Thermo-chemical environment-dependent vacancy formation in FeWO: A DFT study.

FeWO, known for its potential in photocatalytic and electrocatalytic applications due to its chemical stability and band structure, can exhibit various defects that influence its performance. Density functional theory (DFT) calculations were employed to determine the formation energies of iron, tungsten, and oxygen vacancies under different thermo-chemical environments within the Fe-W-O ternary system. The study reveals that oxygen vacancies are more likely to form in reducing environments rich in FeO and FeO and it can offer practicality through facilitating the formation of reactive oxygen species (ROS), which contribute to photocatalytic performance. Meanwhile, the formation of iron vacancies is more readily achieved in oxygen-rich conditions, particularly when Fe-W-O compounds can be constructed. Similarly, tungsten vacancies form more often in oxygen-rich environments but less in iron oxide-rich conditions. In conclusion, this study provides a more comprehensive understanding of the nature of vacancy defects in FeWO and elucidates the environmental conditions that can be exploited to maximize or minimize vacancy formation for the control of catalytic activity.