Electrodeposition Fabrication of La-Doped NiFe Layered Double Hydroxide to Improve Conductivity for Efficient Overall Water Splitting

Abstract

The electrolysis of water requires excess energy in the form of overpotential to overcome activation barriers due to the sluggish kinetics of both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As an inexpensive bifunctional catalyst with noble-metal-like electrocatalytic properties, twodimensional layered double hydroxides (LDHs) have received considerable attention. Here, a simple electrodeposition method is proposed to synthesize a La-doped NiFe LDH (NiFeLa LDH) on a nickel foam. NiFeLa LDH exhibits excellent water splitting performance due to the synergistic effect of La and laminate metal, with the best overpotential of 399 mV for OER and 223 mV for HER at a current density of 50 mA cm −2 , along with excellent durability in alkaline solution tests for 24 h. The electrochemical performance analysis and other characterization results confirm that La doping can change the electronic structure of LDH laminates. According to density functional theory calculations, the remarkably enhanced catalytic performance of NiFeLa LDH is ascribed to the decrease in the activation energy of adsorbed oxygen due to the adsorption of hydroxide, making the transformation from *OH to *O the rate-determining step of the OER process with a four-electron mechanism. Additionally, the electrolyzer with NiFeLa LDH as both anode and cathode provides good stability as well as a reduced cell voltage of 1.921 V to provide a current density of 50 mA cm −2 . Overall, this study offers a simple, convenient, rapid, and environmentally friendly method for fabricating high-performance water splitting catalysts.