Gold–Palladium Bimetallic Catalyst Stability: Consequences for Hydrogen Peroxide Selectivity

5 years ago

Gold–Palladium Bimetallic Catalyst Stability: Consequences for Hydrogen Peroxide Selectivity

Serhiy Cherevko, Graham J. Hutchings, Christian H. Liebscher, Sriram Venkatesan, Karl J. J. Mayrhofer, Gerhard Dehm, Simon J. Freakley, Enrico Pizzutilo

During application, electrocatalysts are exposed to harsh electrochemical conditions, which can induce degradation. This work addresses the degradation of AuPd bimetallic catalysts used for the electrocatalytic production of hydrogen peroxide (H₂O₂) by the oxygen reduction reaction (ORR). Potential-dependent changes in the AuPd surface composition occur because the two metals have different dissolution onset potentials, resulting in catalyst dealloying. Using a scanning flow cell (SFC) with an inductively coupled plasma mass spectrometer (ICP-MS), simultaneous Pd and/or Au dissolution can be observed. Thereafter, three accelerated degradation protocols (ADPs), simulating different dissolution regimes, are employed to study the catalyst structure degradation on the nanoscale with identical location (IL) TEM. When only Pd or both Au and Pd dissolve, the composition changes rapidly and the surface becomes enriched with Au, as observed by cyclic voltammetry and elemental mapping. Such changes are mirrored by the evolution of electrocatalytic performances toward H₂O₂ production. Our experimental findings are finally summarized in a dissolution/structure/selectivity mechanism, providing a clear picture of the degradation of bimetallic catalyst used for H₂O₂ synthesis.

Publisher URL: http://dx.doi.org/10.1021/acscatal.7b01447

DOI: 10.1021/acscatal.7b01447