A new strategy for utilization of NIR from solar energy—Promotion effect generated from photothermal effect of Fe3O4@SiO2 for photocatalytic oxidation of NO

Photothermal effect was for the first time utilized to capture the energy from infrared light and to promote the photocatalytic oxidation activity of NO by a simply mechanical mixing of traditional photocatalysts and core-shell structured Fe3O4@SiO2. Fe3O4@SiO2 absorbed the infrared light, transferred it into thermal energy based on photothermal effect, which then accelerated the NO photocatalytic activity of traditional photocatalysts. This promotion effect led by the addition of Fe3O4@SiO2 was confirmed by several classical photocatalysts such as TiO2, g-C3N4, BiOI and CeO2. To quantitatively characterize the photothermal effect, thermo images were taken with a thermo imager to obtain the average temperature rise of samples under the illumination of simulated solar light. Specially, P25/Fe3O4@SiO2 was studied in depth for illustration of the promotion mechanism. Experimental results showed that with the contribution of SiO2 shell, the photocorrosion of Fe3O4 didn’t occur during photocatalytic oxidation process and the photothermal effect of Fe3O4 was maintained. The quantity of Fe3O4@SiO2 was a vital factor for promotion of photocatalytic activity and the optimum mass ratio of P25 and Fe3O4@SiO2 was 3–1. After 120 min of illumination, the temperature of optimum P25/Fe3O4@SiO2 rose to 57.4 °C from 25 °C and its NO conversion capability showed an enhancement of 38.9% with the comparison to pure P25. The experimental results confirmed that the rise of temperature was attributed to the photothermal effect and its contribution was the same as the directly heating of photocatalysts. Furthermore, the enhancement of NO conversion capability around 30–40% was observed for the Fe3O4@SiO2 mixed anatase TiO2, g-C3N4, ZnO, BiOI and CeO2. In sum, we developed a new strategy for utilization of NIR light of solar energy to facilitate the photocatalytic reactions.