[Abstract]

Transition metal oxides (TMO) and dichalcogenides (TMD) have attracted great attentions due to their promising applications in electronics, photonics, energy and electrochemistry. Anionic Defects such as oxygen vacancy and sulfide vacancy in TMOs and TMDs play an essential role in altering the electronic, magnetic, optical and catalytic properties of the materials. The mechanisms by which these defects affect these properties of are still unsettled. In this work, perovskite-based oxides (ABO3) and MoS2 were used as the model systems. We reveal systematically how anionic defects affect the electronic structure and electro-catalytic activity. The defects were introduced into the model systems by several approaches include thermal annealing, electrochemical reduction and ion irradiation. Our results show that anionic defect engineering is an effect tool to enhance the electro-catalytic activity of TMO and TMD, and can be used to for other applications such as electronics, optoelectronics and electrochemistry.