Study Of Ionic Water Oxidation System

Make full use of renewable energies as the substitute to the traditional energy is crucial. Among them transforming solar energy into chemical energy, such as splitting water into hydrogen and oxygen, is regards as the most beneficial and economical way. Over the past few years, a series of highly efficient Ru-bda (H2bda=2,2’-bipyridine-6,6’-dicarboxylic acid) type catalysts for water oxidation have been developed in our group. Mechanistic studies have revealed that the catalytic processes of water oxidation with Ru-bda catalysts were following a bimolecular coupling pathway. Therefore, increasing the opportunities of intermolecular interactions of this type catalyst is a suitable way to enhance their catalytic water oxidation activities.In this thesis, four Ru-bda type water oxidation catalysts Rul-4were synthesized and fully characterized by1H NMR and ESI-MS. In our design, these catalysts could congregate through ionic aggregation to increase the opportunities of intermolecular interactions in homogeneous solution. The common structures can be summarised as Ru(bda)L2(for Rul, L1=4,4’-carboxyl pyridine; for Ru2, L2=4-dimethylaminopyridine; for Ru3, L3=N,N-dimethyl-2-(pyridine-4-yl)ethanamine; for Ru4, L4=4-methyl-2-(2-(pyridine-4-yl)ethyl)phenol). These catalysts can form ionic species in water with different pH values.The activities of Rul-4in the chemical water oxidation reaction were investigated using [Ce(NH4)2(NO3)6] as an oxidation. Catalyst Rul adding NaOH forms catalyst Rul’and the catalyst Ru2adding HC1forms catalyst Ru2’. They can realize the water splitting and release oxygen. The TON of Rul’(1171.1) increases307compared to Rul (863.7) and Ru2’(584.7) increases126compared to Ru2(459.1). When the two catalysts in a state of ions are mixed by molar ratio1:1, the catalytic activity can be increased most. The TON of complex Rul+2(2117.8) increase2times compared to Rul (TON=1301.9) and Ru2(TON=948.9) separately at pH=4.0. While in pH=6.8the TON of catalyst Rul+2has little increase and in pH=1.0the TON has no increase.