Development of photoelectrodes based on perovskite materials and copper, copper-iron oxides for solar fuels production

In recent years, the production of the so-called “solar fuels” has garnered significant attention in the energy and environmental fields due to the need of decarbonizing our society. Renewable energies such as solar power play a crucial role in this, along with the development of new and highly efficient materials. Within this context, the present thesis focuses on synthesizing different kinds of materials and optimizing innovative deposition processes to produce hydrogen, ammonia (as a hydrogen carrier), and to drive carbon dioxide reduction reactions (CO2RR) using a specific technology: a photo-electrochemical cell (PEC). Inorganic halide perovskites like CsPbBr3 and CsPbI3, Aurivillius-type perovskites such as BiFeO3 (BFO), and double oxide perovskites like CaCu3Ti4O12 (CCTO) were investigated for storing hydrogen into ammonia molecules (N2RR). Concurrently, copper-based (CuO, Cu2O) and copper–iron-based (CuFe2O4, CuFeO2) systems were tested for hydrogen production via water splitting or CO2RR, primarily focusing on developing and optimizing innovative processes. After synthesis, these materials underwent comprehensive characterization to determine their functional properties. BFO, CCTO, copper, and copper-iron powders were subsequently processed to produce screen-printed photoelectrodes, and the influence of their film thicknesses on photo-electrochemical properties was determined. Since the CsPbBr3 and CsPbI3 systems obtained as colloidal suspensions were used to prepare a thin film by spin coating, a graphitic layer, deposited by sputtering, was employed to protect them from the water environment. After that, the properties of the as-obtained photoelectrodes were enhanced using catalytic materials (metallic, organic, and oxide) by surface decoration with inkjet printing and the formation of heterostructures. All films obtained were thoroughly characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and UV–Visible spectroscopy. Electrochemical and photoelectrochemical analyses were conducted in a suitable electrolyte for the final application under both dark and different illumination conditions, including electrochemical impedance spectroscopy, Mott–Schottky analysis, linear sweep voltammetry, and chronoamperometry. Finally, photo-electrocatalytic tests were done in a single chamber PEC, and the obtained liquids and gas products were analyzed by colorimetric method (for N2RR), gas chromatography (hydrogen production and CO2RR), and by NMR1. The obtained results showed that all systems tested were able to drive the desired reactions as indicated by product yields and faradic efficiencies. In this way, the structural and photoelectrochemical properties were linked to the final functional ones. The obtained results highlight the importance of the properties of perovskite materials and metal oxide ones in combination to deposition process optimization to achieve new and efficient photoelectrodes to produce solar fuels.