High Potential Porphyrin Sensitized Nanocrystalline Metal Oxide To Assemble The Photo-anode For Water Oxidation

Visible light-driven water splitting into H2 is a potential solution to solve the current energy crisis,while water oxidation reaction has been the bottleneck of the process.Therefore,how to develop molecular water-oxidation device with hight efficiency has been the challenge in the field.The photoanodes are mainly composed of photosensizer,catalysts and semiconductor materials.So far,ruthenium polypyridine complesxes have been employed dominantly as PS,but the visible light collection is limited.By constrast,metallporphyrins with conjugate structure,similar to the chlorophyll in PSII,possessing strong S-band and Q-band absorption,which can improve the utilization of visible light.The oxidation potential can be tuned by the functional groups such as carboxyl group that can directly attach to the surface of semiconductor nanoparticles.Thus,it is of great significance to design high oxidized porphyrin photosensitizer for water oxidation molecular devices.In this thesis,we have designed zinc porphyrin(PS1),Ru-based catalyst(RuWOC1)and 4-pyridyl-hydroxamic acid ligand(L),and these structures are characterized by 1H-NMR.PS1 and RuWOC1 are attached to TiO2 photoanode surface by “PS1-L-TiO2” chain,which was tested by UV-Vis.The photoanode exhibited photocurrent of 45 μA/cm2 with a bias of 0.1 V(vs.Ag/AgCl)by photoelectric tests,and we proposed the mechanism of reaction.Furthermore,we synthesize high oxidative tin porphyrin as photosensitizer(PS2),water oxidation catalyst(RuWOC2)with silance-containing ligand and electron transfer mediator(M),and these structures are characterized by 1H-NMR.They are introduced to SnO2 photoanode by “Zr4+”,which was tested by UV-Vis.The initial photocurrent of800 μA/cm2 decreased to be 156 μA/cm2 with a bias of 0.4 V(vs.Ag/AgCl)by photoelectric tests.The oxygen generation after photo-assisted electrolysis for 100 s was confirmed by Clark-type oxygen,which was 1.24 nmol/L in 100 s and the Faraday efficiency was raised to 61%.The re-generation of photosensizer promoted by M and the supression of charge recombination were confirmed by surface photovoltage(SPV)spectroscopy and electrochemical impedance spectroscopy.