CLEANING THE WATER
Nuclear power also uses heat to generate electricity. A clean energy resource, nuclear energy originates from the splitting of uranium atoms in a process called fission. This generates heat to produce steam, which a turbine generator converts to electricity. While some consider nuclear power to be a sustainable energy source that reduces carbon emissions, others remember Chernobyl or the 2011 earthquake that shook Okuma, Japan, and caused a meltdown of the Fukushima Daiichi Nuclear Power Plant, leaving millions of gallons of contaminated water and no viable way to clean it up.
But chemistry professor Stephen Creager, along with the Savannah River National Laboratory (SRNL), is working on a way to fix that.
The SRNL is one of two facilities in the United States that stores the majority of the country’s nuclear waste. The lab is part of the Department of Energy and seeks to understand how to dispose of or repurpose tritium — an unstable, radioactive form of hydrogen that is a byproduct of nuclear reactors — by separating tritium ions from hydrogen ions. The answer may be a thin material called graphene.
The 2010 Nobel Prize for Physics was awarded for graphene, which has exceptional properties as a result of its being so thin.
“People had been saying for years that graphene was an impenetrable barrier and that the only way you could use it was to put holes in it,” says Creager. “But in 2014, this group out of England, one of the co-awardees of the 2010 Nobel Prize, reported that graphene was permeable to protons, which was a bombshell kind of report.”
When it was conveyed two years later that protons go through graphene 10 times faster than deuterons (the nuclei of deuterium, another form of hydrogen), Creager and SRNL decided to test it out for their purposes of separating tritium.
The team plans to build an electrochemical cell that can clean tritium out of contaminated water using water electrolysis. Contaminated water would flow in one side, and an added graphene layer would collect deuterium and tritium on the water side of the cell, allowing only pure hydrogen on the other side.
This process could also potentially be significant for energy conversion in fuel cells, which converts hydrogen and oxygen into water, and in the process, produces electricity. Fuel cells consist of an anode, a cathode and a membrane that allows protons to move between the two sides of the fuel cell. At the anode, a catalyst causes the fuel to undergo oxidation reactions that generate protons (positively charged hydrogen ions) and electrons. The protons flow from the anode to the cathode through the membrane. At the same time, electrons are drawn from the anode to the cathode through an external circuit, producing electricity. At the cathode, another catalyst causes hydrogen ions, electrons and oxygen to react, forming water.
These cells contain a membrane that must not only keep the hydrogen and oxygen separate, but also must allow protons to go through very fast. “That’s difficult,” Creager says. “Part of what’s exciting about these results is that the graphene should do this. It should allow protons to go through at really high rates without any impediment, but it will completely block everything else.”
Cassandra Hager is currently working with Creager as a doctoral student in the chemistry department, focusing on synthesizing polymeric materials, or plastics, for application in many different fields. Some of her research involves the improvement of fuel cell technology that operates with a proton exchange membrane. This type of fuel cell uses hydrogen as fuel and creates water as a by-product.
“The idea of utilizing a technology that decreases carbon emissions, with an output of simply water, was fascinating to me,” Hager says. “This type of research can be applied as a more eco-friendly option to the gasoline-fueled cars of today, and this is phenomenal because of the current problems with carbon emissions. But the application doesn’t stop there. Fuel cells can be utilized as an energy source for buildings, homes and even industry. The wide range of types of fuel cells allows for this to be possible. The versatility of the work and how helpful it could be draws me into the research.”
Ph.D. student and research assistant Bukola Saheed has also worked alongside Creager in fuel cell research. Saheed was recently awarded first place at Clemson’s fourth annual Graduate Research and Discovery Symposium for a poster presentation on miniaturized electrochemical cells. These cells are unique because they have a variety of practical and economical applications.
“Most of these kinds of studies are done by big industry,” Saheed says. “But we’ve made our research available to any electrochemistry lab. We’ve been able to come up with a new, miniaturized cell that will be relatively simple to produce and also cost effective.”
For Saheed, the best part of working on energy issues is developing new technology that’s applicable to the real world. “We can contribute to life positively, we can make our environment cleaner,” says Saheed. “An understanding of basic science can be applied to some of the challenges we see.”