PbS nanocubes have been produced by a very simple solvothermal procedure that employs a unique molecule, ethylenediamine, as solvent and capping ligand to control the size and shape of nanocrystals. Detailed structural, optical and photoelectrochemical evaluation confirmed the suitability of these nanoparticles for photocapacitive applications, when synergistically combined with spin-coated BiVO4 photoelectrodes, as derived from the estimated energy diagram. Furthermore, the p-n junction facilitates the photo-oxidation of PbS nanoparticles under light irradiation. In the dark, the photogenerated charges are released providing an electric output response with a solar-to-current efficiency of 0.042 %, storing energy extra to the H2 produced by water splitting when the BiVO4 photoanode works under illumination. This study highlights the importance of the synthetic route and methodology to ensemble materials for advanced solar energy storage applications.