Abstract
In the last few decades, renewable resources received considerable attention for the production of hydrogen. Herein, we present oxygen evolution from water using cobalt oxide based nanomaterials (Co3O4, Co3O4@SiO2, Co3O4/TiO2, Co3O4/Fe2O3 and ZnO@SiO2). These nanomaterials were grown in a controlled size and were characterized by various spectroscopic techniques. The Co3O4, Co3O4@SiO2, Co3O4/TiO2, Co3O4/Fe2O3, and ZnO@SiO2 were screened for their electro-catalytic properties towards H2O oxidation. All cobalt oxide based nanomaterials showed good oxygen evolution activity and high stability in alkaline conditions. However, Co3O4@SiO2 showed a higher current density at lower overpotentials and a lower Tafel slope (107.7 mV dec(-1)) as compared to Co3O4/TiO2, Co3O4/Fe2O3, ZnO@SiO2, and Co3O4. At 1.0 V (overpotential 735 V versus Ag/AgCl), Co3O4@SiO2 supplied a current density of 63.0 mA cm(-2) in 0.3 M KOH solution. This indicated a superior electrocatalytic performance then the other electrocatalyst. The excellent electrocatalytic performance of Co3O4@SiO2 might be due to certain structural features, which elevate its electrical conductivity, its oxidizing aptitude, and the affinity between OH- ions and the Co3O4@SiO2 surface and ultimately enhance smooth mass transports, which give superior oxygen evolution activity to Co3O4@SiO2.