Catalytic reduction of CO₂ to CO via reverse water gas shift (RWGS) reaction provides a feasible approach to utilize CO₂, since CO can be further converted to various versatile products through the syngas routes. Ni-based catalysts are low cost and have a high activity for CO₂ reduction but are nonselective for RWGS due to competition from methanation. In this work, we demonstrated that surface modification of Ni by MoO_x can be tailored to tune the reactions of RWGS and methanation. The addition of MoO_x improves Ni dispersion through strong interactions whereas partially reduced MoO_x modifies the surface of Ni particles through both geometric coverage and electronic modification. No CO adsorption was observed at room temperature on the NiMo catalyst with a Mo/Ni ratio of 1, confirmed by density functional theory calculation. Tracking product evolution showed that CO₂ is first reduced to CO through RWGS on the Ni catalysts and methane is a product of CO hydrogenation. Apparent activation energy analysis indicates that the overall reaction is controlled by CO desorption. Addition of a small amount of Mo (Mo/Ni ratio of 0.1) shifts the reaction further to methanation selective with ∼100% CH₄ selectivity as MoO_x aids in the activation of both CO₂ and CO. In contrast, the addition of a large amount of Mo (Mo/Ni ratio of 1) shifts the reaction to RWGS selective with a CO selectivity > 94%. This is attributed to the enhanced CO desorption from the surface as a result of MoO_x modification.

通过反向水煤气变换 (RWGS) 反应将 CO ₂催化还原为 CO提供了一种利用 CO ₂的可行方法，因为 CO 可以通过合成气路线进一步转化为各种通用产品。镍基催化剂成本低，对 CO ₂还原具有高活性，但由于甲烷化的竞争，对 RWGS 没有选择性。在这项工作中，我们证明了 MoO _x对 Ni 的表面改性可以调整以调整 RWGS 和甲烷化的反应。MoO _x的添加通过强相互作用改善了 Ni 的分散性，而部分减少了 MoO _x通过几何覆盖和电子修饰来修饰 Ni 颗粒的表面。通过密度泛函理论计算证实，在室温下，在 Mo/Ni 比为 1 的 NiMo 催化剂上没有观察到 CO 吸附。跟踪产物演化表明，CO ₂首先通过镍催化剂上的 RWGS 还原为 CO，而甲烷是 CO 加氢的产物。表观活化能分析表明整个反应受 CO 解吸控制。添加少量 Mo（Mo/Ni 比为 0.1）将反应进一步转移到甲烷化选择性，CH ₄选择性约为 100%，因为 MoO _x有助于两种 CO ₂的活化和 CO。相比之下，添加大量 Mo（Mo/Ni 比为 1）将反应转变为 RWGS 选择性，CO 选择性 > 94%。这归因于 MoO _x改性导致从表面增强的 CO 解吸。