Ni Nanoparticle-catalyzed CO₂ Methanation

By Momodou Salieu Sowe, UVA ChemSciComm

These summaries describe a research project for five different levels of understanding, going from primary school to expert.

Primary School:

The air has different things in it, and one of those things is called carbon dioxide, or CO₂ for short. We generate CO₂ using automobiles, running factories, and producing electricity. When we make too much CO₂, it goes up into the sky and wraps around our Earth like a warm blanket. This blanket captures heat energy that can make the Earth warmer and cause problems like melting ice, hot days, and even bad storms. So, we need to reduce CO₂ in our atmosphere, which means we need to produce less CO₂, like how we currently make energy. We can also find ways to turn CO₂ into something like the gasoline we use for cars, recycling it from the atmosphere. My research is to find ways to turn CO₂ into useful molecules since that way this is one way to keep the planet healthy for everyone and all the animals and plants that live on it.

Secondary School:

CO₂ is a waste product from the energy we produce, the concrete we use for buildings, and the chemicals we produce like plastics, paints, and fabrics. We must identify ways to stop CO₂ release into the environment and discover new methods to recycle it, just like we do with glass and plastic bottles. Earth’s atmosphere is comparable to sitting in a car on a hot summer’s day: if the windows are closed, and air does not circulate, the energy going into the car is greater than what is released, causing the internal temperature to rise rapidly. As the amount of CO₂ in our planet's atmosphere rises, a similar effect occurs, as increased amounts of energy are radiated back to the planet's surface rather than being released into space. We can recycle the excess CO₂ and convert it into something that helps our world flourish, if we design new chemical processes. My research interest is to turn CO₂ into something useful like methane gas for energy, which could create a cycle where no new CO₂ is released, freeing us from consuming gas and oil from nonrenewable sources. 

College:

Carbon dioxide (CO₂), a greenhouse gas, absorbs infrared energy in the atmosphere and contributes to climate change. Human activities like burning fossil fuels (coal, oil, and natural gas) and deforestation are the main contributors to CO₂ emissions. As a result of human activity, which emits more CO₂ into the atmosphere than natural processes can absorb, the amount in the atmosphere increases yearly. My research is to convert CO₂ into synthetic methane with nickel (Ni) catalysts. Synthetic methane is obtained from combining CO₂ with hydrogen gas in the presence of metal catalysts, which facilitate more rapid chemical transformations. Synthetic methane could replace nonrenewable fossil fuels and reduce high CO₂ emissions from burning fossil fuels. Reducing the atmospheric concentrations of CO₂ by closing the emissions cycle will help to address the negative impacts of climate change sustainably.

Graduate Student in the Discipline:

CO₂ emissions from fossil fuels and industrial processes have increased atmospheric CO₂ concentrations. We need sustainable approaches to control emissions and reduce the carbon footprint. A promising approach so far is the process of carbon recycling. Thermal-catalyzed reactions have been studied for CO₂ methanation with H₂ using precious metals such as Pt and Pd. These metals are important because of their high electron density that enhances the π-bond dissociation necessary for the reduction of CO₂; however, their scarcity makes their use cost-prohibitive. Phosphorous-containing ligands are effective in tuning the morphology of nickel catalysts to achieve analogous reactivity to Pt and Pd, however, recent studies have shown induced evolution by phosphorous contamination of active sites even after annealing at high temperatures. My research goal is to synthesize low-cost Ni catalysts with tunable morphology from phosphorous-free ligands to mediate CO₂ methanation in the presence of H₂. To achieve this, I am testing surfactants such as oleylamine, which is easy to remove from the surface of nanoparticles by thermal annealing, thereby preventing catalyst restructuring.   

Expert in the Field:

CO₂ is the leading greenhouse gas emitted into our atmosphere. Efficient thermal catalytic processes are needed to reduce CO₂ to synthetic methane, which would be an alternative to nonrenewable fossil fuels and address concerns about atmospheric CO₂ concentrations. Nanoparticle catalysts have shown promising activity because of their high intrinsic surface areas and the ability to synthesize specific shapes with desired active site morphologies. Phosphorous-containing ligands are widely used surfactants in nanoparticle synthesis to precisely control particle size and shape. However, our lab has shown that trioctylphosphine and tributylphosphine-capped nickel nanoparticles induce surface evolution, leading to higher rates of undesirable CO formation during CO₂ methanation with H₂. The surface evolution is attributed to phosphorous contamination of active surface sites. My research focuses on nickel nanoparticle synthesis from surfactants such as oleylamine, which is easily removed by thermal annealing to achieve tunable nickel particle size and shape for CO₂ methanation, with the goal of making the particles resistant to morphological changes during catalysis.