Effective pathway to convert CO2 into ethylene

Date:
September 17, 2020
Source:
University of California - Los Angeles
Summary:
The scientists developed nanoscale copper wires with specially
shaped surfaces to catalyze a chemical reaction that reduces
greenhouse gas emissions while generating ethylene -- a valuable
chemical simultaneously.



FULL STORY ==========================================================================
A research team from Caltech and the UCLA Samueli School of Engineering
has demonstrated a promising way to efficiently convert carbon dioxide
into ethylene -- an important chemical used to produce plastics, solvents, cosmetics and other important products globally.


==========================================================================
The scientists developed nanoscale copper wires with specially shaped
surfaces to catalyze a chemical reaction that reduces greenhouse
gas emissions while generating ethylene -- a valuable chemical
simultaneously. Computational studies of the reaction show the shaped
catalyst favors the production of ethylene over hydrogen or methane. A
study detailing the advance was published in Nature Catalysis.

"We are at the brink of fossil fuel exhaustion, coupled with global
climate change challenges," said Yu Huang, the study's co-corresponding
author, and professor of materials science and engineering at
UCLA. "Developing materials that can efficiently turn greenhouse gases
into value-added fuels and chemical feedstocks is a critical step to
mitigate global warming while turning away from extracting increasingly
limited fossil fuels. This integrated experiment and theoretical
analysis presents a sustainable path towards carbon dioxide upcycling
and utilization." Currently, ethylene has a global annual production
of 158 million tons. Much of that is turned into polyethylene, which
is used in plastic packaging. Ethylene is processed from hydrocarbons,
such as natural gas.

"The idea of using copper to catalyze this reaction has been around for
a long time, but the key is to accelerate the rate so it is fast enough
for industrial production," said William A. Goddard III, the study's co-corresponding author and Caltech's Charles and Mary Ferkel Professor
of Chemistry, Materials Science, and Applied Physics. "This study shows
a solid path towards that mark, with the potential to transform ethylene production into a greener industry using CO2 that would otherwise end
up in the atmosphere." Using copper to kick start the carbon dioxide
(CO2) reduction into ethylene reaction (C2H4) has suffered two strikes
against it. First, the initial chemical reaction also produced hydrogen
and methane -- both undesirable in industrial production. Second, previous attempts that resulted in ethylene production did not last long, with conversion efficiency tailing off as the system continued to run.

To overcome these two hurdles, the researchers focused on the design
of the copper nanowires with highly active "steps" -- similar to a set
of stairs arranged at atomic scale. One intriguing finding of this collaborative study is that this step pattern across the nanowires'
surfaces remained stable under the reaction conditions, contrary to
general belief that these high energy features would smooth out. This
is the key to both the system's durability and selectivity in producing ethylene, instead of other end products.

The team demonstrated a carbon dioxide-to-ethylene conversion rate of
greater than 70%, much more efficient than previous designs, which yielded
at least 10% less under the same conditions. The new system ran for 200
hours, with little change in conversion efficiency, a major advance for copper-based catalysts. In addition, the comprehensive understanding of
the structure-function relation illustrated a new perspective to design
highly active and durable CO2 reduction catalyst in action.

Huang and Goddard have been frequent collaborators for many years, with Goddard's research group focusing on the theoretical reasons that underpin chemical reactions, while Huang's group has created new materials and
conducted experiments. The lead author on the paper is Chungseok Choi,
a graduate student in materials science and engineering at UCLA Samueli
and a member of Huang's laboratory.


========================================================================== Story Source: Materials provided by
University_of_California_-_Los_Angeles. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Chungseok Choi, Soonho Kwon, Tao Cheng, Mingjie Xu, Peter Tieu,
Changsoo
Lee, Jin Cai, Hyuck Mo Lee, Xiaoqing Pan, Xiangfeng Duan, William A.

Goddard, Yu Huang. Highly active and stable stepped Cu surface for
enhanced electrochemical CO2 reduction to C2H4. Nature Catalysis,
2020; DOI: 10.1038/s41929-020-00504-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917084058.htm

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