University of Texas researchers develop new solar photoelectrosynthetic process to convert CO2 to methanol
Researchers from The University of Texas at Arlington are developing a new process for photoelectrosynthesis of methanol—the conversion of carbon dioxide to methanol using sunlight and hybrid CuO–Cu2O semiconductor nanorod arrays.
Solar photoelectrosynthesis of methanol was driven on hybrid CuO–Cu2O semiconductor nanorod arrays for the first time at potentials 800 mV below the thermodynamic threshold value and at Faradaic efficiencies up to 95%. The CuO–Cu2O nanorod arrays were prepared on Cu substrates by a two-step approach consisting of the initial thermal growth of CuO nanorods followed by controlled electrodeposition of p-type Cu2O crystallites on their walls.
No homogeneous co-catalysts (such as pyridine, imidazole or metal cyclam complexes) were used contrasting with earlier studies on this topic using p-type semiconductor photocathodes. The roles of the core–shell nanorod electrode geometry and the copper oxide composition were established by varying the time of electrodeposition of the Cu2O phase on the CuO nanorod core surface.—Ghadimkhani et al.
The process is safer, simpler and less expensive than previous methods to convert CO2 to a useful product, said Krishnan Rajeshwar, interim associate vice president for research at UT Arlington and one of the authors of a paper recently published in the RSC journal Chemical Communications.
Researchers began by coating the walls of copper oxide (CuO) nanorods with crystallites made from another form of copper oxide, Cu2O. In the lab, they submerged those rods in a water-based solution rich in CO2. Irradiating the combination with simulated sunlight created a photoelectrochemical reduction of the CO2 and that produced methanol.
In contrast, current methods require the use of a co-catalyst and must be conducted at high operating pressures and temperatures. Many also use toxic elements, such as cadmium, or rare elements, such as tellurium, Rajeshwar said.
As long as we are using fossil fuels, we’ll have the question of what to do with the carbon dioxide. An attractive option would be to convert greenhouse gases to liquid fuel. That’s the value-added option.—Krishnan Rajeshwar
Ghazaleh Ghadimkhani, Norma R. de Tacconi, Wilaiwan Chanmanee, Csaba Janaky and Krishnan Rajeshwar (2013) Efficient solar photoelectrosynthesis of methanol from carbon dioxide using hybrid CuO–Cu2O semiconductor nanorod arrays. Chem. Commun., 49, 1297-1299 doi: 10.1039/C2CC38068D