氧化釕與氧化銥(110)晶面之脫氧行為的研究可讓我們瞭解還原路徑與可能的反應位置。本研究利用拉曼光譜、X射線光電子能譜、掃描式穿隧顯微鏡、掃描式電子顯微鏡與X射線繞射分析氧化釕與氧化銥(110)之晶面。在過去的研究中，我們發現氧化釕與氧化銥奈米級的觸媒經過還原後可看到顯著提升的觸媒活性，此一現象驅使我進一步研究氧化釕與氧化銥(110)晶面的脫氧行為。
氧化釕與氧化銥屬於導電性的金屬氧化物。其晶體傾向於沿著c-軸生長並展現出(110)優選晶面。氧化釕(110)表面經過882 K還原後，可在其表面上發現許多沿著[001]方向延伸的裂縫及氧化態與金屬共存的表面。拉曼圖譜中新增的190 cm-1特徵峰可推論為金屬釕的貢獻，並隨著還原程度的增加而觀察到氧化釕Eg, A1g, B2g模式的強度降低。利用spatial correlation model擬合Eg特徵峰可估算表面上剩餘的氧化釕晶體大小。另外，583 K還原的XPS結果亦發現非均勻還原的現象。
於403 ~ 493 K還原後的氧化銥(110)晶面利用了同步輻射光源進行脫氧行為的核層光電子能譜與全電子密度泛函數理論計算的分析。較容易還原的氧化銥晶體在383 K還原後，核層光電子能譜可發現二種表層訊號：1f-cus-Ir（單重次未飽和配位的銥原子）與被Otop覆蓋的前述銥原子。逐步增加還原溫度可發現1f-cus-Ir訊號迅速消失；同時間1f-cus-Ir + Otop complex訊號減弱了卻持續出現，直至表面完全還原成金屬狀態，此一現象可利用DFT計算結果加以解釋。經過DFT計算，吾可發現相鄰成對的Otop原子結合脫附主導了表面的脫氧行為。在超高真空環境中Otop原子可藉由Obr原子與O3f原子的移動補充。因此，在表面完全還原成金屬狀態前，Otop原子變成了一種具有活性且持續存在於表面的氧原子。而在實際觸媒應用的環境中，Otop原子可藉由分解氣相中吸附的氧分子補充。由此可知在二種環境中，表面的Otop原子於觸媒中扮演著重要的角色。

Deoxygenation of the RuO2 and IrO2 (110) surfaces has been investigated to understand their reduction pathways and the probable active sites of partially reduced surface. In the present study, snapshots of the RuO2 and IrO2 surfaces are analyzed during thermal reduction, using microRaman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD). Motivation of the current research arises from the recent experimental results, gathered by our research group, which pointed out a dramatic enhancement in catalytic activity after reduction of RuO2 and IrO2 nanophase materials.
RuO2 and IrO2 of rutile structure belong to the oxide family of metallic conductivity, well reputed for their electrocatalytic applications. Growth of RuO2 and IrO2 crystals in its c-axis can be employed to develop one-dimensional structures with preferential (110) surface. The study on RuO2 (110) reduced surface reveals fissures elongated in the [001] direction, and coexistence of the oxide and the metallic phase on the partially reduced surface. A new Raman feature at 190 cm-1 has been observed as the Ru metal phase emerges, accompanying with the degradation of Eg, A1g, B2g modes for RuO2 when the single crystal was heated at 882 K. The grain size of residual RuO2 can be correlated from the broadening and shifting of Eg mode, using spatial correlation model. Analysis of Ru-3d and O-1s signals generated with an in-house XPS instrument also indicate the RuO2 (110) decomposes inhomogeneously at 583 K.
Using a more intense X-ray synchrotron radiation source, deoxygenation of IrO2 (110) was analyzed between 403 and 493 K with the core-level spectroscopy (CLS). The assignment of surface features is assisted with the all-electron density functional calculations (DFT). Since iridium is a more noble metal, the IrO2 (110), baked out at 383 K, exhibits two surface features of 1f-cus-Ir (one-fold coordinated unsaturated Ir atom) with and without on-top oxygen (Otop), implying the surface is somewhat oxygen rich. Progressively increasing the reduction temperature, the 1f-cus-Ir feature quickly disappears and the signal of 2f-cus-Ir (two-fold coordinated unsaturated Ir atom) emerges at 403 K. Meanwhile the feature of 1f-cus-Ir + Otop diminishes but persists when the Ir metal signal is evident. The coexistence of 1f-cus-Ir + Otop and Ir metal at 433 – 443 K is explained in the theoretical pathway study. DFT calculation reveals that O2 desorption via pairing two neighboring Otop atoms is the rate-determining step of surface deoxygenation. Under the ultra high vacuum (UHV) conditions, Otop is replenished via migration of the surface oxygen species, including the threefold coordinated oxygen (O3f) of a reduced surface. Hence the Otop atom is an active and long-lived surface species, which does not vanish until O3f is consumed and surface Ir atoms begin to cluster. Under the realistic pressure conditions, Otop can also be refreshed via the dissociative adsorption of gas-phase oxygen. In either pathway, Otop is a critical intermediary of IrO2 (110) for its oxidation catalysis.

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