Selectivity-Enhanced Electroreduction of CO2 to CO at Novel Ru Linked-GO Nanohybrids: the Role of Nanoarchitecture

Abstract

Recently, global-scale efforts have been conducted for the electroreduction of CO2 as a potentially beneficial pathway for the conversion of greenhouse gases to useful chemicals and renewable fuels. This study focuses on the development of selective and sustainable electrocatalysts for the reduction of aqueous CO2 to CO. A RuIIcomplex [Ru(tptz)(ACN)Cl2] (RCMP) (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine, ACN = acetonitrile) was prepared as a molecular electrocatalyst for the CO2 reduction reaction in an aqueous solution. Density functional theory-calculated frontier molecular orbitals suggested that the tptz ligand plays a key role in dictating the electrocatalytic reactions. The RCMP electrocatalyst was grafted onto the graphene oxide (GO) surface both noncovalently (GO/RCMP) and covalently (GO-RCMP). The field emission scanning electron microscopy and elemental distribution analyses revealed the homogeneous distribution of the complex onto the GO sheet. The photoluminescence spectra confirmed accelerated charge-transfer in both nanohybrids. Compared to the bare complex, the GO-RCMP and GO/RCMP nanohybrids showed enhanced electrocatalytic activity, achieving >95% and 90% Faradaic efficiencies for CO production at more positive onset potentials, respectively. The GO-RCMP nanohybrid demonstrated outstanding electrocatalytic activity with a current of ∼84 μA. The study offers a perspective on outer- and inner-sphere electron-transfer mechanisms for electrochemical energy conversion systems.