Au-Pd-Pt Multilayer Catalyst for Miniature Fuel Cells

Wednesday, 4 October 2017: 11:40
Chesapeake H (Gaylord National Resort and Convention Center)
R. Shirai (Tokyo University of Science), N. Vasiljevic (School of Physics, University of Bristol), and M. Hayase (Tokyo University of Science)
We have developed miniature fuel cells with monolithically fabricated Si electrodes. In the fuel cells, two Si electrodes with porous Pt catalyst layer, which Pt usage was 3.6mg/cm2, were hot-pressed onto either side of a PEM (polymer electrolyte membrane), and the prototype fuel cells showed promising performances of over 500mW/cm2 output at 313K with H2-O2. However, recent improvements of Li-ion battery are lowering expectation to the miniature fuel cells. The advantage of the fuel cell, i.e. clean and efficient energy source, should be strengthened.

Bio-mass is an ultimate energy source. Hydrogen can be produced by gasification of the bio-mass in reducing environment, but high CO concentration in the bio-mass derived hydrogen is inevitable. Catalyst poisoning by CO is problematic. We found that our Pd-Pt catalyst obtained by using UPD-SLRR had promising feature. Though the catalyst layer used only 6μg/cm2 of Pt, high tolerance to CO was observed. But Pd and Pt are rare metals, and both amounts should be minimized. In this study, a novel Au-Pd-Pt multilayer catalyst is proposed. Though Au is also a precious metal, reserve of Au is much larger than Pd and Pt, and porous Au can be formed on a Si substrate by similar process to porous Pt.

There is no clear evidence, but it is assumed that high CO tolerance of the Pd-Pt catalyst is realized with sub-monolayer Pt on Pd. Hydrogen absorption or stress near the interface between Pd and Pt are sensitive to the number of atomic layer of Pd, and fine control of Pd and Pt deposition on Au is crucial. In our previous study, sub-monolayer Pt was deposited with Cu-UPD, but hydrogen also absorbs on some metal surfaces and form atomic monolayer at slightly under the equilibrium potential. The H-UPD-SLRR can be performed just in an acidic plating bath containing Pd2+ or Pt4+. There is no need to replace the plating bath, and repetition of the atomic layer deposition process will be easy. In this study, basic fabrication strategy of the Au-Pd-Pt multilayer catalyst using H-UPD-SLRR process was examined using Au wire. Preliminary results of cyclic voltammetry suggested that Pd and Pt were successfully deposited on Au wire, and only one Pt deposition cycle on the Au wire with Pd, deposited by several UPD-SLRR cycles, showed large hysteresis loop in the CV, which related to catalytic performance.