Synthesis of metal oxide nanoparticles via a robust “solvent-deficient” method

Abstract

We report an efficient, general methodology for producing high-surface area metal oxide nanomaterials for a vast range of metal oxides, including at least one metal oxide nanomaterial from nearly every transition metal and semi-metal group in the periodic table (groups 3-4 and 6-15) as well as several from the lanthanide group (see ). The method requires only 2-3 simple steps; a hydrated metal salt (usually a nitrate or chloride salt) is ground with bicarbonate (usually NH4HCO3) for 10-30 minutes to form a precursor that is then either untreated or rinsed before being calcined at relatively low temperatures (220-550 °C) for 1-3 hours. The method is thus similar to surfactant-free aqueous methods such as co-precipitation but is unique in that no solvents are added. The resulting "solvent-deficient" environment has interesting and unique consequences, including increased crystallinity of the products over other aqueous methods and a mesoporous nature in the inevitable agglomerates. The products are chemically pure and phase pure with crystallites generally 3-30 nm in average size that aggregate into high surface area, mesoporous agglomerates 50-300 nm in size that would be useful for catalyst and gas sensing applications. The versatility of products and efficiency of the method lend its unique potential for improving the industrial viability of a broad family of useful metal oxide nanomaterials. In this paper, we outline the methodology of the solvent-deficient method using our understanding of its mechanism, and we describe the range and quality of nanomaterials it has produced thus far.

Highly Active Mesoporous Cu−Al2O3 Catalyst for the Hydrodeoxygenation of Furfural to 2‐methylfuran

“…In particular, we have studied Al 2 O 3 as a support because it is one of the most commonly used supports in the corporate world. Therefore, our interest is focused on the introduction of Cu for its selectivity toward the aldehyde group of FUR and the addition of alumina for its large surface area and moderate acidity…”

“…On the other hand, an unambiguous difference in the BET surface area ( S BET ) and pore volume ( V pore ) was observed. The largest S BET (407 m 2 g −1 ) and V pore (0.53 cm 3 g −1 ) values were observed for m20CA, due to the formation of NH 4 NO 3 during synthesis that can subsequently serve as a spacer . Moreover, it contributes to the narrowest BJH pore size distribution as well as the exceptional N 2 adsorption (Figure S2).…”

“…Catalyst preparation : We modified the solvent‐deficient precipitation method reported by Smith et al . to synthesize mesoporous Cu−Al 2 O 3 .…”

Solvent‐deficient method lowers grain‐boundary resistivity of doped ceria

“…Methods like spray pyrolysis, sol‐gel process and hydrothermal synthesis have been previously developed for the preparation of nanometer size rare earth‐doped ceria with various morphologies . Recently, a novel technique to synthesize nanoparticles without a liquid solvent known as solvent‐deficient method (SDM) has been developed . The various oxides of transition metals, semi‐metals, lanthanides, as well as complex oxides have been successfully synthesized using SDM .…”

Thermodynamics of Fe3O4–Co3O4and Fe3O4–Mn3O4spinel solid solutions at the bulk and nanoscale

“…The activity -composition relations in ternary solid solutions have been determined using electrochemical measurements and attempts were made to obtain enthalpies and entropies of mixing from the temperature dependence of EMF and other studies 23,24 Despite these earlier studies, separating the effects of enthalpy and entropy on the Gibbs energy of mixing in these complex solid solutions is difficult without independent calorimetric measurements of the enthalpy of mixing, which has only been done for the bulk Mn 3 Previous investigations suggest a number of spinel phases have lower surface energy than other oxides of the same metal 32 and it seems probable that this behavior can be extended to the transition metal spinel solid solutions. 37 All the bulk phase samples were prepared by calcining the corresponding nanocrystalline phase in a vacuum furnace at elevated temperatures for 24 h. The goal of the present investigation is to obtain a systematic picture of mixing properties in Fe, Co, Mn spinels at macroscopic and nano scales.…”