Sustainable starfish like cobalt electrocatalyst grown on optimized CNT-graphene hybrid host for efficient water oxidation

Abstract

Solar energy generation is one of the most efficient approach to solve emerging environment and energy challenges. In this context, solar assisted dissociation of water into oxygen and hydrogen utilizing scalable and high performance electrocatalysts plays key role since the produced hydrogen is a clean energy carrier. Here, cobalt based nanoflakes with metallic core and oxidized surface were grown on the designed carbonaceous layer for anodic oxygen evolution reaction (OER) using an electrochemical approach. Carbonaceous layers containing proper amount of carbon nanotubes (CNT) and reduced graphene oxide (rGO) species were used to optimize the system. Although higher weight percent of rGO led to a more effective surface on the CNT-rGO layer for depositing Co electrocatalytic sites, the lowest overpotential value and charge transfer resistance were obtained for carbonaceous hybrids containing 50 wt% rGO in both CNT-rGO (315 mV, 388 Ω) and Co-deposited CNT-rGO (289 mV, 20 Ω) electrodes. The optimized rGO concentration also influenced cobalt growth mechanism which produced starfish like surface morphology covered by nano sized flakes. This hierarchical surface roughness created more catalytic active sites providing high electrical conductivity in the overall structure leading to an optimum Co-deposited CNT-rGO electrocatalysts for efficient water oxidation process.