■ Title : Development of electrocatalysts in solid acid fuel cells
■ Speaker : Dr. Haemin Paik
Materials Science and Engineering, Massachusetts Institute of Technology
■ Date and time : 11/04 (Mon) 5:00 ~ 6:00 PM
■ Venue : Applied Engineering Building (W1-1), Room #2429
■ Host : Prof. WooChul Jung
■ Abstract : Solid acid fuel cells (SAFCs) based on the proton-conductive electrolyte CsH2PO4 (CDP) have shown promising power densities at an intermediate operating temperature. However, Pt loadings in SAFCs remain higher than desirable, and few alternatives to Pt have emerged for either the hydrogen oxidation reaction or the oxygen reduction reaction in SAFCs. In this talk, I will talk about the use of Pd and Pd-based alloys for electrocatalysis in SAFCs.
To evaluate Pd as a SAFC anode, both catalytic activity for hydrogen electro-oxidation and reactivity with the CDP electrolyte are studied. It is found that Pd reacts with CDP, forming palladium phosphide (Pd-P) at the metal-electrolyte interface. With the aim studying the behavior of Pd in the absence of this reactivity, Pd overlain on Pt was examined in a bilayer geometry. The bilayer Pt|Pd films showed much higher activity for hydrogen electro-oxidation than films of Pt alone, as measured by AC impedance spectroscopy. Ex situ analysis revealed that Pd diffused into the Pt layer under operating conditions. The extremely high activity of the interdiffused films suggest that Pd catalyzes reactions at both the metal-gas and metal-electrolyte interfaces, and furthermore facilitates rapid hydrogen diffusion rates through the films. The high activity of Pt|Pd films, in which Pd eventually contacts the underlying electrolyte due to interdiffusion of the metals, motivated an investigation of Pd-based catalysts (Pd and Pd-P). The hydrogen oxidation kinetics from Pd, and Pd-P were observed to be comparable and more effective than the equivalent mole percent of Pt supported on carbon.