2D material in three dimensions

Date:
January 31, 2022
Source:
Vienna University of Technology
Summary:
For years, scientists have tried to develop 2D-materials such as
graphene, which consists of only one layer of carbon atoms. But
what if you need to fit as much graphene as possible into a limited
space? Then the graphene layer has to be turned into a complex
3d shape.



FULL STORY ==========================================================================
The carbon material graphene has no well-defined thickness, it merely
consists of one single layer of atoms. It is therefore often referred
to as a "two- dimensional material." Trying to make a three-dimensional structure out of it may sound contradictory at first, but it is an
important goal: if the properties of the graphene layer are to be
exploited best, then as much active surface area as possible must be
integrated within a limited volume.


==========================================================================
The best way to achieve this goal is to produce graphene on complex
branched nanostructures. This is exactly what a cooperation between
CNR Nano in Pisa, TU Wien (Vienna) and the University of Antwerp has
now achieved. This could help, for example, to increase the storage
capability per volume for hydrogen or to build chemical sensors with
higher sensitivity.

From solid to porous In Prof. Ulrich Schmid's group (Institute for
Sensor and Actuator Systems, TU Wien), research has been conducted for
years on how to transform solid materials such as silicon carbide into extremely fine, porous structures in a precisely controlled way. "If
you can control the porosity, then many different material properties
can be influenced as a result," explains Georg Pfusterschmied, one of
the authors of the current paper.

The technological procedures required to achieve this goal are
challenging: "It is an electrochemical process that consists of several
steps," says Markus Leitgeb, a chemist who also works in Ulrich Schmid's research group at TU Wien.

"We work with very specific etching solutions, and apply tailored electric current characteristics in combination with UV irradiation." This allows
to etch tiny holes and channels into certain materials.

Because of this expertise in the realization of porous structures,
Stefan Heun's team from the Nanoscience Institute of the Italian National Research Council CNR turned to their colleagues at TU Wien. The Pisa
team was looking for a method to produce graphene surfaces in branched nanostructures to enable larger graphene surface areas. And the technology developed at TU Wien is perfectly suited for this task.

"The starting material is silicon carbide -- a crystal of silicon and
carbon," says Stefano Veronesi who performed the graphene growth at CNR
Nano in Pisa.

"If you heat this material, the silicon evaporates, the carbon remains
and if you do it right, it can form a graphene layer on the surface."
An electrochemical etching process was therefore developed at TU Wien that turns solid silicon carbide into the desired porous nanostructure. About
42 % of the volume is removed in this process. The remaining nanostructure
was then heated in high vacuum in Pisa so that graphene formed on the
surface. The result was then examined in detail in Antwerp. This revealed
the success of the new process: indeed, a large number of graphene flakes
form on the intricately shaped surface of the 3D nanostructure.

A lot of surface area in a compact form "This allows us to use the
advantages of graphene much more effectively," says Ulrich Schmid. "The original motivation for the research project was to store hydrogen:
you can temporarily store hydrogen atoms on graphene surfaces and then
use them for various processes. The larger the surface, the larger the
amount of hydrogen you can store." But there are also many other ideas
for using such 3D graphene structures. A large surface area is also a
decisive advantage in chemical sensors, which, for example, can be used
to detect rare substances in gases.

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


========================================================================== Journal Reference:
1. Stefano Veronesi, Georg Pfusterschmied, Filippo Fabbri, Markus
Leitgeb,
Omer Arif, Daniel Arenas Esteban, Sara Bals, Ulrich Schmid,
Stefan Heun.

3D arrangement of epitaxial graphene conformally grown on
porousified crystalline SiC. Carbon, 2022; 189: 210 DOI:
10.1016/j.carbon.2021.12.042 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220131110451.htm

--- up 8 weeks, 2 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)