Tuning support morphology to control alloy over PtCo/γ-Al2O3 for the preferential oxidation of CO
The preferential oxidation of CO(CO-PROX)reaction is a cost-effective method for eliminating trace amounts of CO from the fuel H2.Pt-based catalysts have been extensively studied for CO-PROX,with their activity influenced by the morphology of the support.Hydrothermal synthesis was employed to produce different morphologies of γ-Al2O3:flower-like γ-Al2O3(f)exposing(110)crystal faces,sheet-like γ-Al2O3(s)revealing(100)crystal faces,and rod-like γ-Al2O3(r)displaying(111)crystal faces,followed by loading PtCo nanoparticles.The exposed crystal faces of the support impact the alloying degree of the PtCo nanoparticles,and an increase in the alloying degree correlates with enhanced catalyst reactivity.Pt3Co intermetallic compounds were identified on γ-Al2O3(f)exposing(110)crystal faces,and PtCo/γ-Al2O3(f)showed high catalytic activity in the CO-PROX reaction,achieving 100%CO conversion across a broad temperature range of 50-225℃.In contrast,only partial alloying of PtCo was observed on γ-Al2O3(s).Furthermore,no alloying between Pt and Co occurred in PtCo/γ-Al2O3(r),resulting in a reaction rate at 50℃ that was merely 11%of that of PtCo/γ-Al2O3(f).The formation of Pt3Co intermetallic compounds led to a more oxidized state of Pt,which significantly diminished the adsorption of CO on Pt and augmented the active oxygen species,thereby facilitating the selective oxidation of CO.
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