Dual-edged sword effects of sulfation/hydration on Ce-doped TiO2(001) single-atom catalyst for NH3-SCR reaction: A first-principles study.

[Display omitted] • Ce-doped TiO 2 (0 0 1) single-atom (SA) catalyst exhibit superior SO 2 /H 2 O-resistance. • CT(0 0 1)-SA protect Ce site from sulfation/hydration with TiO 2 (0 0 1) as trapping site. • Electron capture behavior of SO 2 /H 2 O cause an electron-deficient state of CT(0 0 1)-SA. • Electron-deficiency promote NH 3 adsorption and suppress secondary sulfation/hydration. • Sulfation/hydration exhibite a "dual-edged sword" effect for NH 3 -SCR on CT(0 0 1)-SA. SO 2 /H 2 O-resistance remains challenges for selective catalytic reduction with NH 3 (NH 3 -SCR). The detailed promotion and/or inhibition effects of sulfation/hydration on cerium-titanium (CT) catalysts for NH 3 -SCR are still controversial. Herein, a series of adsorption characteristics, bonding strengths, electronic effects, and reaction pathways were performed by first-principles density functional theory calculations to explore the structure-performance/resistance of CT catalysts and unravel the effects of sulfation/hydration for NH 3 -SCR. We constructed six CT catalyst structures based on three TiO 2 facets [(0 0 1)/(1 0 1)/(1 0 0)] and two surface configurations [single-atom (SA)/interface (IF)]. CT(0 0 1)-SA could protect the active Ce site from sulfation/hydration with TiO 2 (0 0 1) as SO 2 /H 2 O-trapping site, which was the optimal SO 2 /H 2 O-resistant structure among six CT catalyst structures. An electron-deficient state of CT(0 0 1)-SA was caused by sulfation/hydration through electron capture behavior. From the perspective of reactants adsorption, this electron-deficient state not only promoted the NH 3 /NO adsorption but also suppressed the secondary sulfation/hydration. As for NH 3 -SCR pathways, hydration promoted NH 3 dissociation, N-N coupling, and N-O breaking, but inhibited the H1 transfer (rate-determining step). Sulfation impaired the redox ability of Ce site, promoted H1 transfer and N-O breaking, but inhibited the NH 3 dissociation, N-N coupling, and H2 transfer (rate-determining step). Hence, sulfation/hydration exhibited "dual-edged sword" effects for NH 3 -SCR on CT(0 0 1)-SA via electronic effects. [ABSTRACT FROM AUTHOR]