Washington, Apr 19 : Chemists at the University of California, San Diego, claim to have developed a prototype device that can capture energy from the Sun, convert it to electrical energy and “split” carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2).

“For every mention of CO2 splitting, there are more than 100 articles on splitting water to produce hydrogen, yet CO2 splitting uses up more of what you want to put a dent into. It also produces CO, an important industrial chemical, which is normally produced from natural gas. So with CO2 splitting you can save fuel, produce a useful chemical and reduce a greenhouse gas,” said Clifford Kubiak, professor of chemistry and biochemistry at the university.

The device designed by Prof. Kubiak and his graduate student Aaron Sathrum to split CO2 utilizes a semiconductor and two thin layers of catalysts.

It splits CO2 to generate CO and O2 in a three-step process.

The first step is the capture of solar energy photons by the semiconductor. The second step is the conversion of optical energy into electrical energy by the semiconductor. The third step is the deployment of electrical energy to the catalysts.

The catalysts convert CO2 to CO on one side of the device and to O2 on the other side. As electrons are passed around in these reactions, a special type of catalyst that can convert electrical energy to chemical energy is required, said Prof. Kubiak.

Now his laboratory has created a large molecule with three-nickel atoms at its heart that has proven to be an effective catalyst for this process.

According to him, choosing the right semiconductor is also critical to making CO2 splitting practical.

Semiconductors have bands of energy to which electrons are confined. Sunlight causes the electrons to leap from one band to the next creating an electrical energy potential. The energy difference between the bands—the band gap—determines how much solar energy will be absorbed and how much electrical energy is generated.

Initially, the team used a silicon semiconductor to test the merits of their device. However, silicon absorbs light in the infrared range, and the conversion of sunlight by silicon, supplies about half of the energy needed to split CO2.

The team is now building the device using a gallium-phosphide semiconductor, which has twice the band gap of silicon and absorbs more energetic visible light.

They believe this will absorb the optimal amount of energy from the Sun to drive the catalytic splitting of CO2. (ANI)