**2. General principles of perovskite photocatalysis process**

In photocatalytic process, perovskite uses photon as a source of energy to initiate chemical reaction. As the photocatalyst is irradiated by light with energy equal or larger than the perovskite band gap, the electrons are excited from the valance band (VB) to the conduction band (CB), as a result photoreactive species such as e<sup>−</sup> and h<sup>+</sup> are created, which can be transferred to the surface of perovskite [17]. The factors affecting the photocatalytic activity of perovskite as a catalyst are namely, the excitement of the electron, separation of the electron and hole and photo-oxidation reduction reaction taking place at the surface of the catalyst [18].
