Boosting the Efficiency of Photoactive Rod-Shaped Nanomotors via Magnetic Field-Induced Charge Separation

Abstract

Photocatalytic nanomotors have attracted a lot of attention becauseof their unique capacity to simultaneously convert light and chemical energy intomechanical motion with a fast photoresponse. Recent discoveries demonstrate thatthe integration of optical and magnetic components within a single nanomotorplatform offers novel advantages for precise motion control and enhancedphotocatalytic performance. Despite these advancements, the impact of magneticfields on energy transfer dynamics in photocatalytic nanomotors remainsunexplored. Here, we introduce dual-responsive rod-like nanomotors, made of aTiO2/NiFe heterojunction, able to (i) self-propel upon irradiation, (ii) align withthe direction of an external magnetic field, and (iii) exhibit enhanced photocatalyticperformance. Consequently, when combining light irradiation with a homogeneousmagnetic field, these nanomotors exhibit increased velocities attributed to theirimproved photoactivity. As a proof-of-concept, we investigated the ability of thesenanomotors to generate phenol, a valuable chemical feedstock, from benzene undercombined optical and magnetic fields. Remarkably, the application of an external magnetic field led to a 100% increase in thephotocatalytic phenol generation in comparison with light activation alone. By using various state-of-the-art techniques such asphotoelectrochemistry, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance, wecharacterized the charge transfer between the semiconductor and the alloy component, revealing that the magnetic field significantlyimproved charge pair separation and enhanced hydroxyl radical generation. Consequently, our work provides valuable insights intothe role of magnetic fields in the mechanisms of light-driven photocatalytic nanomotors for designing more effective light-drivennanodevices for selective oxidations