N,F-Monodoping and N/F-codoping effects on the electronic structures and optical performances of Zn2GeO4.

First-principles density-functional calculation has been performed to investigate the synergistic effects of N and F doping on the photocatalytic properties of Zn2GeO4. Our results indicate that the presence of F facilitates the introduction of N by reducing the formation energy significantly. As N and F is codoped into Zn2GeO4, the mobility of the charge carriers is more rapid due to the dispersive levels above the valence band. And with the narrowed band gap the optical absorption spectrum red-shifts into the ideal visible-light region. Thus, we propose that the codoping of N and F can be a promising strategy to promote the photocatalytic performances of Zn2GeO4 under visible light.