Iron Oxychalcogenides and Their Photocurrent Responses.

We report here the results of an experimental investigation of the electronic properties and photocurrent responses of the CaFeOQ and La2O2Fe2OQ2 phases and a computational study of the electronic structure of polar CaFeOSe. We find that both CaFeOQ (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 Fe2+ sites. The higher O/Q ratio in the Fe2+ 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.

Photocatalytic and Photocurrent Responses to Visible Light of the Lone-Pair-Based Oxysulfide Sr6Cd2Sb6S10O7.

We present a combined experimental and computational study on the recently reported oxysulfide Sr6Cd2Sb6S10O7. Our spectroscopy and photoelectrochemical measurements and tests for photocatalytic activity indicate the potential of Sr6Cd2Sb6S10O7 for photocatalytic applications. In particular, the transient photocurrent response shows a reproducible photogenerated current which depends on light intensity and which indicates an efficient electron-hole separation upon visible light illumination. Density functional theory calculations, combined with crystal orbital Hamiltonian population analysis, give insights into the electronic structure of Sr6Cd2Sb6S10O7 and the origin of its physical properties. Our comprehensive investigation into Sr6Cd2Sb6S10O7 reveals the roles of its polar structure, polar Sb3+ coordination environments, and the 5s2 lone pair in making this compound a potential candidate for solar water splitting photocatalysis.