Al-Pt compounds catalyzing the oxygen evolution reaction.

Al-Pt compounds have been systematically studied as electrocatalysts for the oxygen evolution reaction (OER). Considering the harsh oxidative conditions of the OER, all Al-Pt compounds undergo modifications during electrochemical experiments. However, the degree of changes strongly depends on the composition and crystal structure of a compound. In contrast to Al-rich compounds (Al 4 Pt and Al 21 Pt 8 ), which reveal strong leaching of aluminum, changes in other compounds (Al 2 Pt, Al 3 Pt 2 , rt-AlPt, Al 3 Pt 5 , and rt-AlPt 3 ) take place only on the surface or in the near-surface region. Furthermore, surface modification leads to a change in the electronic structure of Pt, giving rise to the in situ formation of catalytically more active surfaces, which are composed of intermetallic compounds, Pt-rich Al x Pt 1- x phases and Pt oxides. Forming a compromise between sufficient OER activity and stability, Al 2 Pt and Al 3 Pt 2 can be considered as precursors for OER electrocatalysts.