed by abundantnanorods were successfully synthesized at a large scale via an improvedwater–ethanol mixed-solvothermal route at170C for800min in thepresence of sodium dodecyl benzene sulfonate. White phosphorus andcobalt dichloride were used as starting reactants, hexamethylenetetramineas the pH adjustor. It was found that the morphology and crystallinity ofCo2P nanostructures could be tuned by the amount ofhexamethylenetetramine. Experiments showed that the as-prepared Co2Pnanostructures owned highly catalytic activity in the reduction ofaromatic nitro compounds by NaBH4. Furthermore, the as-obtained Co2P nanostructures also exhibited good adsorption capacities for Pb2+andCu2+ions in water resources, indicating that the as-prepared product hadpotential applications in environmental treatments.2.2D wall-like Co2P microstructures assembled by nanoflowers havebeen successfully synthesized via a simple solvothermal route at170Cfor16h, employing glycol as the solvent, CoCl2·6H2O, white phosphorus(WP) and NaH2PO2·H2O as starting reactants in the absence of anysurfactant or template. NaH2PO2was found to play important roles in theformation of2D wall-like Co2P microstructures. When the amount ofNaH2PO2below3mmol was used, flowerlike Co2P microstructures wereobtained. After further increasing the amount of NaH2PO2,2D wall-likeCo2P microstructures assembled by abundant nanoflowers were finallyformed. The as-obtained2D wall-like Co2P microstructures presentedoutstanding catalytic activity for the reduction of some aromatic nitrocompounds in NaBH4aqueous solution. Furthermore, experimentsshowed that2D wall-like Co2P microstructures exhibited strongercatalytic activity than flowerlike microstructures. This result clearlyuncovers the correlation between property and morphology of a material.3. Ternary CoNiP nanostructures have been successfully prepared via asimple solvothermal route without the assistance of any surfactant orstructure-directing reagent. Experiments showed that the as-preparedCoNiP nanostructures were consisted of microspheres wrapped byplentiful nanowires with the average diameter of~30nm and the lengthof~1μm on their surfaces. It was found that the as-prepared CoNiPnanostructures exhibited higher catalytic activity in reduction ofnitro-aromatic compounds than the binary Ni2P nanostructures preparedunder the same conditions.