3D semiconductor particles offer 2D properties

Date:
January 3, 2022
Source:
Cornell University
Summary:
Researchers have discovered that the junctures at the facet edges
of 3D semiconductor particles have 2D properties, which can be
leveraged for photoelectrochemical processes -- in which light is
used to drive chemical reactions -- that can boost solar energy
conversion technologies.



FULL STORY ==========================================================================
When it comes to creating next-generation electronics, two-dimensional semiconductors have a big edge. They're faster, more powerful and more efficient. They're also incredibly difficult to fabricate.


========================================================================== Three-dimensional semiconductor particles have an edge, too --
many of them - - given their geometrically varied surfaces. Cornell
researchers have discovered that the junctures at these facet edges have
2D properties, which can be leveraged for photoelectrochemical processes
-- in which light is used to drive chemical reactions -- that can boost
solar energy conversion technologies.

This research, led by Peng Chen, the Peter J.W. Debye Professor of
Chemistry in the College of Arts and Sciences, could also benefit
renewable energy technologies that reduce carbon dioxide, convert nitrogen
into ammonia, and produce hydrogen peroxide.

The group's paper, "Inter-Facet Junction Effects on Particulate Photoelectrodes," published Dec. 24 in Nature Materials. The paper's
lead author is postdoctoral researcher Xianwen Mao.

For their study, the researchers focused on the semiconductor bismuth
vanadate, particles of which can absorb light and then use that energy
to oxidize water molecules -- a clean way of generating hydrogen as well
as oxygen.

The semiconductor particles themselves are anisotropically-shaped;
that is, they have 3D surfaces, full of facets angled toward each other
and meeting at edges on the particle surface. However, not all facets
are equal. They can have different structures that, in turn, result in different energy levels and electronic properties.

"Because they have different energy levels when they join at an edge,
there's a mismatch, and the mismatch gives you a transition," Chen
said. "If you had a pure metal, it wouldn't have this property." Using a
pair of high-spatial-resolution imaging techniques, Mao and Chen measured
the photoelectrochemical current and surface reactions at multiple
points across each facet and the adjoining edge in between, and then
used painstaking quantitative data analysis to map the transition changes.

The researchers were surprised to find that the three-dimensional
particles can actually possess the electronic properties of
two-dimensional materials, in which the transition happens gradually
across the so-called transition zone near the edge where the facets
converge -- a finding that had never been envisioned and could not have
been revealed without high-resolution imaging.

Mao and Chen hypothesize the width of the transition zone is comparable
to the size of the facet. That would potentially give researchers a
way to "tune" the electronic properties and customize the particles for photocatalytic processes.

They could also tune the properties by changing the widths of the
near-edge transition zones via chemical doping.

"The electronic property is dependent on which two facets are converging
at an edge. Now, you basically can design materials to have two desired
facets merge.

So there's a design principle," Chen said. "You can engineer the
particle for better performance, and you can also dope the material
with some impurity atoms, which changes the electronic property of each
facet. And that will also change the transition associated with this inter-facet junction. This really points to additional opportunities for three-dimensional semiconductor particles." The research was supported
by the U.S. Department of Energy's Office of Science -- Basic Energy
Sciences, Catalysis Science program. The researchers made use of the
Cornell Center for Materials Research, which is supported by the National Science Foundation.

========================================================================== Story Source: Materials provided by Cornell_University. Original written
by David Nutt. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Xianwen Mao, Peng Chen. Inter-facet junction effects on particulate
photoelectrodes. Nature Materials, 2021; DOI:
10.1038/s41563-021-01161-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220103121723.htm
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