In order to fabricate mechanically stable PCN-based photocathodes, we used porous NiOx films on FTO as a scaffold for subsequent deposition of PCN using chemical vapor deposition from urea decomposition products . Nickel oxide is well established as a large bandgap (~3.3 eV) p-type semiconductor that can be used as a hole collector and/or hole transport layer in dyesensitized photoelectrochemical cells ]. Since the intrinsic conductivity of PCN is typically very low , we envisaged that NiOx should effectively extract holes from PCN and transport them into the FTO substrate, enhancing thus the charge separation in our photocathodes. The top-view SEM images show that the NiOx layer consists of polydispersed particles of an average diameter of ca. 120 nm (Figs. and). The NiOx particles aggregate to form a porous network (Fig. ), and build a fiber-like structure after modification with TiO2 and/or PCN (Fig. ). The presence of TiO2 is known to be beneficial for the deposition of PCN since the surface OH groups at titania surface act as a catalyst for the conversion of urea decomposition products to PCN . The shape of the nickel oxide particles was not affected by the deposition of TiO2 (Fig. and; see also SEM analyses of NiOx-TiO2 at higher magnification in Supporting Information, Fig. ), indicating that the TiO2 layer is presumably very thin (< few nm). The slight increase of the particle average size to around 135 nm after the deposition of PCN is attributed to the PCN coating of the NiOx particles. The electronic absorption spectra of all four photocathodes are shown in Fig. . For photocathodes without PCN, the fundamental absorption edge is below 350 nm (black and green curve), while the deposition of PCN clearly leads to increased absorption in the visible range (blue and red curves), which is evidenced by the yellowish color of these electrodes (Fig. ). This effect is similar to what is known for anatase TiO2 (bandgap of 3.2 eV), where the deposition of PCN (bandgap of 2.7-2.9 eV) shifts the absorption edge to the visible. In order to determine the bandgap energies using the Tauc formalism, diffuse reflectance spectra of powders scratched off the electrodes were recorded (see Supporting information, Fig. ).