Angew. Chem. Int. Ed. (2015)

Electroreduction of carbon dioxide to formate enables the storage of electricity in the form of chemical energy and can limit the release of greenhouse gases. Typically, the best electrocatalysts for such a reaction require expensive and scarce metals; thus, enhancing the performance of catalysts based on cheaper transition metal oxides is desirable. Now, Yi Xie, Yongfu Sun and colleagues at the University of Science and Technology of China in Hefei have shown that the electrocatalytic activity of thin layers of cobalt oxide can be greatly increased when their thickness is reduced to below 2 nm.

Credit: WILEY

The researchers found that the current density of 1.72-nm-thick layers increased by a factor of 20 relative to the bulk. The improvement was attributed in part to the high fraction of low-coordinate surface atoms, which provided more active sites for the adsorption of carbon dioxide. After normalizing the activity by the electrochemically active surface area, the intrinsic activity was found to increase with decreasing layer thickness. Computational results suggested that the thin layers had greater and more dispersed charge density at the Fermi level compared with the bulk, giving rise to higher conductivity that could in part explain the higher activity. The 1.72-nm-thick layers also had superior stability and Faradaic efficiency compared with layers having a thickness of 3.51 nm. These results suggest that reducing the thickness to the nanometre scale is a promising approach for designing electrocatalysts for the conversion of carbon dioxide to fuels.