Role of oxide support in stabilizing Ag single atom catalyst and subsequent NH₃ adsorption

Single atom catalyst (SAC) supported on metal oxides is a promising candidate for various reactions as it may possess high temperature stability and potentially high selectivity. We present results of density functional theory-based calculations, including the Hubbard parameter U for Ce and Zr, that trace the catalytic activity of the Ag SAC supported on ceria and zirconia ease of O vacancy formation on the support. We find the formation energy of a single O vacancy near the Ag atom on CeO₂ (ııo) and ZrO₂ (īıı) <!--[if gte msEquation 12]> m:val="̅"/> style='mso-bidi-font-style:normal'>1 style='mso-bidi-font-style:normal'>11 to be -0.54 and 0.61 eV, respectively, while that for O bivacancy are -0.17 and 3.64 eV, respectively. On CeO₂ (ııo) supported Ag SAC with no O vacancy, NH₃ prefers to bind on the Ag atom with binding energy of -1.26 eV which decreases to -1.08 eV in the presence of the O vacancy. With O bivacancy NH₃ preferably adsorbs on a Ce atom with adsorption energy of -0.89 eV. We compare the trends in the energetics of NH₃ on Ag SAC supported on CeO₂ (ııo) with those on ZrO₂ (īıı) and provide a rationale for the observed significantly enhanced catalytic performance in NH₃ oxidation on Ag SAC supported on ceria as compared to that supported on zirconia [1].

[1] K. Ye, S. Xie, and F. Liu, private communication.