201. Role of surface steps in activation of surface oxygen sites on Ir nanocrystals for oxygen evolution reaction in acidic media.
- Author
-
Kim, Myeongjin, Park, Jinho, Wang, Maoyu, Wang, Qingxiao, Kim, Moon J., Kim, Jin Young, Cho, Hyun-Seok, Kim, Chang-Hee, Feng, Zhenxing, Kim, Byung-Hyun, and Lee, Seung Woo
- Subjects
- *
OXYGEN evolution reactions , *NANOCRYSTALS , *CONCAVE surfaces , *SURFACE reconstruction , *DENSITY functional theory , *X-ray absorption , *ELECTROCATALYSTS - Abstract
Ir and its oxide are the only available oxygen evolution reaction (OER) electrocatalysts with reasonably high activity and stability for commercial proton-exchange membrane electrolyzers. However, the establishment of structure–performance relationships for the design of better Ir-based electrocatalysts is hindered by their uncontrolled surface reconstruction during OER in acidic media. Herein, we monitor the structural evolution of two model Ir nanocrystals (one with a flat surface enclosed by (100) facets and the other with a concave surface containing numerous high-index planes) under acidic OER conditions. Operando X-ray absorption spectroscopy measurements reveal that the promotion of surface IrO x formation during the OER by the concave Ir surface with high-index planes results in a gradual OER activity increase, while a decrease in activity and limited oxide formation are observed for the flat Ir surface. After the activation process, the Ir concave surface exhibits ~ 10 times higher activity than the flat surface. Density functional theory computations reveal that Ir high-index surfaces are thermodynamically preferred for the adsorption of oxygen atoms and the formation of surface oxides under OER conditions. Thus, our work establishes a structure–performance relationship for Ir nanocrystals under operating conditions, providing new principles for the design of nanoscale OER electrocatalysts. Surface structure–controlled model Ir nanocrystals with flat and concave surfaces were designed as electrocatalysts for the oxygen evolution reaction under acidic conditions. The Ir concave surface containing high-index planes exhibited progressive activation during the oxygen evolution reaction due to the facile formation of active IrO x , while the flat surface showed a gradual decrease in activity. [Display omitted] • Surface structure–controlled model Ir nanocrystals with flat and concave surfaces. • The structural evolution of Ir catalysts under acidic oxygen evolution reaction. • The activation process of Ir concave surface containing high-index planes under OER. • The deactivation process of Ir flat surface during acidic OER. • The important role of high-index planes for promoting OER activity in acidic media. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF