Enhanced tribocatalysis through combining charge transfer with electron jumping in co-doped NiO magnetic nanocatalyst for water purification

Mechanical friction energy is a ubiquitous green energy that can be collected and transformed into electrical energy for water treatment, a concept theoretically referred to as tribocatalysis. The efficient removal of organic pollutants from wastewater by tribocatalysis still faces challenges. Employing doping technology to introduce metallic elements into materials is anticipated to enhance tribocatalytic performance by improving material properties. In this work, NiO and x wt% Co-doped NiO (x = 3, 5, 7, and 9) nanocatalysts are prepared using a coprecipitation method. The incorporation of Co effectively reduces the bandgap of NiO, enhancing tribocatalytic decomposition performance through the synergistic effects of charge transfer and electron transition. Notably, the optimized 7 wt% Co–NiO nanoparticles demonstrate the leading performance in the decomposition of rhodamine B (RhB), with a decomposition ratio of 96.7% after 120 min, representing a 23.1% increase over pure NiO. Electrochemical impedance spectroscopy (EIS) demonstrates that Co doping reduces the charge transfer resistance of NiO, resulting in the production of more reactive species. Radical trapping experiments and electron paramagnetic resonance spectroscopy (ESR) reveal that both superoxide radicals (·O₂⁻) and holes (h⁺) are key active radicals in dye decomposition. Furthermore, the 7 wt% Co–NiO nanocatalyst exhibits excellent stability and magnetic recyclability, retaining an 87.1% decomposition ratio after five cycles. The Co–NiO nanocatalyst, with these advantages of excellent tribocatalysis performance, low cost, and magnetic recyclability, has potential for application in wastewater treatment through harvesting and utilizing environmental mechanical friction energy in the future.