Atomically dispersed Ru supported on microporous CoO ultrathin nanosheets synthesized by melamine induction for a highly efficient oxygen evolution reaction

Two dimensional materials show unique advantages in catalysis. In this work, it was found that melamine could induce the directional growth of cobalt-based catalysts to form an ultra-thin two-dimensional hexagonal nanosheet structure with only 1.5 nm. In addition, these hexagonal nanosheets (HNs) could grow into a microporous structure under high temperature conditions, and the finally formed CoO hexagonal porous nanosheets (HPNs) had a surface area 11.3 times that of the nanoparticles. Embedding 1.25 wt% of monoatomic ruthenium in the CoO HPNs (CoO/Ru-1.25% HPNs) allowed the catalyst to have more active charge storage and transfer centers. The results showed that the overpotential of CoO/Ru-1.25% HPNs was 64 mV lower than that of CoO nanoparticles at 10 mA cm(-2). The Tafel slope of CoO/Ru-1.25% HPNs was only half that of CoO nanoparticles, indicating that a small amount of Ru dispersion and the two-dimensional structure control significantly increased the kinetic rate in the oxygen evolution reaction. The DFT results showed that the Ru single atoms in CoO/Ru HPNs (111) possessed the lowest energy barrier (1.19 eV). The Ru single atoms could effectively reconstruct the neighboring localized structure in the formation of OOH, which desirably decreased the free energy of the system.