Synthesis of metal oxides with improved performance using a solvothermal method

We have explored a solvothermal method for synthesizing various metal oxides in alcohol or glycol media at temperatures around 300°C. This review summarizes our recent results on the solvothermal synthesis of metal-oxide nanoparticles and their catalytic and photoluminescence performances. We have described the principles of solvothermal processing by classifying solvothermal methods according to the type of solvent used as follows: alcohol, vicinal glycol and 1,4-butanediol. (1) Solvothermal reaction of metallic cerium in alcohol yields a colloidal solution containing CeO2 nanoparticles, and the pore structure of the CeO2 coagulate can be controlled by the choice of bases added to the colloidal solution. Furthermore, the solvothermally synthesized CeO2 nanoparticles show good redox properties and an improved performance as a catalyst support in the selective oxidation of benzyl alcohol to benzaldehyde. (2) Solvothermal method in vicinal glycol produces an inorganic–organic composite, which is an effective precursor for the synthesis of metal-oxide nanoparticles. Nb2O5 nanoparticles synthesized via a solvothermal reaction in ethylene glycol show high activities as photocatalysts for the selective oxidation of alcohol. (3) Solvothermal reactions in 1,4-butanediol can yield various mixed oxides directly. Mn-modified hexagonal YbFeO3 synthesized by the solvothermal method has a higher catalytic activity for hydrocarbon combustion when compared to noble metal catalysts.