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Molecular and Dissociative Adsorption of Oxygen on Au-Pd Bimetallic Clusters: Role of Composition and Spin State of the Cluster.

ABSTRACT: Utilization of molecular oxygen as an oxidizing agent in industrially important reactions is the ultimate goal to design environmentally benign processes under ambient conditions. However, the high thermal stability and a large O-O dissociation barrier in O₂ molecule pose a great challenge toward its successful application in the oxidative chemistry. To achieve this goal, different catalysts based on monometallic and bimetallic clusters have been developed over the years to promote binding and dissociation of molecular oxygen. The successful design of efficient metal cluster catalysis needs an in-depth knowledge of synergistic effects between different metal atoms and intrinsic catalytic mechanisms for O₂ adsorption and dissociation. Here, we present a systematic theoretical investigation of reaction pathways for O₂ adsorption and dissociation on Au₈, Pd₈, and Au_8-n Pd _n (n = 1-7) nanoclusters in different spin states. The density functional calculations point out that the O₂ dissociation barriers can be significantly reduced with the help of certain bimetallic clusters along specific spin channels. Our results particularly indicate that Au₅Pd₃ and Au₁Pd₇ show very large O₂ binding energies of 1.76 and 1.69 eV, respectively. The enhanced O₂ binding subsequently leads to low activation barriers of 0.98 and 1.19 eV along the doublet and quartet spin channels, respectively, without the involvement of any spin flip-over for O₂ dissociation. Furthermore, the computed O₂ dissociation barriers are significantly low as compared to the already reported barriers (1.95-3.65 eV) on monometallic and bimetallic Au-Ag clusters. The results provide key mechanistic insights into the interaction and dissociation of molecular oxygen with Au-Pd clusters, which can prove informative for the design of efficient catalysts for oxidative chemistry involving molecular oxygen as a reactant.

SUBMITTER: Dar MA

PROVIDER: S-EPMC6682065 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Molecular and Dissociative Adsorption of Oxygen on Au-Pd Bimetallic Clusters: Role of Composition and Spin State of the Cluster.

Dar Manzoor Ahmad MA Krishnamurty Sailaja S

ACS omega 20190725 7

Utilization of molecular oxygen as an oxidizing agent in industrially important reactions is the ultimate goal to design environmentally benign processes under ambient conditions. However, the high thermal stability and a large O-O dissociation barrier in O<sub>2</sub> molecule pose a great challenge toward its successful application in the oxidative chemistry. To achieve this goal, different catalysts based on monometallic and bimetallic clusters have been developed over the years to promote bi ...[more]

PMID: 31460390

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Project description:DNA-mediated synthesis of nanoparticles with different morphologies has proven to be a powerful method to synthesize and access many exclusive shapes and surface properties. While previous studies employ seeds that contain relatively low-energy facets, such as a simple cubic palladium seed in the synthesis of Pd-Au bimetallic nanoparticles, few studies have investigated whether DNA molecules can still exert their influence when the synthesis uses a seed that contains high-energy facets. Seeds that are enclosed by such high-energy facets or sites are known to act as easy nucleation sites in nanoparticles growth and could potentially suppress the effect of DNA. To answer this question, we herein report DNA-encoded control of morphological evolution of bimetallic Pd@Au core-shell nanoparticles from a concave palladium nanocube seed that contains high indexed facets. Based on detailed spectroscopic and SEM studies of time-dependent growth of the bimetallic nanoparticles, we found that each of 10-mer DNA molecules (T10, G10, C10 and A10) has a unique way of interacting with both the seed's surface and the precursor. Among them, the most important factor is the binding affinity of the nucleobase to the Pd surface, with the A10 possessing the highest binding affinity and thus capable of stabilizing the seed's high energy surfaces. Furthermore, for bases with lower binding affinity (T10, G10 and C10) than A10, the growth is completely dictated by the seed's surface energy initially, but the later growth can still be influenced by the different DNA sequences, resulting in four unique morphologically different Pd@Au bimetallic nanoparticles. The effect of these DNA molecules with medium binding affinity can only be observed when there is more deposition of Au. Based on the above results, a scheme for the DNA controlled growth is proposed. Together these results have provided insights into factors governing DNA-mediated growth of core-shell structures using seeds with high-energy sites, and the insights can readily be applied to other bimetallic systems that adopt seed-mediated synthesis.

Dataset Information

Molecular and Dissociative Adsorption of Oxygen on Au-Pd Bimetallic Clusters: Role of Composition and Spin State of the Cluster.

Publications

Molecular and Dissociative Adsorption of Oxygen on Au-Pd Bimetallic Clusters: Role of Composition and Spin State of the Cluster.

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