Mesoporous Ti-substituted NiO nanosheets as an efficient electrocatalyst for triiodide reduction in dye-sensitized solar cells

In this work, a novel two-dimensional hexagonal mesoporous nickel oxide (2D-HM NiO) and titanium substituted NiO (Ti (1, 3, 5, 7 and 9 mol%)-NiO) nanosheets (NSs) are synthesized via a one-step hydrothermal method. The as-prepared 2D-HM NiO and Ti (1–9%)-NiO NSs are used to fabricate cost-effective counter electrodes (CEs) for DSSCs. The DSSCs device made with NiO and 1% of Ti-substituted NiO (1-TNO) CEs show excellent electrochemical properties and photovoltaic performance. The 100 consecutive cycles of cyclic voltammetry (CV) shows that NiO and 1-TNO CEs have high chemical stability towards I ⁻ /I ₃ ⁻ redox mediator as compared with Pt CE. For the first time, the power conversion efficiency ( PCE) of DSSCs with NiO-based CE reached up to 4.08% whereas 1-TNO CE a PCE slightly increased up to 4.12% which is relatively closer to Pt-based CE (5.34%) under identical working conditions. The high performance of NiO and 1-TNO CEs can be attributed to the large number of electrocatalytic active sites and fast ion diffusion, which is due to the high specific surface area of the 2D nanosheet structure with mesoporous nature.