Facile synthesis of ZnCo2O4@NiMoO4 with porous coated structures on carbon paper as stable and efficient Pt-free counter electrode materials for advanced dye-sensitized solar cells

A porous coating structure transition metal oxide ZnCo 2 O 4 @NiMoO 4 composite was successfully synthesized on the surface of carbon paper (CP) by a simple two-step hydrothermal method as a Pt-free material for titanium mesh substrate counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). According to BET test results, the material has a high specific surface area, which can provide abundant active sites for the redox reaction of electrolytes to enhance the utilization rate of sunlight by DSSCs, and the composite materials show remarkable electrocatalytic performance in reducing iodine electrolytes and improving the photoelectric conversion efficiency (PCE) of DSSCs. Therefore, the DSSCs equipped with ZnCo 2 O 4 @NiMoO 4 /CP material CEs achieve a PCE of 9.30 % (with J sc of 20.51 mA·cm −2 , V oc of 0.763 V, and FF is 0.60), which is much higher than that of Pt CEs (7.36 %) under the same light conditions. This is due to the excellent catalytic ability and good electrical conductivity of the composite material. On the other hand, because the titanium mesh can increase the contact area between the electrode material and the substrate compared with the FTO substrate, and the titanium mesh has good electrical conductivity, it can enhance the diffusion ability of I - / I 3 - to accelerate electron transmission.