PNRR per la Missione 4, Componente 2, Investimento 1.1 - Avviso 104/2022 - Prot. 2022474YE8 - CUP J53D23007340008 - Finanziato dall'Unione Europea Next Generation EU

Sustainable human activities call for efficient devices converting renewable energies (e.g. sunlight) to fuels such as H₂. A very promising approach is photoelectrochemical water splitting: electron/hole pairs generated at two photoelectrodes (PE) drive the half-reactions producing H₂ and O₂. The state of the art PE built with ternary metal oxides (TMOs) like CuFe₂O₄ face major limitations like scant efficiency, photocorrosion and instability. They are ascribed to the low charge transfer induced by the small polarons due to the TMO hybrid valence band orbitals, and to the high recombination rate of charge carriers at the TMO surface and bulk states. Moreover, the current PE synthesis methods hinder a comprehensive investigation of different TMO phases, stoichiometries and transport properties for sizes below 50 nm.

The project strategy is to overcome the current limits by:

1. reducing the TMO sizes by producing PE of ZnFe₂O₄, CuFe₂O₄ and BiFeO₃ with a nanogranular morphology (NG-TMO) at scales below 50 nm by supersonic cluster beam deposition (SCBD);
2. determining the PE morphological, optical and electrochemical behavior for three different NG-TMO compounds;
3. determining the PE transport behavior from the reaction kinetic constants (kt for the hopping process and kr for recombination process), as a function of TMO selected stoichiometries, phases and sizes;
4. delivering libraries of NG-TMOs for rapid investigation thanks to the SCBD high throughput;
5. delivering stable and efficient PE thanks to the acquired knowledge and the SCBD capabilities.

The project breakthroughs are:

1. a new class of nanostructured PE for electrochemistry, NG-TMOs;
2. morphological, optical and stoichiometric properties correlation with PE thickness and annealing temperature;
3. electrochemical properties correlation with the PE thickness and annealing temperature;
4. charge transport correlation with morphology, optical response, stoichiometry;
5. reveal the role of small polarons and surface recombination in NG-TMOs at scales below 50 nm;
6. libraries of NG-TMO PE.

Two experienced research units will perform complementary physical and electrochemical characterizations of the PE. The SCBD synthesis capability will allow the units to work in parallell, exploiting two persons at the post-doctoral level fully dedicated to the project.

Working group:

• Luca Gavioli - Responsabile scientifico UCSC
• Skerxho Osmani
• Michele Vergari

Partners:

• Università degli Studi di Padova