The perovskite devices were interfaced with the CoPcNH2@MWCNT catalyst to prepare the photocathode, which were subsequently encapsulated with epoxy to stop their degradation inside aqueous medium. For interfacing the devices with the catalyst, a conductive graphite epoxy (GE) paste was prepared by homogeneously mixing graphite powder with epoxy in 3:4 mass ratio. Araldite standard two-part epoxy was used for this purpose. The paste was then applied evenly over the Ag contact layer of the perovskite device, on top of which the graphite foil containing the CoPcNH2@MWCNT catalyst was attached. The device was then left to dry for 24 h to harden the GE layer, after which a Cu wire was attached for connection. Finally, the assembled device was encapsulated, and the edges were sealed using Araldite 5-min Rapid 2 component epoxy. The final PVK-based photocathodes are referred to as PVK|CoPcNH2@MWCNT.