Bioinspired Haloperoxidase Mimicry by CeO2-based Nanozymes with High H2O2-to-HOBr Conversion Combats Marine Biofouling on Steel Surfaces

Biofouling is a critical issue for marine architectures immersed in seawater, like pipelines, ship hulls, and offshore platforms. It involves the accumulation of organisms on submerged surfaces, leading to environmental issues and economic losses. For instance, the bio-accumulation carried by boats may introduce invasive species and alter habitats to species of the region. It also increases the hydrodynamic drag for boats, leading to increased fuel consumption. This, together with the costly manual cleaning and periodic painting of antifouling paints, results in an annual expense over $180 million for the US Navy fleet. Currently, more than 95% of antifouling coatings rely on the release of Cu biocides from resin matrix to prevent bio-accumulation. However, restrictions on their use in some regions/ countries have arisen due to concerns on the metabolic effects of Cu accumulation in marine organisms. Bioinspiration from nature can guide the development of eco-friendly coatings. Marine algae, for example, utilize haloperoxidases (HPOs) to combat biofouling by converting H2O2and Br−in seawater into HOBr, which interferes bacterial communication and damages their membranes. Since natural enzymes have limitations in preparation and stability, CeO2nanozymes with intrinsic HPO-like activity and high biocompatibility have emerged as a promising artificial alternative in recent year. Yet, these nanozymes unavoidably catalyze H2O2decomposition, which restricts their HPO-like activity, particularly in seawater with low H2O2concentration. Our recent work discovered that octahedral CeO2nanozymes enclosed by (111) surfaces can entirely suppress this side reaction, enabling efficient H2O2-to-HOBr conversion. However, when dispersed in resin and applied as a coating on steel surfaces, their HPO-like activity is significantly reduced due to limited access to H2O2and Br−. The practical application of this material for catalytic marine antifouling is thus hindered. Very recently, we developed a one-pot synthesis of ultrasmall CeO2nanozymes embedded in resin-derived porous carbon frameworks (CeO2/CF) with strong HPO-like activity and adhesion to steel surfaces. To our surprise, the side reaction can be simply controlled by the calcination gas used during their preparation. This project aims to reveal the underlying mechanisms, which will guide the optimization of their HPO-like activity for later antifouling fieldworks in marine conditions. Additionally, we will couple their photoactivity in H2O2production and explore integration with piezo/thermal catalysts to enhance local H2O2concentration. The success of this project will hold great potential for the development of advanced coatings for marine architectures to combat biofouling in asustainableandgreenapproach.