Synthesis Of Cobalt Complexes And Phosphides And Study On Photocatalytic CO₂ Reduction

Energy shortage,environment pollution and climate warming are major problems that perplex human beings,therefore,to solve twin problems of global warming and the energy crisis has attracted considering wide attention.Photocatalytic reduction of CO₂ to produce high value-added fuels as well as industrial chemicals like CO,CH₄,HCOOH,and other micromolecular organics offers a package solution to address both the increasing energy requirements and climate change.However,CO₂ is chemically inert,so converting it into fuels and chemicals requires considerable energy and suitable catalysts.This master's thesis paper studies mainly two visible light-driven systems involving molecular catalysts of Co?II?complexes and a heterogeneous hybrid catalyst of Co and Co₂ P nanoparticles embedded in carbon nanolayers codoped with N and P?Co-Co₂P@NPC?for CO₂-to-CO conversion.The achieved results are as follows:?1?Cyanide groups are introduced into the pyridine ring of tris?2-pyridylmethyl?amine?TPA?,and located on adjacent of the nitrogen atom.The ligand with cyano groups reacts with methanol catalyzed by CoCl₂·6H₂O to form new ligand with ether bonds=NH groups during synthesis procedure of Co?II?complex.The obtained complexes are characterized by X-ray diffraction analysis,mass spectrometry,infrared and so on.Study of properties of photocatalytic reduction of CO₂ for the as-prepared complexes with and without groups showed that catalytic activity of Co?II?complex with =NH groups is the best.The TON value is 30 and the CO selectivity is 66%.?2?The new mesoporous catalytic materials of Co and/or Co₂ P nanoparticles embedded on N,P-codoped graphitic carbon nanosheets was prepared loaded on N,P-doped carbon nanosheets are prepared by a one-pot method.Structures and morphology of the as-prepared materials were characterized by XRD,TEM,HRTEM,XPS,ICP and so on.The combination of the materials as a catalysts with a Ru?II?molecular photosensitizer presents highly photocatalytic activity for CO₂ photoreduction.The average generation rate of CO of the system was up to 35,000?mol h-1 g-1 with selectivity of 79.1% in 3 h for Co-Co₂P@NPC.After six cycle experiments,its activity retained the initial 96%.Moreover,the used catalyst was characterized by XRD,TEM,and XPS,which demonstrated that crystallinity,morphology,and microstructure of Co-Co₂P@NPC were well retained after the recycling experiments,indicating the hybrid Co-Co₂P@NPC catalyst had high chemical stability.