Facile Synthesis of Rhodium Nanodendrites with Enhanced Activity toward Hydrazine-Assisted Water Splitting

We report an aqueous synthesis of Rhodium (Rh) nanodendrites and evaluation of their merit as a bifunctional electrocatalyst toward hydrazine-assisted water splitting. The formation of dendritic morphology can be attributed to the fast reduction kinetics responsible for burst nucleation and then attachment growth. Rapid reduction results in a high concentration of Rh atoms, which quickly nucleate and grow into ultrafine Rh nanocrystals, followed by their evolution into dendritic structures through attachment growth. Extending the reaction time naturally prolongs the number of branched arms while increasing the overall size of the particles. Aging the Rh-(III) precursor solution slows down the reduction kinetics, leading to the formation of fewer Rh nanoparticles for the generation of smaller dendrites. The reaction temperature influences the reduction kinetics during nucleation and then aggregation thermodynamics governing the attachment process. Together with a high specific surface area, the lattice defects arising from attachment growth induce tensile strain, resulting in more and better catalytic sites. When evaluated as a bifunctional electrocatalyst toward hydrazine oxidation and hydrogen evolution reactions, the Rh nanodendrites gave an enhanced mass activity of 162.0 A mg^-1 at 0.20 V vs RHE for hydrazine oxidation and 8.6 A mg^-1 at -0.07 V vs RHE for hydrogen evolution, approximately 1.5 times greater than that of 5 nm Rh nanocubes, highlighting their promise for applications such as hydrazine-assisted water splitting.