Enhanced Photocatalytic CO₂ Reduction Performance via Photothermal–Magnetic Synergistic Effects for Solar Fuel Production

Abstract

Photocatalytic CO 2 reduction with naturally abundant H 2 O as the proton source has attracted widespread concern for its environmental and sustainable advantages. Nevertheless, the high recombination rate of photogenerated electron−hole pairs leads to unsatisfactory solar-to-chemical energy conversion efficiency. In this work, we proposed and validated a strategy that photothermal−magnetic synergistically promotes the separation of photogenerated carriers, as well as their transport, leading to boosted photocatalytic performance. A paramagnetic Z-scheme ZnFe 2 O 4 /TiO 2 heterojunction was fabricated, and its performance in CO 2 reduction was examined under concentrated full-spectrum light illumination with an applied external magnetic field. The built-in electric field of the Z-scheme heterojunction improved the dynamic properties of electron−hole pairs. At the same time, the thermal effect induced by infrared light played a crucial role in promoting CO 2 conversion. Importantly, the applied external magnetic field further suppressed the recombination of charge carriers via Lorentz force, magnetoresistance, and spin-polarization effects. As a result, the assistance of a magnetic field significantly increased the yields of CO, CH 4 , and H 2 in comparison to the absence of a magnetic field, with maximum enhancements of 25.3, 29.6, and 62.9%, respectively. Moreover, the excessive heating due to the higher concentrated ratio may induce magnetic disorder within the material, potentially reducing the magnetic field's ability to facilitate carrier transport. The photothermal−magnetic synergy mechanism was systematically explored. Our work has presented a new approach in which photothermal−magnetic effects synergistically contribute to solar fuel production.