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Download fileCompensation Effect Exhibited by Gold Bimetallic Nanoparticles during CO Oxidation
journal contribution
posted on 21.09.2021, 07:44 authored by Joe Brindle, Michael M. NigraWhile CO oxidation
catalyzed by gold nanoparticles has been practiced
academically for several decades, there are still important discoveries
to be made. One area of current interest is to pair Au with another
alloying metal and observe the catalytic consequences of the presence
of the other metal. In this work, TiO2-supported bimetallic
Au nanoparticles are alloyed with Cu, Co, Ni, Pd, and Ru and used
as catalysts for CO oxidation. Two synthetic methods for the alloys
are presented: a strong electrostatic adsorption (SEA) method and
a sterically demanding ligand synthesis (SDLS) method which uses triphenylphosphine
(TPP) as the ligand. The catalytic performance of the materials synthesized
with the SEA and SDLS methods is compared in CO oxidation. The results
indicate that the materials tested present an enthalpy–entropy
compensation effect. Interestingly, both the enthalpy of activation,
ΔH‡, and the entropy of activation,
ΔS‡, generally decrease with
particle size. AuCo and AuRu materials exhibit a decrease in the overall
activity as compared to Au and the other Au alloys when synthesized
via SEA. Au face-centered-cubic alloys AuCu, AuNi, and AuPd prepared
via SEA show an improvement in activity compared to monometallic Au
in our reaction conditions. In situ diffuse reflectance
infrared Fourier transform spectroscopy presents two distinct regions
for Au bimetallics where AuCo and AuRu show peak positions in the
region of 2070–2050 cm–1, indicating a weaker
interaction for AuCo and AuRu with CO when compared to that of the
other alloys. For the SDLS method samples, the hypothesis is that
TPP would enhance the CO oxidation rate by enhancing the charge transfer
to the metallic surface. The results indicate that SDLS samples have
lower CO oxidation rates and if any charge transfer occurs, it is
masked by the lateral interactions of the CO π bonds and the
phenyl groups of TPP.
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strong electrostatic adsorptionstill important discoveriescompensation effect exhibitedmaterials tested presenttwo synthetic methodsco π bondsco oxidation rateco oxidation catalyzedtpp would enhancegold bimetallic nanoparticlescubic alloys aucucharge transfer occursanother alloying metalauru materials exhibitsynthesized via seasdls method samplesmaterials synthesizedco oxidationgold nanoparticlescharge transfersdls samplessdls methodsweaker interactionuses triphenylphosphineseveral decadesresults indicatereaction conditionspracticed academicallyphenyl groupsparticle sizeoverall activityone areametallic surfacelateral interactionscurrent interestcatalytic performancecatalytic consequences