PbS nanocrystals decorated Reduced Graphene Oxide for NIR responsive capacitive cathodes

Novel hybrid nanocomposites formed of 1-Pyrene Carboxylic Acid (PCA) functionalized Reduced Graphene Oxide (RGO) sheets, surface decorated with UV–Vis–NIR light-harvester PbS nanocrystals (NCs), are prepared by means of an in situ colloidal chemistry approach, using oleic acid (OLEA) as a surfactant. PCA molecules anchored onto the RGO sheets feature carboxyl groups that serve as coordinating sites for the PbS NCs heteronucleation. Here, the mechanism underlying the NCs decoration of RGO is investigated and the interplay between the concentration of PCA and OLEA and the Pb precursor:OLEA molar ratio are demonstrated able to careful control NCs morphology and size distribution, governing also RGO covering density. Remarkably, PCA-RGO/PbS NCs modified Indium Thin Oxide (ITO) electrodes show an electrochemical specific capacitance much higher than that characterizing the single components of the nanocomposite, that can be further enhanced under illumination in the NIR. The nanocomposite modified electrodes demonstrate to behave as (photo)electrochemical supercapacitors, chemically stable, able to work both as (photo)charging and blocking electrodes, exhibiting a photocathodic behavior. The investigation of the NIR-light enhanced photocapacitive characteristics of the hybrid (photo)cathodes provides useful insights on their future integration in devices, including electrochemical photocapacitors and photoelectrochemical (bio)sensors.