Conversion of Sewage Water into H(2) Gas Fuel Using Hexagonal Nanosheets of the Polyaniline-Assisted Deposition of PbI(2) as a Nanocomposite Photocathode with the Theoretical Qualitative Ab-Initio Calculation of the H(2)O Splitting

This study is very promising for providing a renewable enrgy (H(2) gas fuel) under the elctrochemical splitting of the wastwater (sewage water). This study has double benefits: hydrogen generation and contaminations removel. This study is carried out on sewage water, third stage treated, from Beni-Suef city, Egypt. Antimony tin oxide (ATO)/polyaniline (PANI)/PbI(2) photoelectrode is prepared through the in situ oxidative polymerization of PANI on ATO, then PANI is used as an assistant for PbI(2) deposition using the ionic adsorption deposition method. The chemical structural, morphological, electrical, and optical properties of the composite are confirmed using different analytical tools such as X-ray diffreaction (XRD), scanning electron microscope (SEM), transmision electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. The prepared PbI(2) inside the composite has a crystal size of 33 nm (according to the peak at 12.8°) through the XRD analyses device. SEM and TEM confirm the hexagonal PbI(2) sheets embedded on the PANI nanopores surface. Moreover, the bandgap values are enhanced very much after the composite formation, in which the bandgap values for PANI and PANI/PbI(2) are 3 and 2.51 eV, respectively. The application of ATO/PANI/PbI(2) nanocomposite electrode for sewage splitting and H(2) generation is carried out through a three-electrode cell. The measurements carreid out using the electrocehical worksattion under th Xenon lamp (100 mW.cm(−2)). The produced current density (J(ph)) is 0.095 mA.cm(−2) at 100 mW.cm(−2) light illumination. The photoelectrode has high reproducibility and stability, in which and the number of H(2) moles is 6 µmole.h(−1).cm(−1). The photoelectrode response to different monochromatic light, in which the produced J(ph) decreases from 0.077 to 0.072 mA.cm(−2) with decreasing of the wavelengths from 390 to 636 nm, respectively. These values confirms the high response of the ATO/PANI/PbI(2) nanocomposite electrode for the light illuminaton and hydrogen genration under broad light region. The thermodynamic parameters: activation energy (Ea), enthalpy (ΔH*), and entropy (ΔS*) values are 7.33 kJ/mol, −4.7 kJ/mol, and 203.3 J/mol.K, respectively. The small values of ΔS* relted to the high sesnivity of the prepared elctrode for the water splitting and then the hydrogen gneration. Finally, a theoretical study was mentioned for calculation geometry, electrochemical, and thermochemistry properties of the polyaniline/PbI(2) nanocomposite as compared with that for the polyaniline.