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One-Pot Synthesis of Pd@PtnL Core-Shell Icosahedral Nanocrystals in High Throughput through a Quantitative Analysis of the Reduction Kinetics |
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| Authors: | Chi-Ta Lee Dr Helan Wang Ming Zhao Dr Tung-Han Yang Dr Madeline Vara Prof Dr Younan Xia |
| Institution: | 1. School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332 USA
These authors contributed equally to this work.;2. The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, 30332 USA These authors contributed equally to this work.;3. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, 30332 USA;4. The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, 30332 USA;5. School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332 USA |
| Abstract: | The rational design and implementation of a one-pot method is reported for the facile synthesis of Pd@PtnL (nL denotes the number of Pt atomic layers) core-shell icosahedral nanocrystals in a single step. The success of this method relies on the use of Na2PdCl4 and Pt(acac)2 as the precursors to Pd and Pt atoms, respectively. Our quantitative analysis of the reduction kinetics indicates that the PdII and PtII precursors are sequentially reduced with a major gap between the two events. Specifically, the PdII precursor is reduced first, leading to the formation of Pd-based icosahedral seeds with a multiply-twinned structure. In contrast, the PtII precursor prefers to take a surface reduction pathway on the just-formed icosahedral seeds. As such, the otherwise extremely slow reduction of the PtII precursor can be dramatically accelerated through an autocatalytic process for the deposition of Pt atoms as a conformal shell on each Pd icosahedral core. Compared to the conventional approach of seed-mediated growth, the throughput for the one-pot synthesis of Pd@PtnL core-shell nanocrystals can be increased by more than 30-fold. When used as catalysts, the Pd@Pt4.5L core-shell icosahedral nanocrystals show specific and mass activities of 0.83 mA cm−2 and 0.39 A mgPt−1, respectively, at 0.9 V toward oxygen reduction. The Pt-based nanocages derived from the core-shell nanocrystals also show enhanced specific (1.45 mA cm−2) and mass activities (0.75 A mgPt−1) at 0.9 V, which are 3.8 and 3.3 times greater than those of the commercial Pt/C, respectively. |
| Keywords: | core–shell kinetic study one-pot oxygen reduction reaction platinum |