Theoretical and experimental investigations on single-atom catalysis: Pt₁/FeO_x for water-gas shift reaction

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.