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Extended Two Dimensional Nanotube and Nanowire Surfaces as Fuel Cell Catalysts

  • Author(s): Alia, Shaun Michael
  • Advisor(s): Yan, Yushan
  • Kisailus, David
  • et al.
Abstract

Extended network nanomaterials of platinum (Pt), silver (Ag), palladium (Pd), and gold (Au) are synthesized and characterized as proton exchange membrane (PEMFC), hydroxide exchange membrane (HEMFC), and direct alcohol (DAFC) fuel cell catalysts.

Porous Pt nanotubes (PPtNTs), 5 nm thick, are synthesized by the galvanic displacement of Ag nanowires (AgNWs) for PEMFCs and DAFCs. PPtNTs produce oxygen reduction (ORR) and durability characteristics significantly higher than supported Pt nanoparticles (Pt/C); prior to and following durability testing, PPtNTs produce specific ORR activities 3.1 and 19.9 times greater than Pt/C. The methanol oxidation peak specific activity of PPtNTs is 2.0 times and 1.3 times greater than Pt/C and a polycrystalline Pt electrode.

AgNWs, 25-60 nm in diameter, are synthesized as HEMFC catalysts. In contrast to Ag nanoparticles, the ORR specific activity of AgNWs increases and peroxide production decreases with diameter reduction. AgNWs (25 nm) exceed the mass and specific ORR activity of 2.4 nm AgNPs by 16 % and 5.3 times.

Pd and Au NTs, 5 nm thick, are synthesized as HEFMC and DAFC catalysts. PdNTs and AuNTs exceed the ORR specific activity of Pt/C by 42% and 21%. PdNTs produce an earlier onset potential than all conventional catalysts in methanol and ethylene glycol oxidation; PdNTs further meet or exceed the specific activity of Pt/C in methanol, ethanol, and ethylene glycol oxidation.

Pt coated PdNTs (Pt/PdNTs) are synthesized as PEMFC catalysts by the incomplete galvanic displacement of PdNTs. Pt/PdNTs express an ORR activity comparable to PtNTs while containing 9-18 wt% Pt. Pt/PdNTs exceed the cost and specific activity benchmarks of the US Department of Energy (DOE) and produce a Pt normalized mass activity 11.6 times greater than Pt/C.

Pt coated copper NWs (Pt/CuNWs) are synthesized by the incomplete galvanic displacement of copper nanowires. Pt/CuNWs exceed the cost and specific activity DOE benchmarks; durability testing reveals improved retention of surface area and ORR activity in comparison to Pt/C.

Templated synthesis allows for the control of growth directions and lattice spacing. The use of templated extended network nanomaterials has improved the electrocatalytic activity and durability of conventional fuel cell catalysts.

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