Ossidi Nanostrutturati e Nanocompositi a base di Ti per Elettrolisi Fotoassistita (TOPSIS)

Responsabili di progetto

Chiara Ingrosso, Tamara Petkova

Accordo

BULGARIA - BAS - Bulgarian Academy of Sciences

Bando

CNR/BAS triennio 2019-2021 2019-2021

Dipartimento

Scienze chimiche e tecnologie dei materiali

Area tematica

Scienze chimiche e tecnologie dei materiali

Stato del progetto

Nuovo

Proposta di ricerca

TOPSIS focuses on the development and test of novel nanostructured photocatalysts towards solar light assisted electrolysis of water for the generation of H2 and O2. Worldwide researchers have focused on the development of renewable energy sources, to meet world's energy needs and address the environmental issues, in alternative to fossil and mineral fuels, hydroelectric and nuclear sources, responsible for global warning, emission of pollutants and CO2. Among the diverse renewable energy sources, hydrogen is a promising CO2-free clean energy carrier. Water is an affordable hydrogen source and its splitting provided by an external bias, while assisted by sunlight and photocatalysts, allows conversion of solar energy in clean H2 energy with high quantum conversion efficiency. [M. D. Bhatt et al. RSC Adv. 2017, 7, 34875]
In a typical photo-assisted electrolysis, holes generated at the photo-anode of the cell oxidize water to O2 or other oxygen containing species, while photogenerated electrons are transferred via an external circuit to the cathode, leading to H2 evolution. In a photoelectrochemical cell, large overpotentials occur at the photoanode, so an external bias should be applied for providing the overvoltage at the cathode, to sustain the current flow and increase the band bending of the semiconductor to maintain the charge separation [A.J. Nozik et al. J. Phys. Chem. 100 (1996) 13061].
Photo-assisted electrolysis hence requires a suited photocatalyst for the photo-anode, characterized by extended light harvesting capability and efficient exciton generation for a highly efficiency charge collection at the cell electrodes. At present, great effort focus on the development of efficient photo-anode materials towards systems for industrial production of photocatalytic H2 to be used as energy carrier. [M. D. Bhatt et al. RSC Adv. 2017, 7, 34875]
TiO2 based nanomaterials are among the most studied photocatalysts for photo-assisted water splitting [S. Chen Electrochem. Comm. 2016, 63, 10]. TiO2 nanostructures with different morphologies, such as nanotubes, nanowires arrays and nanoparticles (NPs), have been widely investigated because of their biocompatibility, chemical inertness, photostability and cheap production cost, which make them promising candidates for energy and environmental applications. The efficiency of TiO2 nanomaterials still needs to be further improved, for instance by doping the semiconductor with metal and nonmetal ions, in order to extend its optical absorption towards the visible spectral range and developing a photosensitive material, suited for visible light-driven water-splitting [Y. Cui et al. Chem. Mater. 2013, 25, 4215]. Another approach is based on the combination of TiO2 nanostructures and other functional materials, as carbon nanotubes and graphene sheets [Y. Zhou et al. New J. Chem. 2011, 35, 353]. The efficiency of such hybrid materials has demonstrated to highly increase compared to that of bare TiO2 nanostructures. Such an improvement is due to the combination of the intrinsic properties of the single components that leads to extended light adsorption range, enhanced charge separation, conductivity and charge collection at electrodes [Y. Zhou et al. New J. Chem. 2011, 35, 353].
Ternary oxide systems based on Ti have been also explored as new photocatalysts to improve the efficiency. In particular, perovskites-based photocatalysts have been studied, because of their promising photoactivity. Indeed, perovskite type compounds such as SrTiO3, K2La2Ti3O10, NaTaO3, and RbNdTa2O7 have been proven to be highly photoactive for water-splitting [J. K. Stolarczyk et al. ACS Catal. 2018, 8, 3602]. Unfortunately, their applications have been limited to the ultraviolet region, due to their large band gap (>3.0eV), that makes the material able to cover only about 4% of the solar spectrum.
The three-year TOPSIS project aims to synthesize and investigate highly functional and environmental friendly photocatalysts of diverse composition and morphology, based on innovative Ti based nanostructured materials, endowed by a long-lasting (photo)stability, for overcoming the intrinsic limitations of the currently available materials, used in photo-assisted water splitting and achieving light H2 energy conversion efficiency superior than those of state-of-art materials. We intend to prepare photosensitive nanostructured materials of different morphology and chemical composition, namely based on: i.) Reduced Graphene Oxide (RGO) surface decorated with TiO2 nanocrystals (NCs), ii.) nanocomposites based on TiO2 NPs and Au nanorods (NRs) and iii.) doped Ti nanoxides, synthesized by sustainable chemical routes, to test as photocatalysts in a photoelectrochemical cell.
The research on such a relevant topic requires a multi-disciplinary work, which will be successfully realized by a tight collaboration between Bulgarian IEES and the Italian chemist group of the CNR/IPCF. The activities will be carried out by combining in a synergistic approach, the complementary expertise of the partners, namely i) CNR-IPCF expert in the colloidal chemical synthesis and characterization of colloidal NPs/NCs, nanocomposites based on carbon nanostructures (i.e. graphene and carbon nanotubes) and colloidal NPs/NCs for photocatalytic and biomedical applications, optics and sensors, and ii) IEES expert in the synthesis of oxide and non-oxide nanocatalysts by sol-gel, hydrothermal routes, melt quenching, vacuum-thermal evaporation and pulsed laser deposition, and their (photo)electrochemical characterization for applications in fuel cells.
Such a study will aim at advance the knowledge in photocatalyst properties for photo-assisted water splitting and in the development of new synthetic strategies for efficient photocatalysts to be used in systems for H2 clean energy production.

Obiettivi della ricerca

The goal of TOPSIS project is the design and preparation, by different approaches, of UV- and UV-Vis-light photosensitive nanostructured materials having different composition and morphology, namely i.) doped Ti-based nanoxides, ii.) hybrid nanocomposites formed of large area RGO flakes, surface decorated with colloidal TiO2 NCs, and iii.) nanocomposites based on TiO2 NPs and Au NRs, to characterize photoelectrochemically for photocatalytic H2 evolution applications.
Such a farsighted objective answers to the need of implementing innovative strategies for the preparation of photocatalysts, highly performing in terms of light harvesting capability, exciton generation and separation, and charge collection at the electrodes, to be integrated at the photo-anode of fuel cells.
TOPSIS aims to advance in several scientific topics:
- design, preparation and characterization of (photo)stable and sustainable large surface area materials for photo-anodes;
- fabrication and characterization of robust and highly (photo)sensitive electrodes;
- (photo)electrochemical investigation of the prepared photocatalyst materials towards H2 evolution purpose.

Ultimo aggiornamento: 25/04/2024