Enhancement of Platinum Cathode Catalysis by Addition of Transition Metals

109 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.In addition to overcoming the slow kinetics of the ORR, another critical issue to low temperature fuel cells is the gradual loss of performance due to the degradation of the cathode catalyst under the harsh operating conditions in fuel cells. In the second part of my study, the performance, stability, and durability of four different Pt-based cathode catalysts were investigated in a microfluidic hydrogen-oxygen (H2/O2) fuel cell platform with a flowing acidic electrolyte. The studied catalysts include Pt black, as-received unsupported commercial Pt3Co alloy nanoparticles, acid-treated Pt3Co (Pt3Co-at), and Mo-modified Pt 3Co nanoparticles (Pt3Co/Mo). The addition of Mo to the Pt 3Co nanoparticles was confirmed by XPS and electrochemical data. Adding Mo to Pt3Co nanoparticles does not alter the electronic effect of Co exerted on Pt, but significantly improved the performance and stability of the electrocatalyst. The binding energy of Pt 4f also demonstrated an upshift of 0.2 eV vs. that of pure Pt, similar to that of the nanoparticles without Mo. Here, a novel application of the rotating disk electrode was used to study the electrocatalytic activity of relevant electrocatalysts directly on gas diffusion electrodes, indicating an oxygen reduction activity of Pt3 Co/Mo which is slightly better than that of Pt3Co and Pt black. In terms of fuel cell performance, all the cathode catalysts showed good short-term stability and electroactivity. However, in accelerated aging studies, Pt3Co/Mo showed a superior improved long-term stability over 10,000 potential cycles in acidic solution over the other catalysts studied. This enhancement of Pt3Co/Mo was attributed as both enhanced catalytic stability and electrode durability via an electrochemical impedance spectroscopy study. Therefore, building on these promising results, further development of these catalysts may lead to significant performance enhancements.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD