(770d) One-Step Synthesis of Monodispersed Cocu Core-Shell Nanoparticles with Solid Solution Shells

CORE-SHELL CoCu NANOPARTICLES FOR FISCHER-TROSCH SYNTHESIS

Cun Wen,
University of South Carolina, Columbia, SC

Jason Hattrick-Simpers, University of
South Carolina, Columbia, SC

Jochen
Lauterbach, University of South Carolina, Columbia, SC

The rising concerns about petroleum reserve depletion have placed
alternative energies under the spotlight of recent research. One possible
alternative is to convert coal or biomass feedstocks
into carbonaceous fuels using Fischer-Tropsch
Synthesis (FTS). [1]
To fuel diesel engines, fuel cells, and jet turbines, different types of fuels
are needed, which require different product selectivity in FTS. The selectivity
in FTS can be adjusted by choosing appropriate metals as the active component;
further control can be exerted by fine tuning the electronic structure via
doping. Cobalt is considered to be one of the most promising catalysts for FTS,
although it is expensive compared to Fe-based catalysts. The selectivity of
cobalt catalyst can be tuned by doping with other metals, such as Cu and Ru, to form catalytically active alloys.[2] Thus, a core-shell structured nanoparticle
with alloy of Co and Cu on the shell and the Cu as the core would be both
active for the FTS and also low in cost. However, traditionally two steps are
needed to prepare core-shell structures to maintain tight control of the
morphology and size, first forming the core of the nanoparticles and then
coating the core with the other component as the shell. Furthermore, the two
step method results in a mono-metallic surface rather than presenting a solid
solution of two metals on the surface.

Herein, we demonstrate a novel one-step synthesis methodology for monodispersed non-noble transition metal core-shell
nanoparticles where both the core and the shell are composed of a solid
solution of the two metals. The TEM image and the size distribution of CoCu core-shell nanoparticles are shown in figure 1. Along
with the increase of Cu content in the CoCu
nanoparticles from 10 to 20 atomic percent, the product selectivity is shifted
from long hydrocarbons (gasoline/diesel for cars) to lower hydrocarbons
(LPG-like gas for fuel cells). However, these phenomena are not observed in
catalysts obtained from impregnation methods with the same compositions. Though
the wet impregnation is widely used in practical application because of low
cost, the one-step synthesis method of core-shell nanoparticles is also economically
viable and up-scalable. Thus, the one-step methodology opens an avenue for
efficiently but viably tuning product distribution for industrial FTS plants.

Fig. 1. TEM image and size distribution of the CoCu nanoparticles

References

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Galvis HM, Bitter JH, Khare
CB, Ruitenbeek M, Dugulan
AI, de Jong KP. Supported Iron Nanoparticles as Catalysts for
Sustainable Production of Lower Olefins. Science.
2012;335(6070):835-838.

2.  Iglesia E, Soled SL, Fiato RA, Via GH. Bimetallic Synergy in
Cobalt Ruthenium Fischer-Tropsch Synthesis Catalysts.
J Catal. 1993;143(2):345-368. ADDIN EN.REFLIST