Abstract
Single-atom catalysts (SACs) have attracted considerable attention in the catalysis community. However, fabricating intrinsically stable SACs on traditional supports (N-doped carbon, metal oxides, etc.) remains a formidable challenge, especially under high-temperature conditions. Here, we report a novel entropy-driven strategy to stabilize Pd single-atom on the high-entropy fluorite oxides (CeZrHfTiLa)Ox (HEFO) as the support by a combination of mechanical milling with calcination at 900 °C. Characterization results reveal that single Pd atoms are incorporated into HEFO (Pd1@HEFO) sublattice by forming stable Pd–O–M bonds (M = Ce/Zr/La). Compared to the traditional support stabilized catalysts such as Pd@CeO2, Pd1@HEFO affords the improved reducibility of lattice oxygen and the existence of stable Pd–O–M species, thus exhibiting not only higher low-temperature CO oxidation activity but also outstanding resistance to thermal and hydrothermal degradation. This work therefore exemplifies the superiority of high-entropy materials for the preparation of SACs.
Highlights
Single-atom catalysts (SACs) have attracted considerable attention in the catalysis community
It should be noted that the molar ratios of Ce, Zr, Hf, Ti, and La are approximately 1:1:1:1:1 confirmed by both energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma (ICP) results listed in Supplementary Table 1
The high surface-area high-entropy fluorite oxides (CeZrHfTiLa)Ox (HEFO) is synthesized through the same steps without the addition of Pd precursor; Pd@CeO2 counterpart is prepared by the same method; the single-phase CeO2, TiO2, ZrO2, La2O3, and HfO2 are obtained from facile pyrolysis of their corresponding metal salts at 900 °C
Summary
Single-atom catalysts (SACs) have attracted considerable attention in the catalysis community. We report a novel entropy-driven strategy to stabilize Pd single-atom on the high-entropy fluorite oxides (CeZrHfTiLa)Ox (HEFO) as the support by a combination of mechanical milling with calcination at 900 °C. Compared to the traditional support stabilized catalysts such as Pd@CeO2, Pd1@HEFO affords the improved reducibility of lattice oxygen and the existence of stable Pd–O–M species, exhibiting higher low-temperature CO oxidation activity and outstanding resistance to thermal and hydrothermal degradation. New entropy-stabilized single-phase fluorite oxides (HEFO) Hf0.25Zr0.25Ce0.25Y0.25O2–δ11 and Ce0.2Zr0.2Hf0.2Sn0.2Ti0.2O212 were synthesized by using high-energy ball milling. Fabricating sintering-resistant SACs with intrinsically thermodynamic stability on high-entropy supports by using a solvent-free synthetic strategy is highly desirable. The catalytic activity of CO oxidation, as well as the resistance to thermal and hydrothermal degradation are compared for Pd1@HEFO and Pd@CeO2 catalysts to prove the advantages of HEFO as the catalyst carrier
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