Deoxygenation of IrO2(110) surface: Core-level spectroscopy and density functional theory calculation

作者：Chung Wen Hung; Wang Chia Ching; Tsai Dah Shyang^*; Jiang Jyh Chiang; Cheng Yu Chang; Fan Liang Jen; Yang Yaw Wen; Huang Ying Sheng

来源：Surface Science, 2010, 604(2): 118-124.

DOI：10.1016/j.susc.2009.10.027

• Iridium
• Catalysis
• Surface reaction
• Core-level spectroscopy
• Density functional theory calculations

Deoxygenation of the IrO2(1 1 0) surface is investigated at 403-493 K, using the core-level spectroscopy and density functional theory (DFT) calculation. The Ir-4f(7/2) signals of 1f-cus-Ir with and without on-top oxygen (O-top) emerge as surface features of the baked-out surface, whose positive and negative shifts in binding energy are in line with the DFT computation results. Progressively increasing the reduction temperature, the 1f-cus-Ir feature quickly disappears and the signal of 2f-cus-Ir emerges at 403 K. Meanwhile the feature of 1f-cus-Ir + O-top diminishes but persists when the It metal signal is evident. The intriguing coexistence of 1f-cus-Ir + O-top and Ir metal at 433-443 K is elucidated in the theoretical pathway study. DFT calculation reveals that O-2 desorption via pairing two neighboring O-top atoms is the rate-determining step of surface deoxygenation. Under the UHV conditions, O-top is replenished via migration of the surface oxygen species, including the threefold coordinated oxygen (O-3f) of a reduced surface. Hence the O-top atom is an active and long-lived surface species, which does not vanish until O-3f is consumed and surface It begins to cluster. Under the realistic pressure conditions, O-top can also be refreshed via the dissociative adsorption of gas-phase oxygen. In either pathway, O-top is a critical intermediary of IrO2(1 1 0) oxidation catalysis.

• 出版日期2010-1-15