Design and assembly of ternary Pt/Re/SnO2 NPs by controlling the zeta potential of individual Pt, Re, and SnO2 NPs
J Nanopart Res
Design and assembly of ternary Pt/Re/SnO2 NPs by controlling the zeta potential of individual Pt, Re, and SnO2 NPs
Elżbieta Drzymała 0 1
Grzegorz Gruzeł 0 1
Anna Pajor-Świerzy 0 1
Joanna Depciuch 0 1
Robert Socha 0 1
Andrzej Kowal 0 1
Piotr Warszyński 0 1
Magdalena Parlinska-Wojtan 0 1
0 A. Pajor-Świerzy
1 E. Drzymała (
In this study Pt, Re, and SnO2 nanoparticles (NPs) were combined in a controlled manner into binary and ternary combinations for a possible application for ethanol oxidation. For this purpose, zeta potentials as a function of the pH of the individual NPs solutions were measured. In order to successfully combine the NPs into Pt/SnO2 and Re/SnO2 NPs, the solutions were mixed together at a pH guaranteeing opposite zeta potentials of the metal and oxide NPs. The individually synthesized NPs and their binary/ ternary combinations were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) analysis. FTIR and XPS spectroscopy showed that the individually synthesized Pt and Re NPs are metallic and the Sn component was oxidized to SnO2. STEM showed that all NPs are well crystallized and the sizes of the Pt, Re, and SnO2 NPs were 2.2, 1.0, and 3.4 nm, respectively. Moreover, EDS analysis confirmed the successful formation of binary Pt/ SnO2 and Re/SnO2 NP, as well as ternary Pt/Re/ SnO2 NP combinations. This study shows that by controlling the zeta potential of individual metal and oxide NPs, it is possible to assemble them into binary and ternary combinations.
Catalytic nanoparticles; TEM characterization; Zeta potential; Pt; Re; SnO2 NPs; Nanocolloids
Introduction
Nowadays, finding alternative sources of energy is an
important global issue
(dos Anjos et al. 2008; Li et al.
2013)
. The solution of this problem are ethanol fuel
cells, which become more and more popular. This is
related to the benefits of ethanol: it is less toxic
compared to methanol, easier stored and transported than
hydrogen, and available from renewable resources
(Li
et al. 2010; Du et al. 2011)
. However, the usage of
ethanol as fuel generates various challenges, such as
the difficulty to split the C–C bond and production of
many by-products
(Delpeuch et al. 2016)
. Therefore,
the key challenge is to design and develop the
appropriate type of catalysts. A good approach to obtain
highly selective and active electrocatalysts for ethanol
oxidation reaction (EOR), involves the preparation of
multifunctional and multicomponent nanostructured
particles
(Antolini 2007; Antolini and Gonzalez
2011; Goel and Basu 2012; Zhang et al. 2017)
. These
types of nanostructures are extensively synthesized
and studied because they exhibit interesting
properties, being key components in many catalytic
applications. Very important is the possibility of precisely
controlling the size, shape, and composition of the
synthesized nanoparticles. Because catalysis is a
surface effect, the catalyst needs to have the highest
possible surface area, which is related to the size
reduction (Sun et al. 2011). So far, the most promising
group of nanocatalysts for ethanol oxidation are
ternary catalysts based on mixtures of Pt, Rh, and SnO2
designed by the Adzic group
(Kowal et al. 2009b; Li
et al. 2010, 2013)
. This type of ternary nanocatalysts is
also studied by other groups
(Higuchi et al. 2014;
Delpeuch et al. 2016)
. This is related to the unique
and individual role of each component in the ethanol
oxidation pathway. The role of Rh is to cleave the C–C
bond in ethanol, while SnO2 provides OH species to
oxidize intermediates and to free Pt and Rh sites for
further ethanol oxidation (Li et al. 2013). Another
important issue mentioned above, is the physical
contact between the synthesized NPs. Kowal et al.
(2009a) studied ethanol oxidation reaction (EOR) on
ternary NP system containing Pt, Rh, and SnO2,
showing a higher activity of such system, because the
ethanol molecule has to be in contact with all the
phases of the catalyst, which allows for a complete
EOR. In their earlier work, they demonstrated the high
efficiency of the catalyst of the same composition
containing a Pt–Rh alloy
(Kowal et al. 2009b)
.
Another group
(Higuchi et al. 2014)
studied the Pt/Rh/
SnO2 catalyst, but they prepared a nanocatalyst only
with partial contact between the respective
nanoparticles. The authors confirmed that it is not clear, if for
EOR it is better to have a nanoalloy between the
metallic elements or is a physical contact between
them sufficient. The investigation by
Park et al.
(2008)
shows that the control of alloy composition
allows tuning the catalytic activity. On the other hand,
Roth et al. (2005)
indicate that alloy formation does
not seem to be a crucial requirement for a superior
electrocatalytic performance, as long as a close
contact between both phases is achieved. Therefore,
understanding the synergistic (...truncated)