Electrochemical CO 2 reduction (ECR) to value-added fuels and chemicals provides a ''clean'' and efficient way to mitigate energy shortages and to lower the global carbon footprint. The unique structures of two-dimensional (2D) nanosheets and their tunable electronic properties make these nanostructured materials intriguing in catalysis. Various 2D nanosheets are showing promise for CO 2 reduction, depending on the preferred reaction product (HCOOH, CO, CH 4 , CH 3 OH, or CH 3 COOH). In this review, we focus on recent progress that has been achieved in using these 2D materials for ECR. We highlight procedures available for tuning catalytic activities of 2D materials and describe the fundamentals and future challenges of CO 2 catalysis by 2D nanosheets.

Cyclohexanone is an industrially important intermediate in the synthesis of materials such as nylon, but preparing it efficiently through direct hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Here we report that a previously unappreciated combination of two common commercial catalysts-nanoparticulate palladium (supported on carbon, alumina, or NaY zeolite) and a Lewis acid such as AlCl3-synergistically promotes this reaction. Conversion exceeding 99.9% was achieved with >99.9% selectivity within 7 hours at 1.0-megapascal hydrogen pressure and 50 degrees C. The reaction was accelerated at higher temperature or in a compressed CO(2) solvent medium. Preliminary kinetic and spectroscopic studies suggest that the Lewis acid sequentially enhances the hydrogenation of phenol to cyclohexanone and then inhibits further hydrogenation of the ketone.