Fe-carbon dots enhance the photocatalytic nitrogen fixation activity of TiO2@CN heterojunction

A multiheterojunction structured photocatalyst FeN-CDs/TiO2@CN was prepared by a facile low temperature anneal method, which exhibits excellent photocatalytic nitrogen fixation activity. The CDs with abundant electrons and functional groups transferred electrons to active centers more effectively, and the tightly heterogeneous interface between the carbon dots/TiO2 and graphic carbon nitride improves the separation of electro-holes. In addition the coexistence of two types of TiO2 (anatase and rutile) is more advantageous for NRR compared with pure rutile or anatase TiO2. It was confirmed that FeN-CDs is the active site for nitrogen fixation reaction. The photocatalytic nitrogen fixation performance of FeN-CDs/TiO2@CN reached 9.365 mg h−1 gcat-1. Temperature-programmed desorption (N2-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed to prove the efficient adsorption and protonation of N2 over FeN-CDs. A feasible mechanism was proposed for photo-induced charge separation and nitrogen photofixation on FeN-CDs/TiO2@CN.