Increased Pd Stability and Activity for Oxygen Reduction via Alloy of Early Transition Metals

Increased Pd Stability and Activity for Oxygen Reduction via Alloy of Early Transition Metals
PEMFC; ORR; Pd; Activity; Stability
Issue Date
2010 한국전기화학회 추계학술 발표회
, 65-65
A polymer electrolyte membrane fuel cell (PEMFC) is a promising altenative device to reduce our reliance on environmentally unfriendly fossil fuel. However, there are several problems that should be overcome to make PEMFC more economically attractive. One of the most pivotal issues of problems is considerable overpotential associated with the slow reaction rate of the oxygen reduction reaction (ORR; (l/2O2 + 2(H+ + e') -> H2O)) at the cathode. Other tremendous challenge is the stability for electrochemical reaction, including metal dissolution and surface oxide formation, which occurs intensely in acid medium (< pH 1) at high potential (> 0.8 V). In spite of the significant technological interest in finding active and stable catalyst for ORR condition, the direct experimental inspection of the contributions of the stability involving acdvity has rarely been investigated in electrochemkal reducdon of oxygen. Herein we report more active and stable electrocatalytic cathode materials consisting of Pd-based alloy involving late and early transition metals. In parucular, we focused on the electronic and lattice-strain effect of the Pd-Y alloys for the purpose of analyzing the activity. To clarify these effects, we introduced a correlation between the d-band structure of Pd induced by its electronic effect and the ORR activity, In addition, we investigated the stability on Pd-based binary alloy electrodes by applying the calculated heat of alloy formation closely relative to the degree of segregation, a descriptor for the stability of electrocatalysts. Our results show keys toward resolving serious problems to make PEMFC economically viable.
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