Gas-diffusion electrocrystallization (GDEx), a new electrochemical process that we have developed, allows the synthesis of crystalline nanomaterials with well controlled and narrowly distributed properties that relate to specific functionalities. Gas-diffusion electrocrystallization is a one-pot rapid process involving a porous cathode with surface functionalities, an aqueous electrolyte containing metal or metalloid ions, and an oxidant gas, in which colloidal dispersions of nanomaterials or solid nanoparticles are synthesized. The general principles and mechanism through which GDEx operates will be introduced. Furthermore, examples of nanomaterials we have produced and their functionality or industrial relevance will be disclosed.
For instance, cerium oxide nanoparticles with controlled crystallite sizes in the range of 2 to 10 nm as well as varying content of Ce3+ and Ce4+ sites, which result in different degrees of oxygen sorption capacities and kinetics were synthesized using GDEx. Due to this feature, these cerium oxide particles can be tailored for pro-oxidant or anti-oxidant applications of interest for electronic packaging, oxidative stress alleviation, or cancer therapy. Likewise, lanthanum carbonate hydroxides formed by GDEx may find a niche as phosphate scavengers.
GDEx was also used to produce iron oxide nanoparticles in the range of 40 to 100 nm in which the ratio of heamatite (Fe2O3) and magnetite (Fe3O4) can be tweaked, providing the possibility to regulate their magnetic susceptibility. These materials are studied for molecular diagnostics. Solid nanoparticles of herbertsmithite, have been obtained through GDEx when applied to electrolytes containing Cu2+, Zn2+ and Cl– ions, by manipulating the redox potential. These Cu/Zn-based nanoparticles may have applications in data storage, high-temperature superconductors and for so-called ‘‘quantum-entangled’’ batteries.
Finally, when operating GDEx with Mn(III/IV), compositions with birnessite and hausmannite—which may intercalate water and alkali metals— were synthesized, providing promising materials for batteries electrodes or catalysts.
In conclusion, GDEx is revealed as a new route to synthesize a wide range of nanoparticles, flexibly and with versatile control of composition, morphology, and physicochemical parameters such as crystallite size, lattice parameter and particle size, which in turn tailor specific functionalities.
The authors acknowledge the grant from the Flemish SIM MaRes programme for SBO project Get-A-Met.