QuantumSphere Nanoparticle Alloys Form High Power, Low Cost Catalysts for Fuel Cells and Sensors

Nanoparticle alloys for use as catalysts have been developed to replace platinum in fuel cells.  The catalysts can provide higher power for lower costs.

In U.S. Patent Application 20100069228, Quantumsphere, Inc. (Santa Clara, CA) details compositions useful in electrodes that provide higher power capability through the use of nanoparticle catalysts present in the composition. Nanoparticles of transition metals are preferred such as manganese, nickel, cobalt, iron, palladium, ruthenium, gold, silver, and lead, as well as alloys and their respective oxides.

These nanoparticle catalysts can substantially replace or eliminate platinum as a catalyst for certain electrochemical reactions. Electrodes, used as anodes, cathodes, or both, using such catalysts have applications relating to metal-air batteries, hydrogen fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), direct oxidation fuel cells (DOFCs), and other air or oxygen breathing electrochemical systems as well as some liquid diffusion electrodes according to inventors Robert Brian Dopp,  Kimberly McGrath and R. Douglas Carpenter

The number of atoms comprising a nanoparticle rapidly increases as nanoparticle size increases from ones to hundreds of nanometers. Roughly, the number of atoms increases as a function of the cube of the particle's effective diameter. Nickel nanoparticles, for example, have about 34 atoms in a 1 nm particle, about 34 million atoms in a 100 nm particle, and about 34 billion in a 1 micron particle. 

FIG. 1 is a transmission electron microscopy (TEM) photograph of nickel nanoparticles comprising an oxide shell, prepared by QuantumSphere, illustrating size uniformity of the nanoparticles. Some of the illustrated nanoparticles are generally spherical with diameters of just a few hundred atoms

Electrodes using QuantumSphere nanoparticle catalysts are also useful as sensors, for example, in electrochemical hydrogen sensors. The superior catalytic activity of certain embodiments of the electrode provides good sensitivity. The electrode comprises a nanoparticulate catalyst tailored to the desired application, for example, nickel, palladium, rhodium, or platinum for a hydrogen sensor. The electrodes are useful in sensors for other electrochemically active species, for example, oxygen in a reducing environment. Moreover, some embodiments are useful for detecting electrochemically active species in a liquid phase, for example, in water testing.

For testing in fuel cells, the mid-Tafel plot closed circuit voltages (CCVs) at 10 mA/cm² was chosen as the conditions for routine comparison since this region is predominantly electrochemically driven with little impedance interaction. The cathode is held for 30 minutes at 10 mA/cm² to ensure steady state. Experimentally, this value is stable for over 5 ampere-hours with little degradation.

Table 1, below, provides a summary of experimental data sorted by (CCV) on 10 mA/cm² test. Also tabulated is the loading of platinum or nanoparticle catalyst. The last column expresses the CCV as a percentage of the pure platinum catalyst, deconstructing the activities of nNiCo, nNi and nAg, as well as the augmenting effects of platinum and magnesium base catalysts. All of the nanoparticles comprised an oxide of the metal or metal alloy. The small n designates nano sized particles.

QuantumSphere electrodes can provide alternatives to platinum electrodes for use in diffusion cathodes for power production through the electrochemical reduction of oxygen. Such oxygen consuming cathodes exhibit numerous advantages, including high current output, high discharge voltage, and/or high current densities. 

 In some manufacturing embodiments, rollers in a roller mill are adjusted to just touching each other with a zero gap (e.g., "kissing"), and a catalyst sheet is formed between them.  A compressed mixture of nanocatalysts are then formed as a sheet or ribbon, which can be used to construct an alkaline fuel cell electrode by pressure lamination to a nickel current collector, or into PEMFC or DMFC cathodes through other processes. In some embodiments, a free-standing sheet can be made by milling the mixture in a roller mill, or by applying the mixture to roller nips in a roller mill.  The term "compressed mixture" refers to a self-adhering, shape-maintaining structure that is not necessarily without voids

QuantumSphere, Inc. (QSI) leverages its award winning advanced catalyst materials and process chemistry expertise to develop, manufacture, and license solutions for a broad range of portable power and clean-tech applications. The company's proprietary products, available in commercial volume, are used by industry leading companies to lower costs and enable breakthrough performance in established multi-billion dollar and high-growth markets such as batteries and fuel cells for portable power, emissions reduction for transportation and stationary power applications, and chemical synthesis of ammonia for food production. 

QuantumSphere, Inc.
2905 Tech Center Drive
Santa Ana, CA 92705

www.qsinano.com.