Synthesis of cerium dioxide-based pigments with co-precipitated phosphate: tuning oxidation catalytic activity for cosmetic and paint applications

Cerium oxide, a popular ultraviolet screening agent in cosmetics, is hindered by its oxidation catalytic activity. Seeking an alternative to cerium phosphate, which increases particle size but lacks catalytic activity, we synthesized a novel cerium hydroxide-cerium oxide pigment by coprecipitating a small amount of phosphate. We chose a baseline Ce/P ratio of 10:1 based on preliminary tests showing that a moderate level of phosphate effectively reduces oxidation catalytic activity while still preserving key cerium oxide characteristics. We evaluated its composition, particle size, oxidation catalyst activity, and hue. Coprecipitation and subsequent heating yielded a yellowish pigment containing both cerium oxide and cerium phosphate. Compared to cerium oxide, our pigment exhibited superior smoothness. Additionally, samples prepared under low pH or high phosphate ratios demonstrated reduced oxidation catalytic activity. However, when applied as a pigment in oil paints, its hiding power was diminished. Our findings highlight a promising strategy for mitigating the catalytic drawbacks of cerium oxide while improving pigment properties, yet caution is warranted regarding its efficacy in paint applications. This study underscores the potential of cerium-based compounds in diverse fields, with room for optimization in specific applications. This study underscores the potential of systematically tuning cerium-based compounds for a range of applications, including cosmetics and paints, by exploring how pH and Ce/P ratio influence catalytic activity, coloration, and particle properties.