Facet-engineering palladium nanocrystals for remarkable photocatalytic dechlorination of polychlorinated biphenyls

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Abstract

Rationally constructing functionalized cocatalysts for removing chemically inert polychlorinated biphenyls is significant and challenging.

Abstract

Rationally constructing functionalized cocatalysts for removing chemically inert polychlorinated biphenyls is significant and challenging. In this study, we have synthesized uniform Pd nanocrystals (Pd NCs) with cube (CUB) and octahedron (OCT) geometries, corresponding to the exposed (100) and (111) facets, and they were incorporated with ultrathin TiO ₂(B) nanosheets (TBs) for the photocatalytic dechlorination of polychlorinated biphenyls under visible light illumination ( λ ≥ 400 nm). Photocatalytic performance experiments revealed that CUB/TBs is more efficient with a 200% enhancement higher than OCT/TBs. Physicochemical characterizations reveal that the CUB possesses higher surface charge density than OCT, which promotes the activation of the C–Cl bond of polychlorinated biphenyls, leading to higher dechlorination performances of CUB/TBs than OCT/TBs. This study not only fundamentally elucidates the effect of facet-engineering palladium nanocrystals on the photocatalytic dechlorination of polychlorinated biphenyls, but also paves the way for rationally fabricating superior photocatalysts for other advanced applications.

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Photochemical route for synthesizing atomically dispersed palladium catalysts

P. Liu, Y. Zhao, R Qin … (2016)

Atomically dispersed noble metal catalysts often exhibit high catalytic performances, but the metal loading density must be kept low (usually below 0.5%) to avoid the formation of metal nanoparticles through sintering. We report a photochemical strategy to fabricate a stable atomically dispersed palladium-titanium oxide catalyst (Pd1/TiO2) on ethylene glycolate (EG)-stabilized ultrathin TiO2 nanosheets containing Pd up to 1.5%. The Pd1/TiO2 catalyst exhibited high catalytic activity in hydrogenation of C=C bonds, exceeding that of surface Pd atoms on commercial Pd catalysts by a factor of 9. No decay in the activity was observed for 20 cycles. More important, the Pd1/TiO2-EG system could activate H2 in a heterolytic pathway, leading to a catalytic enhancement in hydrogenation of aldehydes by a factor of more than 55.

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Tackling CO Poisoning with Single-Atom Alloy Catalysts.

Jilei Liu, Felicia Lucci, Ming Ming Yang … (2016)

Platinum catalysts are extensively used in the chemical industry and as electrocatalysts in fuel cells. Pt is notorious for its sensitivity to poisoning by strong CO adsorption. Here we demonstrate that the single-atom alloy (SAA) strategy applied to Pt reduces the binding strength of CO while maintaining catalytic performance. By using surface sensitive studies, we determined the binding strength of CO to different Pt ensembles, and this in turn guided the preparation of PtCu alloy nanoparticles (NPs). The atomic ratio Pt:Cu = 1:125 yielded a SAA which exhibited excellent CO tolerance in H2 activation, the key elementary step for hydrogenation and hydrogen electro-oxidation. As a probe reaction, the selective hydrogenation of acetylene to ethene was performed under flow conditions on the SAA NPs supported on alumina without activity loss in the presence of CO. The ability to maintain reactivity in the presence of CO is vital to other industrial reaction systems, such as hydrocarbon oxidation, electrochemical methanol oxidation, and hydrogen fuel cells.