隨著全球暖化日益加劇，透過逆水煤氣變換反應（reverse water-gas shift， RWGS）將溫室氣體CO2轉化為高附加價值的CO，不僅能為緩解氣候變遷提供具備潛力的途徑，同時亦能兼顧產業經濟效益。過往文獻指出，貴金屬（如Pt、Pd）在RWGS反應中具有促進氫氣解離的能力，而MoO3因其表面有利於形成可逆氧化還原循環（Reverse Mars-van Krevelen 機制），使其成為能夠有效活化CO2轉化為CO的可還原性載體。然而，過去相關研究在貴金屬負載之可還原金屬氧化物的觸媒系統中，對於貴金屬如何影響金屬氧化物載體在反應過程中的結構演變仍缺乏系統性的探討。 本研究透過不同的合成方法（包含水熱合成法與傳統含浸法）製備 MoO3、Pd/MoOx-HT及 MoOx/PdO/SiO2 催化劑，藉此調控Pd與鉬氧化物形成不同接觸程度之界面。此外，本研究亦利用原位漫反射傅立葉變換紅外光譜（In-situ diffuse reflectance infrared fourier transform spectroscopy， In-situ DRIFTS）技術，深入探討不同Pd-MoOx之接觸程度對於鉬氧化物在反應過程中之動態結構變化及催化機制的影響。結果顯示，MoO3載體系統在逆水煤氣變換反應中主要遵循氧化還原的催化機制，且鈀的負載會促使鉬氧化物表面能夠更有效率地產生缺陷位點，進而提升CO2的轉化效率；其中，此效應又以「完全接觸界面」結構更為顯著，而「部分接觸界面」結構則因氫溢流效應受阻，其鉬氧化物表面的還原行為受到限制。X光光電子能譜（X-ray photoelectron spectroscopy， XPS）結果顯示，Mo 3d電子的束縛能在RWGS 反應後向低值方向偏移，此現象與透過X-射線繞射（X-ray diffraction， XRD） 觀測到的鉬氧化物還原趨勢相互吻合。本研究亦進行反應級數之測定，根據CO2負一級之結果推論，隨著測試過程CO2濃度逐漸下調，樣品表面更具催化活性的氧缺陷鉬物種隨反應流程推進而持續遞增，因而呈現更好的催化表現。本研究不僅深入探討鉬氧化物在RWGS反應過程中的結構動態變化，亦為釐清Pd在Pd-Mo雙金屬催化劑於 RWGS 反應過程中所扮演的角色，提供更加深刻的理解。;With the exacerbation of global warming， converting the greenhouse gas CO2 into high-value CO via the reverse water-gas shift (RWGS) reaction offers a promising pathway to mitigate climate change while balancing industrial economic benefits. Previous literature indicates that noble metals (e.g.， Pt， Pd) possess the capability to promote hydrogen dissociation， whereas MoO3 serves as an effective reducible support for CO2 activation and conversion to CO due to its propensity for forming a reversible redox cycle via the reverse Mars–van Krevelen mechanism. However， systematic investigations into how noble metals influence the structural evolution of reducible metal oxide supports during the reaction within such catalyst systems remain limited. In this study， MoO3， Pd/MoOx-HT， and MoOx/PdO/SiO2 catalysts were synthesized using various methods， including hydrothermal synthesis and conventional impregnation， to fine-tune the degree of interfacial contact between Pd and molybdenum oxides. Furthermore， in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) was also utilized to gain deep insights into the influence of different Pd-MoOx contact degrees on the dynamic structural evolution and catalytic mechanisms of molybdenum oxides during the reaction. The results demonstrate that the MoO3-supported system operates primarily via a redox catalytic mechanism in the reverse water-gas shift (RWGS) reaction. Furthermore， Pd incorporation facilitates the more efficient generation of surface defect sites on molybdenum oxides， thereby boosting CO2 conversion efficiency. This promotional effect is most pronounced in the "fully-contacted interface" structure; in contrast， in the "partially-contacted interface" structure， the reduction behavior of molybdenum oxides is constrained due to hindered hydrogen spillover. X-ray photoelectron spectroscopy (XPS) analysis showed that the binding energy of Mo 3d electrons shifted toward lower values after the RWGS reaction， a phenomenon highly consistent with the reduction trend of molybdenum oxides observed via X-ray diffraction (XRD). Reaction order measurements were also conducted; based on the negative first-order dependence on CO2， it is inferred that as the CO2 concentration was progressively decreased during the testing sequence， the highly active oxygen-deficient molybdenum species on the sample surface continuously increased over time， thereby leading to enhanced catalytic performance. Overall， this study not only provides insights into the dynamic structural changes of molybdenum oxides during the RWGS reaction but also offers a profound understanding of the role played by Pd in Pd-Mo bimetallic catalysts.
