Magnesium substituted cobalt spinel nanostructures for electrocatalytic water oxidation

Two MgCo2O4 nanostructures in different morphologies have been synthesized by using two different structure-directing agents (urea (U) and nitrilotriacetic acid (NTA)) as new catalysts for water oxidation reactions. The properties of these nanostructures were discovered and characterized by a combination of analytical techniques, being TEM, SEM, EDX, XRD, XPS, and BET. While the urea-stabilized MgCo2O4 (U-MgCo2O4) nanostructures have spiky morphology, the NTA-stabilized ones (NTA-MgCo2O4) have wire-like structures. The synthesized nanostructures were utilized to modify glassy carbon electrodes (GCEs), and the electrochemical activities of the modified electrodes in water oxidation reactions were investigated in an alkaline medium by recording linear sweep voltammograms (LSVs). Even though both modified GCEs had almost the same onset potentials (1.67V vs. RHE for U-MgCo2O4/GCE and 1.63V vs. RHE for NTA-MgCo2O4/GCE), NTA-MgCo2O4/GCE required a lower overpotential (463mV vs. 573mV) to drive 10 mA cm(-2) catalytic current density. Besides being catalytically more active than U-MgCo2O4/GCE, NTA-MgCo2O4/GCE was also found to be more stable in constant potential electrolysis. Moreover, it demonstrated a comparable performance to that of RuO2 and has the advantage of being significantly economic.