Construction of porous flower-like Ru-doped CoNiFe layered double hydroxide for supercapacitors and oxygen evolution reaction catalysts

Abstract

In recent years, ternary layered double hydroxide (LDH) has become a research hotspot for electrode materials and oxygen evolution reaction (OER) catalyst due to the enhanced synergistic effect between individual elements. However, the application of LDH is greatly limited by its low electrical conductivity and the disadvantage that nanosheets tend to accumulate and mask the active sites. Herein, a novel Ru-doped CoNiFe − LDH was prepared via a facile hydrothermal method. According to the density functional theory (DFT) calculations, the doping of Ru element could improve electron state density and band gaps of LDH and consequently boosted the electrochemical reaction kinetics as well as electrical conductivity. Furthermore, introduction of Ru atom induced the formation of porous flower-like structures in nanosheets. Compared to CoNiFe − LDH (28.9 m2/g), Ru-doped CoNiFe − LDH performed larger specific surface area of 53.1 m2/g, resulting in more electrochemically active sites. In these case, Ru-doped CoNiFe − LDH demonstrated better energy storage performance of 176.0 mAh/g at 1 A/g compared to original CoNiFe − LDH (78.9 mAh/g at 1 A/g). Besides, the assembled Ru-doped CoNiFe − LDH//activated carbon (AC) device delivered a maximum energy density of 36.4 W h kg−1 at the power density of 740.3 W kg−1 and an outstanding cycle life (78.7 % after 10,000 cycles). Meanwhile, Ru-doped CoNiFe − LDH exhibited lower overpotential (339 mV at 50 mA cm−2) and Tafel slope (93.2 mV dec−1). Therefore, this work provided novel and valuable insights into the rational doping of Ru elements for the controlled synthesis of supercapacitor electrode materials and OER catalysts.