Bifuntional petaloid nickel manganese layered double hydroxides decorated on a freestanding carbon foam for flexible asymmetric supercapacitor and oxygen evolution

In this work, we develop a bifunctional composite comprised of hierarchical flower-like NiMn-layered double hydroxides (LDH) nanoarrays grown on melamine sponge-derived carbon (SC). This composite material is used as a flexible asymmetric supercapacitor positive electrode and oxygen evaluation reaction (OER) electrocatalyst. Integrated carbon foams with controllable three-dimensional pores are easily obtained and served as conductive backbones for the growth of the flower-like NiMn-LDH nanoarrays. The as-prepared flexible electrode, combining a highly open scaffold-like structure with well-designed electron transfer channels, shows significantly enhanced cyclic stability (99.6% of the initial activity maintained after 5000 cycles) and high energy density (41.0 Wh·Kg−1) in aqueous electrolyte. The as-prepared SC@NiMn-LDH@G//NPC asymmetric supercapacitor can lighten a LED indicator for more than 10 minutes. Additionally, this composite presents extremely low overpotentials (220 mV at 10 mA·cm−2) and low Tafel slopes (30 mV·dec−1) in alkaline medium. This OER performance is one of the best reported so far among the state of art electrocatalysts.