Fast microwave-assisted preparation of nickel–copper–chromium-layered double hydroxide as an excellent electrocatalyst for water oxidation

Abstract

Herein, we describe a simple microwave method for the doping of Cu²⁺ into NiCr-LDH and the preparation of ternary Ni_2.25Cu_0.75Cr-LDH as a superior electrocatalyst for water oxidation in a neutral solution. The obtained Ni_2.25Cu_0.75Cr-LDH was characterized by XRD, DRS, TEM and FE-SEM techniques. The results showed that Ni_2.25Cu_0.75Cr-LDH was formed with a size of 30 nm. In order to examine the water oxidation activity of Ni_2.25Cu_0.75Cr-LDH, the as-prepared samples were used as an electrocatalyst-modified carbon paste electrode in neutral solution. The electrochemical results revealed that the optimized Ni_2.25Cu_0.75Cr-LDH presented extraordinary water oxidation activity with a low onset potential of 1.40 V (vs. RHE) and an overpotential of 170 mV compared to other molar ratios (Ni_2.5Cu_{0. 5}Cr-LDH), (Ni₂CuCr-LDH), and bimetallic (CuCr-LDH), and even outperformed NiCr-LDH. Also, a small Tafel slope of 31 mV and high durability of 14 h could be obtained for Ni_2.25Cu_0.75Cr-LDH. The excellent OER could be assigned to the decreased band gap energy and increased charge transfer at Ni_2.25Cu_0.75Cr-LDH. Therefore, Ni_2.25Cu_0.75Cr-LDH is a promising water oxidation catalyst owing to its improved charge transfer ability.