N-Doped Multi-shelled Ru-Co/Co3O4 Graphene-coated Nano- spheres as Bi-functional Electrocatalyst in Oxygen and Hydrogen Evolution Reactions

Abstract N-doped multi-shelled Ru-Co/Co3O4 graphene coated nano-spheres have been synthesized from metal organic frameworks (MOFs) using hydrothermal method. Annealing temperature of 250oC, 310oC, 380oC, 450oC and 530oC at heating rate of 2oC/min in presence of melamine under N2 atmosphere have resulted into multiple shell structured nano-spheres. Annealing temperature becomes the controlling factor in number of shell formation inside the nano-spherical materials and in better incorporation of nitrogen into the spherical structure. The present research work has shown the formation of quintupled shell structured nano-sphere at 530oC with greatest incorporation of nitrogen. Number of shell and nitrogen incorporation becomes the pivotal point of these materials’ electrocatalytic performance in water splitting. Therefore, quintupled shell structured nanospheres have shown remarkable electrocatalytic performance during water splitting with highest current density at lowest over-potential value in hydrogen and oxygen evolution reactions (HER and OER) under acidic media. Similarly, electrocatalytic activity gradually diminishes with decrease in the shell numbers inside nano-spheres.