MgCo2O4 nanostructures as cathode electrodes for perspective application in electrochemical CO2 pumping

Electrochemical gas pumping is an effective method for the recovery of hydrogen (H2) and, in the last decade, also for the capture of carbon dioxide (CO2) from the streams of plants fueled by carbon-based or gaseous fuels. Despite recent advances, electrocatalysts still need to be improved to prevent unwanted reactions and increase their activity. In this work, a MgCo2O4 spinel was synthesized and evaluated in an electrochemical system achieving a limiting current density of 4.1 mA cm-2 in the oxygen reduction reaction (ORR) and 4000 ppm in the electrochemical CO2 pumping device. In comparison, Pt reaches 5.1 mA cm-2 for the ORR and exceeds 6000 ppm on the permeate side. Physicochemical analysis by XRD revealed that the MgCo2O4 spinel has a face-centered cubic structure with a crystallite size of 11.27 nm. In addition, two morphologies were observed by TEM: larger particles resembling fullerenes and a nanostructure in the form of nanosheets. Finally, the XPS technique confirmed the presence of Mg2+ and Co3+ species in the MgCo2O4 spinel, along with surface defects such as oxygen vacancies.