Section: Complex Oxides

Nanoparticles

The nanoparticle synthesis efforts at EMC2 mostly take place in the Frank DiSalvo group, and focus on preparing useful fuel cell electrocatalysts in nanoparticle form.  The research groups in EMC2 (formerly the Cornell Fuel Cell Institute) have discovered that bulk ordered intermetallic compounds- a class of solid materials that are made of multiple metals, but are not random alloys- show impressive resistance to poisoning as anode catalysts, and amazing activity for formic acid oxidation. 

To keep the fuel cell's weight to a manageable level, and have as low a loading as possible of (usually) expensive metals, the electrocatalysts must be prepared as nanoparticles.  The overall goal of the DiSalvo group's nanoparticle activities is to develop the synthetic skills necessary to be able to choose any target metal composition (with control of the metals' identities, ratio to each other, and crystal phase), and prepare that composition as homogeneous nanoparticles.

Fig 1. The particles that we are able to make are only a few nanometers (billionths of a meter) wide. Much more current is generated for oxidizing formic acid fuel using PtPb catalyst (blue lines) than on other known catalysts.

Also, high-throughput thin-film catalyst searches in the Bruce van Dover group have yielded interesting multimetallic compositions (both intermetallic and alloy) that show enhanced electrocatalytic activity for fuel oxidation and oxygen reduction.  However, those thin-film compositions must also be prepared as nanoparticles for use in a real fuel cell. 

Right now we're working on synthesizing ordered intermetallic phases between platinum and first row transition metals, as well as some other compounds.  By altering metal precursor, solvent, and reducing agent, we can build an understanding of what conditions allow formation of an ordered intermetallic, and what may impair it.  Then we can see if these are useful electrocatalysts, and how synthesis may methods change that activity.

We're also starting work on preparing nanoparticles out of a novel thin film alloy discovered in the van Dover group.  We've found that preparing a Pd alloy with two other transition metals is better for oxygen reduction than Pd alone or Pd with only one of those metals.  The greatest goal for this is to synthesize an electrocatalyst that can beat Pt for oxygen reduction activity.

Many exotic metal combinations have been prepared and screened as catalysts.  None of them are perfect, but we’re learning more every day!