Synergistic effect of cobalt-reduced graphene oxide hybrid for enhanced hydrogen evolution reaction

The Co-rGO hybrid exhibits a notable integration of cobalt nanoparticles (Co NPs) and reduced graphene oxide (rGO), leveraging their synergistic properties to enhance the hydrogen evolution reaction (HER) efficiency. This study presents a thorough synthesis and characterization of rGO-functionalized Co NPs, employing a one-pot approach where citric acid and hydrazine hydrate serve as reducing and capping agents for graphene oxide (GO) and Co NPs, respectively. Scanning electron microscopy (SEM) confirmed that the 2D rGO sheets effectively mitigated Co NP agglomeration, resulting in an average particle size of around 8 nm. X-ray diffraction (XRD) analysis validated the formation of Co NPs and indicated the presence of cobalt oxide (Co₃O₄ NPs). To assess HER performance, glassy carbon electrode (GCE) modified with rGO, Co NPs, and the Co-rGO hybrid were analyzed. The Co-rGO/GCE displayed an 18-fold increase in double-layer capacitance compared to the rGO/GCE. Additionally, the Co-rGO/GCE achieved a lower Tafel slope of 75 mV/dec, outperforming both Co/GCE (105 mV/dec) and rGO/GCE (115 mV/dec), highlighting significantly improved catalytic kinetics. Chronoamperometry tests demonstrated the Co-rGO hybrid's robust long-term stability for HER, maintaining catalytic activity over extended durations. These findings imply that the incorporation of nanosized cobalt and cobalt oxide on the rGO surface and edges effectively enhances the density of catalytically active sites, thereby augmenting the hybrid's synergistic characteristics for HER. This comprehensive investigation provides key insights for the design and advancement of nanomaterials aimed at improving electrocatalyst performance for various applications.