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Nitride Stabilized Core-Shell Nanoparticles

Brookhaven National Laboratory

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(A) Comparison of surface strain versus predicted binding energy of oxygen (BE-O) on the Pt<sub>2</sub>MLNi<sub>4</sub>N and Pt nanoparticle models with ~1.7 nm. (B) Pt specific activity against BE-O on PtNiN/C and Pt/C. (C) Schematic of the inner Pt diffusion process to the defective sites at the vertex during cycling in the electrolyte. For clarity, the inner Pt atoms involved in diffusion are described in green, while the defects are in yellow.<br type="_moz" />

(A) Comparison of surface strain versus predicted binding energy of oxygen (BE-O) on the Pt2MLNi4N and Pt nanoparticle models with ~1.7 nm. (B) Pt specific activity against BE-O on PtNiN/C and Pt/C. (C) Schematic of the inner Pt diffusion process to the defective sites at the vertex during cycling in the electrolyte. For clarity, the inner Pt atoms involved in diffusion are described in green, while the defects are in yellow.

Technology Marketing Summary

Polymer electrolyte membrane (PEM) fuel cells offer exciting possibilities as alternative energy sources. The limiting reaction in these fuel cells is the oxygen reduction reaction (ORR) for which platinum is the best catalyst. Great strides have been made in reducing the overall amount of Pt required, and thus reducing the cost of the fuel cell, by coating a base metal nanoparticle core with a monolayer shell of Pt. Nevertheless, under voltage cycling conditions, as would be found in start-stop driving in a fuel cell electric vehicle, the core can dissolve, leaving the Pt shell vulnerable to dissolution itself. This invention addresses the challenge by stabilizing the core material against dissolution in the extremely acidic environment of a PEM fuel cell. During accelerated testing the stabilized core-shell nanocatalysts showed minimal (11mV) loss in half-wave potential over 35,000 cycles. The nanocatalysts also showed higher mass and specific activity than commercially available Pt/carbon catalysts.

Description

Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous shell with a nitride-stabilized metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble-metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with an ultrathin shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

Benefits

This invention addresses the dissolution of Pt during start-stop driving conditions by stabilizing the core material in the extremely acidic environment of a PEM fuel cell. During accelerated testing the stabilized core-shell nanocatalysts showed minimal (11mV) loss in half-wave potential over 35,000 cycles. The nanocatalysts also showed higher mass and specific activity than commercially available Pt/carbon catalysts.

Applications and Industries

The first area of application of this technology will probably in fuel cells for electric and hybrid-electric vehicles. Fuel cells are also used for stationary applications such as backup power for telecommunications and combined heat and power systems.

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Application 20150147682
Application
20150147682
Nitride Stabilized Core/Shell Nanoparticles
Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.
Brookhaven National Laboratory 11/26/2014
Filed
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
BSA 13-25PrototypeAvailable03/30/201503/30/2015

Contact BNL About This Technology

To: Poornima Upadhya<pupadhya@bnl.gov>