Graphene-Based Single-Atom Catalyst Nanobots for Advanced Water Treatment

Self-propelled micro/nanobots, combining miniaturization and autonomous swimming capabilities, are emerging as powerful tools for enhancing pollutant removal in water, offering significant advantages over traditional static mechanisms. The dynamic nature of these bots promotes more efficient pollutant degradation and removal through faster mass transport and uniform mixing. On the other hand, single-atom catalysts (SACs) have demonstrated enormous potential in the remediation of organic pollutants. However, they are often restricted by diffusive mass transport, thus requiring agitation by external means to increase yield. In this study, we present a unique concept of integrating SACs in chemically driven nanomotors to design a multifunctional, magnetic, single-atom graphene acid–based nanobot (Fe3O4-GSH-GA-Cu; FGGC nanobots). Such a platform enables rapid and efficient pollutant degradation as well as offers reusability and easy recovery by exploiting the synergy between SAC, propulsion, and magnetic guidance, leading to higher efficiencies and shorter cleanup times compared to conventional catalysts. These nanobots were synthesized by chemically anchoring copper-loaded graphene acid to magnetic Fe3O4 nanoparticles. The single-atom copper catalyst promotes organic pollutant degradation via the Fenton reaction, acting as an engine that decomposes hydrogen peroxide fuel. The magnetite nanoparticles contribute to the degradation process, ensure self-propulsion, and enable external magnetic control. The FGGC nanobots were propelled by oxygen bubbles generated from Fe3O4-triggered catalytic decomposition of hydrogen peroxide, achieving a high speed of 0.510 mm s–1 in 2% H2O2 which increased to 2.061 mm s–1 in 15% H2O2. The as-prepared nanobots demonstrated excellent pollutant removal efficiency, degrading 97%, 96%, and 91% of orange G (OG), azithromycin (AZI), and 4-nitrophenol (4-NP), respectively, within just 30 min. Furthermore, the specific productivity of these single-atom nanobots exceeds that of previously reported nanobots. This reusable, single-atom nanobot-based degradation strategy offers a promising approach for advanced water treatment without the need for external energy input.