| dc.description.abstract | Two fundamental steps are needed to halt or at least slowdown climate change. One is the
reduction of atmospheric carbon dioxide (CO2), and two is developing more efficient
renewable energy storage solutions. The electrocatalytic reduction of CO2 toward fuels or
valuable chemicals is a promising candidate to solve both problems. Copper (Cu) is a unique
catalyst capable of the electrocatalytic conversion of CO2 into a variety of carbon products
like methane (CH4), ethylene (C2H4), or formic acid (HCOOH). However, the low selectivity
towards C2 and C2+ products and the low stability of the bulk Cu catalyst complicate the
economic viability of the electrocatalytic reduction of CO2. The use of Cu nanostructures as
a catalyst has been shown to enhance the selectivity and the faradaic efficiency (FE) of the
electrocatalysis due to the increased catalyst’s surface area and the control of the exposed
Cu facets. Exposure of the Cu (100) facets in the catalyst’s surface has been demonstrated
to enhance the FE for C2 products, especially ethylene. During our research, we used a
colloidal approach to synthesize Cu nanowires (NWs) with exposed (100) facets. However,
a side nucleation of nanoparticles (NPs) was observed in all cases. Adjusting the synthesis
parameters, we were able to control not only the length and thickness of the NWs but also
the size and structure of the side nucleation. Little to no research has been done on the
impact on selectivity and stability of combining different Cu nanocrystals, nanocrystals with
different shape, size, and exposed facets. By controlling the concentration of ligands during
the colloidal synthesis, we were able to produce three different Cu catalysts: NWs with a
diameter of 30 nm and multi–shaped NPs, 30 nm NWs with nanopyramids and 40 nm NWs
with multi–shaped NPs. After modifying the NP’s concentration of the three different
catalysts and comparing its electrocatalytic performance, we were able to show the impact
of the NPs over the selectivity of the NWs. It has been revealed that a high concentration of
NPs, in the case of 30 nm NWs with multi–shaped NPs and 30 nm NWs with nanopyramids,
increases the selectivity towards ethylene and the stability of the catalyst. This increment is
due to the creation of CO* intermediate over the NPs´ surface and its transfer to the NWs
for its reduction to ethylene. The results of this research are promising with a maximum
selectity towards, however, there is a need for more research to understand the mechanism
of this synergy and how to optimize it | |
