Deep eutectic-solvothermal synthesis of nanostructured ceria

Abstract

Ceria is a technologically important material with applications in catalysis, emissions control and solid-oxide fuel cells. Nanostructured ceria becomes profoundly more active due to its enhanced surface area to volume ratio, reactive surface oxygen vacancy concentration and superior oxygen storage capacity. Here we report the synthesis of nanostructured ceria using the green Deep Eutectic Solvent reline, which allows morphology and porosity control in one of the less energy-intensive routes reported to date. Using wide Q-range liquid-phase neutron diffraction, we elucidate the mechanism of reaction at a molecular scale at considerably milder conditions than the conventional hydrothermal synthetic routes. The reline solvent plays the role of a latent supramolecular catalyst where the increase in reaction rate from solvent-driven pre-organization of the reactants is most significant. This fundamental understanding of deep eutectic-solvothermal methodology will enable future developments in low-temperature synthesis of nanostructured ceria, facilitating its large-scale manufacturing using green, economic, non-toxic solvents.

The Effect of Water upon Deep Eutectic Solvent Nanostructure: An Unusual Transition from Ionic Mixture to Aqueous Solution

“…The physicochemical properties of DESs are related to those of ionic liquids and their mixtures; DESs are hybrid systems where molecular ionic clusters are found within a complex and disordered hydrogen‐bonding network . This nanostructure can be adjusted by selection of the mixing ratio and molecular chemical moieties, and this additional degree of design freedom has aided the development of DESs as “greener” alternative media for organic and inorganic synthesis, electrochemistry, separation, extraction, and biotransformations …”

Hydrophobic Deep Eutectic Solvents Incorporating Trioctylphosphine Oxide: Advanced Liquid Extractants

“…The term Deep Eutectic Solvent (DES) [1][2][3] is most commonly used to describe low melting liquids formed by combining organic salts such as choline chloride with urea or other hydrogen-bond donor components including carboxylic acids and alcohols. DES were initially popularised 4 as lower cost and more environmentally benign (greener) variants of non-volatile ionic liquids and have been used as non-aqueous electrolyte solutions, 5 and media for nanoparticle and materials synthesis, [6][7][8][9] solvents for catalysis 10 and as vehicles for delivery of active pharmaceutical ingredients 11,12 have been extensively investigated in recent years.…”

The Effect of Water upon Deep Eutectic Solvent Nanostructure: An Unusual Transition from Ionic Mixture to Aqueous Solution

“…The physicochemical properties of DESs are related to those of ionic liquids and their mixtures;2 DESs are hybrid systems where molecular ionic clusters are found within a complex and disordered hydrogen‐bonding network 3. This nanostructure can be adjusted by selection of the mixing ratio and molecular chemical moieties,4 and this additional degree of design freedom has aided the development of DESs as “greener” alternative media for organic and inorganic synthesis,5 electrochemistry, separation, extraction, and biotransformations 6…”

“…[1] Thep hysicochemical properties of DESs are related to those of ionic liquids and their mixtures; [2] DESs are hybrid systems where molecular ionic clusters are found within ac omplex and disordered hydrogen-bonding network. [3] This nanostructure can be adjusted by selection of the mixing ratio and molecular chemical moieties, [4] and this additional degree of design freedom has aided the development of DESs as "greener" alternative media for organic and inorganic synthesis, [5] electrochemistry,s eparation, extraction, and biotransformations. [6] DESs are made of coordinating, hydrogen-bonding ions and molecules,m aking them strongly water-miscible and hygroscopic.L atent absorbed water is unavoidable,a nd impacts upon the physicochemical properties of DESs,s uch as the melting point, with inadequate characterization leading to poor reproducibility.…”