Mixed Molten Salts Toward Advanced Nanomaterials – MOLTEN

This TREMPLIN project aims at supporting a future application to the ERC Consolidator call of a proposal which was evaluated favorably in 2016. The goal is to provide a proof-of-concept validating the feasability of the innovative approach sumitted to the ERC. The summary of the ERC project, called MOLTEN, is the following:

MOLTEN targets the emergence of a synthesis process to strongly widen the range of compounds reachable as nanoparticles, scarce compared to bulk phases known from usual approaches.

It focuses on boron-based inorganic phases, as transport and surface properties of reported bulk compounds suggest that nanoparticles will open novel avenues in energy conversion. Their synthesis performed at temperatures (T) above 1000°C yields large crystal growth. Hence these phases are uncharted at the nanoscale.

To reach nanoparticles, metastable states not accessible by solid state chemistry and known processes must be obtained. MOLTEN draws on liquid-phase syntheses and proposes 3 breakthroughs based on liquid ionic mixtures, made of inorganic molten salts at 300-1000°C, and inorganic and organic salts below 300°C:

1) Exploration of the T range up to 1000°C in liquids as a virgin field for colloidal syntheses. T lower than standard solid state processes provides conditions favorable to the discovery of novel metastable compounds;

2) Discovery of a parameter in liquid-phase syntheses enabled by ionic mixtures: adjusting the liquid mixture composition allows using biphasic media and tuning the solvating ability for enhanced precursor solubility;

3) Development of new strategies to ensure increased nucleation rates and limited crystal growth: high T microwave heating and quenching.

The first part (WP1) addresses boron carbon phosphides with dense structures, as the few known bulk compounds hint at a tremendous variety of unreported materials.

WP2 deals with boron and silicon-based inorganic clathrates and open frameworks, including compositions and structures never reported.

WP3 focuses on advanced characterization of the crystal structure and morphology, and of novel properties in thermoelectric conversion of waste heat and photocatalytic water splitting.

WP4 explores reaction mechanisms at play within this novel platform of nanomaterials synthesis through phase diagrams and in situ investigations.

The TREMPLIN strategy is to focus synthesis efforts on a single type of materials and a specific high impact application: silicon-based clathrate compounds for applications in thermal-to-electrical energy conversion, for the recovery of waste heat and impact on energy harnessing and environmental issues. This approach should provide a proof-of-concept of the novel synthetic strategy I want to develop in MOLTEN It will also build and establish my expertise on the chemistry of silicon-based nanomaterials.