Significantly improved photo- and electro-chemical performance of CuS.PbS nanocomposites for dye degradation and paintable counter electrodes

[Display omitted] •Simplistic band-gap controlled development of CuS-PbS nanocomposite is realized.•SEM/EDS, XRD etc. proved the efficacy of pseudo-SILAR route for developing CuS.PbS.•∼100 % increase in the degradation of Congo-red dye is obtained.•In-depth EIS revealed improved charge carrier transfer dynamics in CuS.PbS.•CuS.PbS exhibited air-processablity and suitability for solar paint application. CuS nanoparticles (CuS NPs) are used in a variety of optical, photo-chemical, and photo-electrochemical applications. An unsophisticated but efficient strategy is reported here to enhance the performance of CuS by transforming it into CuS.PbS nanocomposites (NCs). A modified successive ionic layer adsorption and reaction method was employed to combine CuS NPs with PbS quantum-dots in a qualitatively-controlled way. Resultant CuS.PbS NCs were first qualitatively investigated using scanning electron microscopy coupled with an energy-dispersive spectroscope and an X-ray diffractometer. Owing to the improved optical behavior revealed by UV–vis spectroscopy, CuS.PbS NCs were employed first for photo-catalysis and then for electro-catalysis, where optimal CuS.PbS NCs (specifically, CuS.2PbS) ensued an ∼80 % degradation of the toxic Congo red dye. Moreover, the efficacy of the controlled deposition of PbS on CuS NPs was electrochemically investigated and a significant improvement in the imperative parameters, such as the charge transfer resistance at the electrode/electrolyte interface and electron lifetime, was obtained. CuS.2PbS NCs also exhibited air-processable and heat-treatable characteristics which demarcated its suitability for paintable counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSCs).