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Methane (CH4) oxidation is an important reaction to reduce the greenhouse effect caused by incomplete combustion of CH4. Here, we explored the mechanism of CH4 oxidation catalyzed by CeO2 and Ni-doped CeO2, focusing on the redox properties of these catalyst surfaces, using density functional theory (DFT). We found that the barriers for CH4* activation and H2O* formation are correlated with the surface redox capacity, which is enhanced by Ni doping. Furthermore, the complete reaction mechanism is explored by DFT calculations and microkinetic simulations on bare and Ni-doped CeO2 surfaces. Our calculations suggest that the doping of Ni leads to a much higher overall reactivity, due to a balance between the CH4* activation and H2O* formation steps. These results provide insights into the CH4 oxidation mechanism and the intrinsic relationship between redox properties and the activity of CeO2 surfaces. 

Frustrated Lewis pair (FLP) catalysts have attracted much recent interest because of their exceptional ability to activate small molecules in homogeneous catalysis. In the past ten years, this unique catalysis concept has been extended to heterogeneous catalysis, with much success. Herein, we review the recent theoretical advances in understanding FLP-based heterogeneous catalysis in several applications, including metal oxides, functionalized surfaces, and two-dimensional materials. A better understanding of the details of the catalytic mechanism can help in the experimental design of novel heterogeneous FLP catalysts. 

Ceria (CeO 2 ) has recently been found to catalyze the selective hydrogenation of alkynes, which has stimulated much discussion on the catalytic mechanism on various facets of reducible oxides. In this work, H 2 dissociation and acetylene hydrogenation on bare and Ni doped CeO 2 (110) surfaces are investigated using density functional theory (DFT). Similar to that on the CeO 2 (111) surface, our results suggest that catalysis is facilitated by frustrated Lewis pairs (FLPs) formed by oxygen vacancies (O v s) on the oxide surfaces. On bare CeO 2 (110) with a single O v (CeO 2 (110)–O v ), two surface Ce cations with one non-adjacent O anion are shown to form (Ce 3+ –Ce 4+ )/O quasi-FLPs, while for the Ni doped CeO 2 (110) surface with one (Ni–CeO 2 (110)–O v ) or two (Ni–CeO 2 (110)–2O v ) O v s, one Ce and a non-adjacent O counterions are found to form a mono-Ce/O FLP. DFT calculations indicate that Ce/O FLPs facilitate the H 2 dissociation via a heterolytic mechanism, while the resulting surface O–H and Ce–H species catalyze the subsequent acetylene hydrogenation. With CeO 2 (110)–O v and Ni–CeO 2 (110)–2O v , our DFT calculations suggest that the first hydrogenation step is the rate-determining step with a barrier of 0.43 and 0.40 eV, respectively. For Ni–CeO 2 (110)–O v , the reaction is shown to be controlled by the H 2 dissociation with a barrier of 0.41 eV. These barriers are significantly lower than that (about 0.7 eV) on CeO 2 (111), explaining the experimentally observed higher catalytic efficiency of the (110) facet of ceria. The change of the rate-determining step is attributed to the different electronic properties of Ce in the Ce/O FLPs – the Ce f states closer to the Fermi level not only facilitate the heterolytic dissociation of H 2 but also lead to a higher barrier of acetylene hydrogenation. 

In this work, we study the water−gas shift (WGS) reaction catalyzed by α- MoC(100) supported typical platinum group metal (PGM) single atoms (Rh1, Pd1, and Pt1) and Au1 via density functional theory calculations. The adsorption energies of key reaction intermediates and the kinetic barriers of the proposed rate-determining step in the WGS were systematically investigated. It is found that Rh1, Pd1, and Pt1 can serve as single-atom promoters (SAPs) to improve the WGS performance of surface Mo atoms on α-MoC(100). The enhanced activity originates from the fact that SAP modifies the electronic structure of Mo active sites. Comparatively, the Au1 species not only acts as an SAP but also directly participates in the catalysis as a single-atom player. The additional experiments with singleatomcatalyst performance and kinetic studies confirm the theoretical calculation conclusions. This study can provide a basis to further develop efficient WGS catalysts by tuning the activity of the substrate with intercalation of SAPs.