Oxide-supported metal single-atom catalysts have exhibited excellent catalytic performance for water gas shift (WGS) reaction.  Here, we report the single-atom catalyst (SAC) Pt₁/FeO_x exhibits excellent medium temperature catalytic performance for WGS reactions by the density functional theory (DFT) calculations and experimental results. The calculations indicate that H₂O molecules are easily dissociated at oxygen vacancies, and the formed OH* and O* are adsorbed on Pt₁ single atoms and the adjacent O atoms, respectively. After studying four possible reaction mechanisms, the optimal WGS reaction pathway is proceeded along the carboxyl mechanism (Pathway III), in which the formation of *COOH intermediates can promote the stability of Pt₁/FeO_x SAC and the occurrence of WGS reaction more easily. The energy barrier of the rate-determining step during the entire reaction cycle is only 1.16 eV, showing the high activity for the medium temperature WGS reaction on Pt₁/FeO_x SAC, which was verified by experimental results. Moreover, the calculated turn-over frequencies (TOF) of CO₂ and H₂ formation on Pt₁/FeO_x at 610 K (337 ℃) can reach up to 1.14´10^-3 s⁻¹ site⁻¹ through carboxyl mechanism. In this work, we further expand the application potential of Pt₁/FeO_x SAC in water gas shift (WGS) reaction.

Electrochemical conversion of CO₂ into valuable hydrocarbon fuel is one of the key steps in solving carbon emission and energy issue. Herein, we report a non-noble metal catalyst, nickel single-atom catalyst (SAC) of Ni₁/UiO-66-NH₂, with high stability and selectivity for electrochemical reduction of CO₂ to CH₄. Based on ab initio molecular dynamics (AIMD) simulations, the CO₂ molecule is at first reduced into CO₂⁻ when stably adsorbed on a Ni single atom with the bidentate coordination mode. To evaluate its activity and selectivity for electrocatalytic reduction of CO₂ to different products (HCOOH, CO, CH₃OH, and CH₄) on Ni₁/UiO-66-NH₂, we have used density functional theory (DFT) to study different reaction pathways. The results show that CH₄ is generated preferentially on Ni₁/UiO-66-NH₂ and the calculated limiting potential is as low as −0.24 V. Moreover, the competitive hydrogen evolution reaction is unfavorable at the activation site of Ni₁/UiO-66-NH₂ owing to the higher limiting potential of −0.56 V. Furthermore, the change of Ni single atom valence state plays an important role in promoting CO₂ reduction to CH₄. This work provides a theoretical foundation for further experimental studies and practical applications of metal–organic framework (UiO-66)-based SAC electrocatalysts with high activity and selectivity for the CO₂ reduction reaction.