  Photocatalytic nitrogen fixation from air directly under sunlight can
contribute significantly to carbon neutralization. It is an ideal pathway to
replace the industrial Haber Bosch process in future. A Fe-doped layered WO$_3$
photocatalyst containing oxygen vacancies was developed which can fix nitrogen
from air directly under sunlight at atmospheric pressure. The iron doping
enhances the transport efficiency of photogenerated electrons. The
photocatalytic efficiency is around 4 times higher than that of pure WO$_3$.
The optimum nitrogen fixation conditions were examined by orthogonal
experiments and its nitrogen fixation performance could reach up to 477 $\mu
\text{g} \cdot \text{g}_{\text{cat}}^{-1} \cdot \text{h}^{-1}$ under sunlight.
In addition, the process of nitrogen fixation was detected by situ infrared,
which confirmed the reliability of nitrogen fixation. Also, modelling on the
interactions between light and the photocatalyst was carried out to study the
distribution of surface charge and validate the light absorption of the
photocatalyst. This work provides a simple and cheap strategy for
photocatalytic nitrogen fixation from air under mild conditions.
