Controlled synthesis of Ce(OH)CO3 flowers by a hydrothermal method and their thermal conversion to CeO2 flowers

► Ce(OH)CO3 flowers were prepared in a water-N2H4 complex. ► Influences of the N2H4 content and temperature on flower formation were discussed. ► CeO2 flowers were prepared by thermal conversion of Ce(OH)CO3 flowers at 500 °C. ► The Eg of CeO2 flowers is 2.66 eV, and lower than that of bulk ceria.