Most recently, iChEM researcher Prof. Yi Xie’s group made tremendous progress in “Ultrathin Co₃O₄ Layers Realizing Optimized CO₂ Electroreduction to Formate”, which was published on Angew. Chem. Int. Ed., 2015, DOI: 10.1002/anie.201509800.

Global warming and the energy crisis are two important issues we are facing in the 21st Century. Both problems are rooted in the unsustainable utilization of fossil fuels accompanied with release of greenhouse gas CO₂. In this regard, CO₂ reduction into useful fuels, powered by a renewable electricity source, could not only help to reduce CO₂ emission, but also decrease the energy shortage. Over the past three decades, researchers have evaluated lots of metals as electrodes for CO₂ reduction in aqueous solutions. While these metal electrodes show competent CO₂ electroreduction performances, they usually suffer from very high prices, limited availability, as well as rapid loss of CO₂ reduction activity, which seriously hinder their large-scale practical applications. To address these issues, several naturally abundant and chemically stable transition-metal oxides have been recently explored as potential CO₂ electroreduction catalysts to replace the expensive and easily deactivated metals. Among these materials, the spinel-type oxide of Co₃O₄ seems to be one of the most competitive candidates for electrocatalytic CO₂ reduction. In addition to being environmental friendly, having low cost and an abundance of reserves, the Co₃O₄ adopts a normal spinel structure with Co²⁺ ions in tetrahedral interstices and Co³⁺ ions in octahedral interstices, in which the peculiar crystal structure enables it to be high environmental stability. In spite of these advantages, the catalytic CO₂ reduction performance of Co₃O₄ is still far from satisfactory, which is primarily ascribed to the very low amount of active sites associated with poor electrical conductivity in previously fabricated Co₃O₄ catalysts. Henceforth, designing a suitable material with abundant active sites and high electrical conductivity holds the key to greatly promoting the electrocatalytic CO₂ reduction performances.



In their work, atomic layers for transition-metal oxides are proposed to address these problems through offering an ultralarge fraction of active sites, high electronic conductivity, and superior structural stability. As a prototype, 1.72 and 3.51 nm thick Co₃O₄ layers were synthesized through a fast-heating strategy. The atomic thickness endowed Co₃O₄ with abundant active sites, ensuring a large CO₂ adsorption amount. The increased and more dispersed charge density near Fermi level allowed for enhanced electronic conductivity. The 1.72 nm thick Co₃O₄ layers showed over 1.5 and 20 times higher electrocatalytic activity than 3.51 nm thick Co₃O₄ layers and bulk counterpart, respectively. Also, 1.72 nm thick Co₃O₄ layers showed formate Faradaic efficiency of over 60 % in 20 h. This work was published on top international journal (Angew. Chem. Int. Ed) and selected as Hot Papers.

http://onlinelibrary.wiley.com/wol1/doi/10.1002/anie.201509800/full