Synthesis, Characterization And Catalytic Performance Of Co-based Water Oxidation Catalysts

To solve the problem of energy crisis and environmental pollution, the development of clean and renewable energy has become increasingly urgent. Scientists believe that splitting water by simulating photosynthesis is one of convenient methods. Due to sluggish kinetics, water oxidation is the bottleneck of overall water splitting. Therefore,scientists try to design various kinds of catalysts to accelerate the process. Due to its abundance and robust activity, Co-based oxides are regarded as one of the ideal water oxidation catalysts. The study of Co-based water oxidation catalysts is relatively less, and there are still some Co-based catalysts unreported. Most of cobalt oxides are lack of ferromagnetic character and the activity decreases in the recycling experiments. Based on this, the introduction of the strong ferromagnetic compounds will make catalysts become much easier for recycling. The research of active sites is ambiguous. Through doping with different atoms to influence the activity of catalysts, we can investigate the active sites and some internal effect. Besides, we study the performance of mononuclear Co-based complex. Based on the above points, this thesis is followed by four aspects:1 Co3V2O8 was synthesized and characterized, which holds the structure of hexagon umbrella. Under the reaction system, the apparent TOF value and the initial rates were 10.9 μmol s-1 m-2 and 31.7 μmol s-1 g-1, respectively.2 Considering catalyst’s loss in recycling experiments, we synthesized strong ferromagnetic NiO/CoO/Fe2O3 composite by simple hydrothermal co-precipitation method. Due to the three components combined together firmly, the composite produces surface charge effect which leads to enhanced catalystic activity. The composite has strong ferromagnetic properties so that the activity remained very well during the recycling experiments.3 Based on the design and research of the above catalysts, we try to dope different heteroatom(Ni, Cu, Zn) into the lattice of Co3O4. According to photochemical, chemical and electrochemical conditions, it follows an interesting activity order: NiCo2O4 > CuCo2O4 > ZnCo2O4. Based on the order, we studied internal synergy effect and the catalysts’ active sites.4 In addition to research of Co-based oxides, we synthesized a mononuclear Co-based complex and investigate the activity of water oxidation and stability. The optimal TON of this complex is 1610, which, to the best of our knowledge, is the largest TON among metal-organic complexes in photocatalytic water oxidation system. A series of characterization techniques confirm that the complex is a robust and stable water oxidation catalyst.