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

Photocatalytic CO2 reduction with naturally abundant H2O 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 ZnFe2O4/TiO2 heterojunction was fabricated, and its performance in CO2 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 CO2 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, CH4, and H2 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.