TY - JOUR
T1 - In Situ PDF Study of the Nucleation and Growth of Intermetallic PtPb Nanocrystals
AU - Saha, Dipankar
AU - Bojesen, Espen D.
AU - Mamakhel, Mohammad Aref Hasen
AU - Bremholm, Martin
AU - Iversen, Bo B.
PY - 2017/7
Y1 - 2017/7
N2 - The mechanism of Pt and PtPb nanocrystal formation under supercritical ethanol conditions has been investigated by means of in situ X-ray total scattering and pair distribution function (PDF) analysis. The metal complex structures of two different platinum precursor solutions, chloroplatinic acid and Pt(acac)(2) (acac=acetylacetonate) provide atomic-scale detail about the nucleation mechanisms after initiation of the reaction with Pb(acac)(2) by heating. The stronger Pt-O chemical bonding in the Pt(acac)(2) precursor complex compared with the Pt-Cl bonding in the chloroplatinic acid precursor complex leads to a much slower reduction of the Pt center, and this allows more optimal co-reduction conditions providing a pathway for formation of phase-pure intermetallic PtPb product. The matching chemistry of the Pt(acac)(2) and Pb(acac)(2) precursors allow development of a facile continuous flow supercritical ethanol process for obtaining phase-pure hexagonal PtPb nanocrystals. The study thus highlights the importance of in situ studies in revealing atomic-scale information about nucleation mechanisms, which can be used in design of specific synthesis pathways, and the new continuous-flow process to obtain PtPb nanocrystals holds potential for large-scale production.
AB - The mechanism of Pt and PtPb nanocrystal formation under supercritical ethanol conditions has been investigated by means of in situ X-ray total scattering and pair distribution function (PDF) analysis. The metal complex structures of two different platinum precursor solutions, chloroplatinic acid and Pt(acac)(2) (acac=acetylacetonate) provide atomic-scale detail about the nucleation mechanisms after initiation of the reaction with Pb(acac)(2) by heating. The stronger Pt-O chemical bonding in the Pt(acac)(2) precursor complex compared with the Pt-Cl bonding in the chloroplatinic acid precursor complex leads to a much slower reduction of the Pt center, and this allows more optimal co-reduction conditions providing a pathway for formation of phase-pure intermetallic PtPb product. The matching chemistry of the Pt(acac)(2) and Pb(acac)(2) precursors allow development of a facile continuous flow supercritical ethanol process for obtaining phase-pure hexagonal PtPb nanocrystals. The study thus highlights the importance of in situ studies in revealing atomic-scale information about nucleation mechanisms, which can be used in design of specific synthesis pathways, and the new continuous-flow process to obtain PtPb nanocrystals holds potential for large-scale production.
KW - continuous flow synthesis
KW - intermetallic
KW - nanoparticles
KW - pair distribution function
KW - supercritical ethanol
KW - X-RAY-SCATTERING
KW - PAIR DISTRIBUTION-FUNCTIONS
KW - METAL-OXIDE NANOPARTICLES
KW - CONTINUOUS-FLOW SYNTHESIS
KW - ELECTROCATALYTIC ACTIVITY
KW - SUPERCRITICAL FLUIDS
KW - HYDROTHERMAL SYNTHESIS
KW - FUEL-CELLS
KW - POWDER DIFFRACTION
KW - SYNCHROTRON-RADIATION
U2 - 10.1002/cnma.201700069
DO - 10.1002/cnma.201700069
M3 - Journal article
SN - 2199-692X
VL - 3
SP - 472
EP - 478
JO - ChemNanoMat
JF - ChemNanoMat
IS - 7
ER -