properties. Graphene quantum dots absorb light of different
colors, which makes them useful for photocatalysis. In solar
cells, graphene quantum dots can be used as a photosensitizer
to efficiently enhance photoelectric conversion.
At NETL, researchers have successfully processed anthracite, bituminous and sub-bituminous coal samples from
regional partners in Wyoming, Kentucky, Virginia, and
Pennsylvania to manufacture small graphene quantum dots
suspended in water, without the need for surfactants or other
stabilizers. NETL researchers are now evaluating the use of
these materials as additives for cements and plastics.
Additional processing methods developed by NETL can
produce large, micron-sized graphene materials as dry, solid,
powders. These forms of graphene are being investigated for
use as electrode materials for batteries, water filtration materials and for chemical sensing applications.
Research at NETL is already illustrating how coal can make
a difference in the price of nanomaterials.
“We started with a coal feedstock costing about one penny,”
Matranga explained. “With just a few hours of processing we
converted this penny’s worth of coal into 1 liter of graphene
quantum dots in water, which has a current market value of
approximately $50,000. The work shows how dramatically
“Graphene nanomaterials are currently too expensive to use
in most commercial applications,” he said. “Our research is
illustrating that the manufacturing costs can be brought down
to levels comparable to other specialty additives used commer-
cially. Right now, there aren’t many graphene producers and
only one or so doing it with coal feedstocks, so these nano-
materials will continue to be expensive until there are more
manufacturers and competition in the marketplace.”
Applications for cement
These graphene quantum dots have value for another
specialty area for NETL researchers: wellbore cement.
“We’re evaluating how coal-based additives might enhance the mechanical properties and corrosion resistance of
wellbore cements for downhole applications, this approach
should also work for the conventional cement and concrete
used for roads and sidewalks,” Matranga said.
Wellbore materials must be resistant to chemical corrosion
from injected fluids, be sufficiently strong to withstand mechanical stresses associated with injection and have integrity
to prevent fluids from leaking out of the well into surrounding geological formations.
“Our current investigations are using coal-derived
graphene quantum dots as an additive in cement, and we find
that porosity and permeability decreased, which improves
corrosion resistance,” Matranga said.
The team also found that the mechanical properties of the
cement improve. Additional characterization is in progress, but based on these results, the team is optimistic that
coal-derived carbon materials could provide an affordable
Alternatives applications for domestic coal. Credit: National
Energy Technology Laboratory (NETL)
way to improve well-bore cements critical for protecting the
environment during oil and gas extraction.
NETL is working closely with private industry to build
upon its innovations. For example, in June 2018, NETL
launched a partnership with Ramaco Carbon to collaborate
on innovative projects that use coal as a manufacturing
feedstock for high-value products. A cooperative research
and development agreement (CRADA) signed June 7, 2018,
enhances NETL’s materials engineering and manufacturing
capabilities by allowing researchers access to the coal-based
manufacturing and research facilities being developed by
Ramaco Carbon near Sheridan, Wyoming.
Once completed, Ramaco Carbon will operate the world’s
only fully integrated coal-based research, development and
production facility. Ramaco areas of interest include the use
of coal to create carbon-based product precursors and resins,
rare earth elements from coal and coal by-products, feedstock
production for carbon-based products, and production of
advanced carbon materials—all areas in which NETL has extensive expertise. NETL researchers are working to establish
programmatic research activities in coal-based manufacturing
that will be aided by the agreement.
For more than 100 years, coal has dominated the nation’s
energy production, providing an affordable, reliable foundation
for prosperity. Now this abundant resource is opening new
doors as technology options find new applications that do not
require burning this resource and generating greenhouse gas.
As research and innovation continues to drive opportunities,
coal-based industries could provide a more affordable alternative
to the ubiquitous petroleum-based materials that are used to
make consumer products and specialty materials that are critical
for the United States’ energy independence and security.