Creating a better catalyst may be as simple as letting a virus do the construction for you. Angela Belcher and coworkers at MIT have used the M13 bacteriophage as a template for growing nanoparticles and nanowires of rhodium and nickel on ceria—a catalyst that can convert ethanol to hydrogen and is therefore promising for fuel cells (ACS Nano, DOI: 10.1021/nn100346h). The virus-templated catalyst possesses significantly different physical properties from catalysts of identical composition grown without the M13 bacteriophage, the researchers report, including improved long-term stability and less vulnerability to surface deactivation.
The M13 bacteriophage can be engineered to assemble nanowires by modifying its surface proteins, which nucleate myriad materials. In the past, Belcher’s group conscripted M13 to make battery electrodes as well as semiconducting and magnetic nanowires.
“The virus is relatively stiff and has a high aspect ratio, so it forms stunning open and porous nanostructures which increase the surface area and shift the pore size distribution,” explains Brian Neltner, the report’s first author. “Surface area and pore size distribution are critical aspects of catalysts, and can improve the reaction rates and selectivity.”
The researchers also found they could eliminate expensive rhodium from the biotemplated material, creating a catalyst with just nickel on ceria. This material can catalytically reform ethanol at temperatures around 400 °C, “offering an alternative, inexpensive catalyst when higher temperatures are acceptable,” they write.
“This new approach to catalyst synthesis clearly provides desirable alternative possibilities for catalytic process applications,” comments Galen Stucky, a chemistry professor at the University of California, Santa Barbara.
“As a materials scientist, it amazes me every day that biology is able to produce a protein which will bind to or nucleate almost any arbitrary material,” Neltner says. “Our lab’s track record of success producing nearly anything we want to make with M13 I think speaks very highly of the incredible versatility of biological systems.”