Photoelectrochemical Solar Cells Prepared from Nanoscale Zerovalent Iron Used for Aqueous Cd²⁺ Removal

Nanoscale zerovalent iron (nZVI) particles have been widely studied in the environmental sciences for wastewater treatment. These types of nanoparticles react in aqueous media producing metal oxides, which can be photoactive in the ultraviolet energy region. This prompted us to examine alternatives for the preparation of nanomaterials using nZVI in the presence of 6 and 30 ppm of Cd²⁺ in aqueous solutions. These Cd²⁺ concentrations are representative of contaminated regions of Puerto Rico such as the Las Cucharillas Marsh in Cataño. Comprehensive chemical and physical characterization of the resulting nZVI products after their exposure to Cd²⁺ was done. Further studies of the resulting nanostructures were completed using a photoelectrochemical solar cell (PSC) as the photoanode material. Incident photon-to-current efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) analysis of these PSCs showed active photochemical properties in the ultraviolet range for the sample exposed to 30 ppm of Cd²⁺. Changes in the structure and chemical oxidation states of the species were observed in transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy analysis was attributed to these photochemical properties. These results show an alternative synthetic method for producing iron oxides for photocatalytic applications, and a possible strategy for reuse of nZVI after water remediation treatments.