Dynamic Evolution of Palladium Single Atoms on Anatase Titania Support Determines the Reverse Water-Gas Shift...

Area of Science:

• Heterogeneous Catalysis
• Materials Science
• Surface Chemistry

Background:

• Single-atom catalysts (SACs) show promise but their dynamic evolution during reactions is poorly understood.
• Understanding dynamic behaviors is crucial for catalyst development and mechanistic insights.

Purpose of the Study:

• Investigate the evolution of active sites in Pd/TiO2-anatase SAC (Pd1/TiO2) during the reverse water-gas shift (rWGS) reaction.
• Elucidate how catalyst structure and activity are modulated by dynamic changes.

Main Methods:

• Combined kinetic studies, in situ characterization, and theoretical calculations.
• Investigated catalyst evolution under H2 reduction, oxidation, and CO treatment.
• Monitored Pd atom/cluster/particle formation and changes in coordination environment.

Main Results:

• H2 reduction at T ≥ 350 °C alters Pd coordination, creating highly active sites via a carboxyl pathway.
• Partial sintering of Pd1 to disordered ~1 nm clusters (Pd_x) occurs under H2 activation.
• Oxidation eliminates active sites but can redisperse Pd_x; CO treatment leads to deactivated ~5 nm Pd nanoparticles (Pd_NP).

Conclusions:

• The coordination environment and nuclearity of SACs evolve significantly during catalysis and pretreatments.
• H2 activation pathway dominates during rWGS, leading to increased activity and steady-state active sites.
• Insights into SAC dynamics and structure-function relationships are vital for catalyst design.