Photo-induced water splitting of water into H2 and O2 has been a major focus in the development of clean and renewable energy. The development of viable and efficient catalysts that facilitates O2 production remains the major challenge in the study of the corresponding half-reaction of water oxidation. There are plenty of metal oxides reported active in the catalysis of water oxidation. However, several important performance bench marks of those materials, such as the non-stoichiometric production of O2, slow reaction rate and/or low quantum efficiency, remain to be improved.
Ruthenium oxide (RuO2) has long been known as one of the most active catalysts for water oxidation. In this thesis are reported the syntheses of a series of mesoporous silica supported nanosized RuO2, their characterization, application in Ce(IV)-induced water oxidation and photo-induced water oxidation, and the kinetic study of the corresponding catalytic water oxidation reaction.
In Chapter 1, RuO2 nanoparticulates were pre-synthesized and wet-impregnated into mesoporous silica SBA-15. This material has been proven as the most efficient RuO2-based catalyst for Ce(IV)-induced water oxidation in terms of turnover frequency. In Chapter 2, the synthetic method of supported RuO2 was further optimized to achieve better dispersion and less aggregation of RuO2. As-prepared catalyst was proven the most efficient for photo-induced water oxidation compared to other RuO2 catalysts. It also led to one of the highest O2 yields and quantum efficiencies. In Chapter 3, Ce(IV)-induced water oxidation catalyzed by this material was kinetically studied, based on an independent electrode pair model. This study proved the applicability of this model in the analysis of the kinetics of the reaction catalyzed by supported RuO2 nanoparticulates, successfully simulated the kinetics of catalytic water oxidation, and clarified the electrochemical mechanism of this reaction. In Chapter 4, through the method of evaporation-induced self-assembly (EISA), nano-needle shaped RuO2 with low level of aggregation was well dispersed in and supported on mesoporous silica. It also exhibited excellent catalytic activity and reusability towards CeIV-induced water oxidation.