High-performance CeO₂/rGO hybrid nanostructures as bifunctional electrocatalysts for water-splitting

Hydrogen-evolving material based on two-dimensional reduced graphene oxide with a rare-earth metal oxide such as ceria is relevant for water-splitting devices owing to greater electrocatalytic activity. Herein, a sustainable one-pot hydrothermal synthesis method was chosen to prepare a CeO₂/rGO nanostructure. The XRD pattern of CeO₂/rGO validated the intense peak at a 2θ value of 26.98°, revealing the formation of CeO₂ in the graphene layer in the CeO₂/rGO nanostructure. PL spectra showed a reduction in intensity for the CeO₂/rGO composite being indicative of strong interfacial interactions between CeO₂ nanoparticles and rGO. UV-visible spectra suggested higher absorption at 248 and 292 nm for the CeO₂/rGO composite because of the immobilization of rGO. FESEM of the CeO₂/rGO nanostructure disclosed that ceria was evenly aligned on rGO sheets around 20-30 nm in size and mapping analysis confirmed a more uniform distribution of elements. HR-TEM of CeO₂/rGO demonstrated the agglomerated carbon material surrounding CeO₂ with an average size of 27 nm with the formation of spherical CeO₂ nanoparticles. The CeO₂/rGO nanostructure had a Tafel slope of ∼168 mV dec^-1, which was comparatively smaller than that of CeO₂, rGO, and the bare NF electrode. The prepared nanostructure demonstrated an overpotential of 260 mV to attain a current density of -50 mA cm^-2, thereby establishing its superior catalytic activity towards water-splitting.