Fabrication of a novel rGO encapsulated nickel cobalt chalcogenide electrocatalyst as an efficient counter electrode to boost efficiency of dye-sensitized solar cells

Many materials have been explored as a counter electrode material to replace highly expensive platinum electrode in dye-sensitized solar cells (DSSCs). In this work, Cobalt–Nickel chalcogenide (Ni₂CoS₄/rGO) hybrid composite have been synthesised by facile ultra-sonication method. The various instrumentation techniques such as powder X-ray Diffraction (XRD), Scanning Electron Microscopy, Transmission Electron Microscopy, Raman, Ultra-Violet (UV), Photoluminescence (PL) are used to characterize the composite and illustrate the encapsulation of rGO. XRD studies disclosed the cubic phase crystalline system of all samples and crystallite size was noticed between 24.2 and 39.1 nm. The Ni₂CoS₄ is strongly encapsulated in the rGO sheets, which increases the surface area. The composition of Ni, Co, C, S and O was evaluated by Energy Dispersive X-ray analysis. UV-DRS analysis reveals that the optical band gap was decreased from 2.75 to 2.32 eV. Moreover, rGO incorporation improves the charge transfer separation, which was confirmed by PL studies. The textural properties of the Ni₂CoS₄/rGO are dramatically improved due to their high surface area (88.7 m²/g) and porous nature (46.5 nm), which is higher than bare Ni₂CoS₄ (44.6 m²/g and 33.3 nm). DSSCs have been fabricated with as-synthesized materials as counter electrodes. The outcomes showed that incorporation of rGO enhances the electron transport and reduced photo generated charge recombination in Ni₂CoS₄. Photovoltaic performance results revealed that owing to the huge surface area and porous nature of the Ni₂CoS₄/rGO composite, it exhibit outstanding power conversion efficiency of 8.62%, this is significantly better than bare Ni₂CoS₄ (3.56%). The rGO encapsulated Ni₂CoS₄ hybrid material as counter electrode thus offers a promising low-cost Pt-free counter electrode for DSSC applications.