Preparation Of Fe,Co And Ni Phosphides And Studies Of Ammonia Borane Hydrogenation And Photocatalytic Reduction Of CO₂ Using As-prepared Catalysts

Fossil fuels based on coal,oil and natural gas are the main sources of energy consumption in today’s society.Over exploitation of fossil fuels has caused a series of problems such as depletion of fossil fuels,greenhouse effect and environmental pollution.Therefore,the development of clean renewable energy sources,and reducing CO₂ emissions is particularly important.Hydrogen as a clean energy receives considering attention,and photocatalytic reduction of carbon dioxide offers a way to capture and use of carbon sources.To search for a cheap and highly efficient catalyst has become a research hotspot in today’s society.The studies of the master’s thesis were focused on the preparation of high active nano-catalysts of non-precious transition metal phosphides and the titanium oxide supported cobalt nanoparticle,as well as catalytic dehydrogenation of ammonia borane and photocatalytic reduction of carbon dioxide.1.The use of sodium hypophosphite as a source of phosphorus,Co₃O₄,NiO,Fe₃O₄ and other metal oxides as the metal source,The metal phosphides（CoP-Co₂P、CoP-Ni₂P、CoP-FeP,etc.）were prepared,their structures and morphology were characterized by XRD,SEM,ICP,TEM and so on.Whereafter,the as-prepared nanomaterials were used to catalyze dehydrogenation of ammonia borane,and the obtained showed that the order of the catalytic activity for hydrogen evolution is CoP-Co₂P>CoP-Ni₂P>CoP-FeP.A systematic study on amounts of CoP-Co₂P,reaction temperature,alkali concentration and cycle stability were conducted.When the sodium hydroxide concentration was fixed in 0.8 M at 25℃and 35℃,the TOF values of CoP-Co₂P were up to 34.5 and 55.7 mol_（H2）mol^-1_{（CoP-Co2P）}min^-1,respectively.Compared with the previous reports on the catalytic dehydrogenation of ammonia borane,CoP-Co₂P shows excellent catalytic activity.2.Co nanoparticles in hollow TiO₂ nanorods were embedded to form a hybrid catalystby one-step calcination of a self-assembly of cobalt（II）and tetrabutyl titanate.And carbon coated Co@TiO₂ nanorods（denoted as Co@TiO₂/C）were synthesized via calcination of dopamine polymer encapsulated Co@TiO₂ nanorods.Structures and morphology of the nanomaterials were characterized by XRD,SEM,BET,ICP and so on.After coating with a carbon nanolayer,the photocatalytic activity of the material towards CO₂-to-CO conversion was boosted,and the production rate of CO increased to 28,500μmol h^-1 g^-1 with a selectivity of 78.1%.After six cycles,the catalytic activity still kept initial 96.3%.It is thus shown that the Co@TiO₂/C has excellent catalytic activity for photocatalytic reduction of carbon dioxide,good selectivity for product CO,and excellent stability.