Design of a High-Efficiency Bifunctional Electrocatalyst: Rich-Nitrogen-Doped Reduced Graphene Oxide-Modified Carbon Cloth-Growing Nickel-Iron Complex Oxides for Overall Water Splitting

The rapid development of high-efficiency and low-price bifunctional electrocatalysts for replacing precious metalcatalysts has been confronted with an enormous challenge for theoxygen evolution reaction (OER) and hydrogen evolution reaction(HER). Here, a three-dimensional cubic electrocatalyst of nickel-iron complex oxides grown on the rich-nitrogen-doped reducedgraphene oxide (NiFe2O4@N-rGO-CC) was synthesized throughthe two-step hydrothermal reaction. The experimental integrity testrevealed that NiFe2O4@N-rGO-CC exhibited excellent electro-catalytic performance and long-term stability in both alkaline andacid electrolytes. In a 1.0 M potassium hydroxide (KOH) solution,lower overpotentials of 479 and 156 mV were acquired to deliverthe current density of 10 mAmiddotcm-2for both OER and HER,respectively. Besides, NiFe2O4@N-rGO-CC also exhibited excellent HER performance in 0.5 M H2SO4solution, which provided alower overpotential of 188 mV with a current density of 10 mAmiddotcm-2. NiFe2O4@N-rGO-CC showed extremely stable durability overa long time period of 30 h for OER and 50 h for HER in alkaline medium, and 40 h for HER in acid medium. Furthermore,NiFe2O4@N-rGO-CC required only 1.67 V to deliver the current density of 10 mAmiddotcm-2for alkaline water splitting, and it could bemaintained for up to 70 h without any significant potential reduction. As evidenced, rich N-doped rGO modified the carbon cloth,which could significantly increase the electrocatalytic active sites for OER and HER. This work provided a novel approach forsynthesizing transition bimetallic oxides grown on rich N-doped rGO-CC electrocatalysts as an innovative application of the low-cost substitution of precious metal electrocatalysts with highly efficient overall water splitting.