Tandem Catalytic Antioxidant Nanoparticles Comprising Cerium Carbonate and Photoactive Metal Oxides

Journal Article · Wed Oct 20 00:00:00 UTC 2021 · ACS Applied Nano Materials

DOI: https://doi.org/10.1021/acsanm.1c02128 · OSTI ID:2228635

Mishra, Manish K.  ^[1]; Callejas, Juan F. ^[2]; Pacholski, Michaeleen L. ^[2]; Ciston, Jim ^[3]; Okrut, Alexander  ^[1]; Kumar, Ram ^[1]; Dyk, Antony Van ^[2]; Barton, David G. ^[2]; Bohling, James C. ^[2]; Katz, Alexander  ^[1]

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1. University of California, Berkeley, CA (United States)
2. The Dow Chemical Company, Midland, MI (United States)
3. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Molecular Foundry

While photoactive metal oxides such as TiO₂ find widespread use in paints and coatings as well as cosmetics and suncare products, they also generate reactive oxygen species (ROS), which degrade materials and are associated with human-health pathologies. Here, we demonstrate a robust and potent catalytic antioxidant consisting of earth-abundant cerium carbonate nanoparticles and micron-size Ce₂(CO₃)₃^.8H₂O, which are characterized by powder X-ray diffraction and scanning nanobeam electron diffraction. When dispersed with photoactive metal oxides, these cerium carbonate catalysts decrease the photodecomposition rate of organic dyes and commercial pigment colorants in aqueous media by up to 820-fold, as well as in acrylic coatings. X-ray photoelectron spectroscopy and kinetic experiments support the same tandem catalysis mechanism of photoprotection when using both micron-size Ce₂(CO₃)₃^.8H₂O and cerium carbonate nanoparticles. This mechanism involves ROS disproportionation (catalyzed by cerium carbonate) and H₂O₂ decomposition (partially catalyzed by TiO₂) pathways, both of which cerium carbonate also catalyzes on its own, crudely mimicking the function of the cascade system of superoxide dismutase and catalase enzymes. When cerium carbonate nanoparticles were dispersed at 2 wt % in polymethylmethacrylate, the transparency of the polymer film was preserved and the photo-oxidative degradation of the polymer was prevented following UV irradiation at 254 nm, which otherwise resulted in the loss of optical properties and hydroxylation as characterized by ATR-FTIR spectroscopy, in the control polymer lacking cerium carbonate. Similar observations were made regarding color preservation in paint films comprising dye and insoluble commercial colorant pigments. The material chemistry associated with this photoprotection catalysis is subtle and emphasizes the importance of both Ce(III) and carbonate together, as both CePO₄ and Na₂CO₃ are inactive. In conclusion, this emphasis is also apparent in comparisons of photoprotection catalysis with previously reported cerium oxide nanoparticles, which are significantly less active compared with Ce₂(CO₃)₃^.8H₂O under the same conditions.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC02-05CH11231; FG02-05ER15696
• OSTI ID: 2228635
• Journal Information: ACS Applied Nano Materials, Journal Name: ACS Applied Nano Materials Journal Issue: 11 Vol. 4; ISSN 2574-0970
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ROS
cerium carbonate
color retention
photoprotection
reactive oxygen species
tandem catalysis
weathering