Iron Oxychalcogenides and Their Photocurrent Responses.

We report here the results of an experimental investigation of the electronic properties and photocurrent responses of the CaFeO Q and La 2 O 2 Fe 2 O Q 2 phases and a computational study of the electronic structure of polar CaFeOSe. We find that both CaFeO Q ( Q = S and Se) have band gaps and conduction band edge positions compatible with light-driven photocatalytic water splitting, although the oxysulfide suffers from degradation due to the oxidation of Fe 2+ sites. The higher O/ Q ratio in the Fe 2+ coordination environment in CaFeOSe increases its stability without increasing the band gap beyond the visible range. The photocurrent CaFeOSe shows fast electron-hole separation, consistent with calculated carrier effective masses. These results suggest that these iron oxychalcogenides warrant further study to optimize their stability and morphology for photocatalytic and other photoactive applications.