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
Kai Zhang, Pingping Jiang, Qian Gu, Yan Leng, Pingbo Zhang
Abstract
The rapid development of high-efficiency and low-price bifunctional electrocatalysts for replacing precious metal catalysts has been confronted with an enormous challenge for the oxygen 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 reduced graphene oxide (NiFe2O4@N-rGO-CC) was synthesized through the two-step hydrothermal reaction. The experimental integrity test revealed that NiFe2O4@N-rGO-CC exhibited excellent electrocatalytic performance and long-term stability in both alkaline and acid electrolytes. In a 1.0 M potassium hydroxide (KOH) solution, lower overpotentials of 479 and 156 mV were acquired to deliver the current density of 10 mA·cm–2 for both OER and HER, respectively. Besides, NiFe2O4@N-rGO-CC also exhibited excellent HER performance in 0.5 M H2SO4 solution, which provided a lower overpotential of 188 mV with a current density of 10 mA·cm–2. NiFe2O4@N-rGO-CC showed extremely stable durability over a 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 mA·cm–2 for alkaline water splitting, and it could be maintained 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 for synthesizing 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.