Light-Driven Reaction Converts Carbon Dioxide Into Fuel

Light-Driven Reaction Converts Carbon Dioxide Into Fuel
Duke University researchers have engineered rhodium nanoparticles (blue) that can harness the energy in ultraviolet light and use it to catalyze the conversion of carbon dioxide to methane, a key building block for many types of fuels. Credit: Chad Scales

A previous research showed that carbon dioxide from the air can transform into methanol. Methanol is used as cleanest burning fuel and help to minimize toxic carbon dioxide from the atmosphere. This time scientists from the Duke University have developed tiny nanoparticles that help convert carbon dioxide into methane. This catalyst uses a light-driven reaction.

Through this light-driven reaction that uses ultraviolet light, scientists hope to develop a version that would run on natural sunlight.

Actually, scientists wanted to develop an efficient, light based catalyst to reduce the toxic level of carbon dioxide in the atmosphere. So, they decided to convert it into methanol which is a key building block for many types of fuels.

The catalyst strongly favoring the formation of methane instead of mixing methane and undesirable side-products like carbon monoxide. According to scientists, this strong selectivity also extends other essential chemical reactions. It also makes rhodium particles more efficient.

Associate professor Jie Liu said, “The fact that you can use light to influence a specific reaction pathway is very exciting. This discovery will really advance the understanding of catalysis.”

Scientists added some small amounts of the silvery gray metal to optimize a number of key industrial processes. For example, industries that make drugs, detergents, and nitrogen fertilizer. They also break down toxic pollutants in the catalytic converters of our cars.

Rhodium boosts such reactions that can be easily generated in the form of heat.

In the past two decades, scientists have explored new and useful ways that light can be used to add energy to bits of metal shrunk down to the nanoscale. This field is called a plasmonics.

Professor Henry Everitt said, “Effectively, plasmonic metal nanoparticles act like little antennas. They absorb visible or ultraviolet light very efficiently and can do a number of things like generating strong electric fields. For the last few years, there has been a recognition that this property might be applied to catalysis.”

Scientists then combined rhodium particles near an ultra violet light. They then placed small amounts of charcoal colored nanoparticles into a reaction chamber and passed mixtures of carbon dioxide and hydrogen through the powdery material. The nanoparticles are then placed for heating under 300-degree celsius. This reaction produces a poisonous gas. When the heat is turned off, the reaction almost exclusively produced methane.

Everitt said, “We discovered that when we shine the light on rhodium nanostructures, we can force the chemical reaction to go in one direction more than another. So we get to choose how the reaction goes with light in a way that we can’t do with heat.

This ability to control chemical reaction generates the desired product with little or no side-products.

Xiao Zhang, a graduate student said, “If the reaction has only 50 percent selectivity, then the cost will be double what it would be if the selectively is nearly 100 percent. And if the selectivity is very high, you can also save time and energy by not having to purify the product.”

Now scientists are planning to test light-driven reaction to manipulate other reactions that are currently catalyzed with heated rhodium metal.

Liu said, “Our discovery of the unique way light can efficiently, selectively influence catalysis came as a result of an on-going collaboration between experimentalists and theorists.”