Synergistic coupling of CoFe-layered double hydroxide nanosheet arrays with reduced graphene oxide modified Ni foam for highly efficient oxygen evolution reaction and hydrogen evolution reaction

Novel CoFe-LDH (layered double hydroxide) nanosheet arrays in situ grown on rGO (reduced graphene oxide) uniformly modified Ni foam were synthesized by a citric acid-assisted aqueous phase coprecipitation strategy. Systematic characterizations indicates that the series of CoxFe1-LDH/rGO/NF (x = 4, 3, 2) all show CoxFe1-LDH nanosheets (150–180 × 15 nm) grown vertically on the surface of rGO/NF. Especially, the Co3Fe1-LDH/rGO/NF exhibits the best performance with overpotentials of 250 and 110 mV at 10 mA cm−2 in 1 M KOH for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. When it is used as cathode and anode simultaneously for overall water splitting, they require 1.65 and 1.84 V at 10 and 100 mA cm−2, respectively. Excellent performance of Co3Fe1-LDH/rGO/NF is due to the nanosheet arrays structure with open channels, synergistic coupling between Co3Fe1-LDH and rGO enhancing electrical conductivity, and in-situ growth of Co3Fe1-LDH on rGO/NF enhancing stability.