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Nanomaterials

Microfluidics offer a mild route to metal-carbide nanoparticles

Low-temperature solution-phase synthesis could enable use of the inexpensive materials as industrial catalysts

by Mitch Jacoby
January 9, 2020 | APPEARED IN VOLUME 98, ISSUE 2

 

09802-scicon2-carbide.jpg
Credit: Richard L. Brutchey/USC
Molybdenum carbide nanoparticles (Mo = blue; C = gray), which can convert CO2 to CO, methane, and ethane (shown above), can now be made via a mild solution-phase route.

A mild solution-phase process for making transition-metal carbides could help the low-cost materials replace expensive noble-metal catalysts in some industrial processes (J. Am. Chem. Soc. 2020, DOI: 10.1021/jacs.9b11238).

Nanoparticles of transition-metal carbides are known to be active catalysts that can convert carbon dioxide to carbon monoxide, hydrocarbons, and other valuable compounds. The carbides are usually prepared via carburization, a process in which metals or metal oxides are heated in a furnace together with a carbon source and hydrogen, sometimes at temperatures above 800 °C. Because the harsh conditions make it difficult to control particle size and morphology, which affect catalytic performance, carbides are rarely used as catalysts. In addition, unlike metal and semiconductor nanoparticles, which can be made with exquisite control thanks to years of intense research, metal carbides are rarely studied.

Noah Malmstadt and Richard L. Brutchey of the University of Southern California and coworkers searched for ways to make metal-carbide nanoparticles under mild conditions. The team came up with a solution-phase flow process that converts molybdenum hexacarbonyl to phase-pure molybdenum carbide at roughly 100 °C. Preliminary tests show that the nanoparticle carbides are twice as active and twice as selective as bulk carbides in converting CO2 to C2 products like ethane.

Wayne State University’s Stephanie L. Brock, a specialist in nanomaterials, says, “This work is impressive because it shows how continuous microfluidic synthesis can produce materials that are virtually impossible to prepare otherwise by solution-phase methods in a scalable manner.”

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