Fabrication of NiO Microflake@NiFe-LDH Nanosheet Heterostructure Electrocatalysts for Oxygen Evolution Reaction

The development of highly efficient eletrocatalysts for water electrolysis application is a rising hot issue; especially the oxygen evolution reaction (OER) attracted wide attention due to the significant overpential derived by the complex four electron-transfer coupled reaction. In this study, hierarchical NiO microflake@NiFe-layer double hydroxide (LDH) nanosheet core shell arrays on nickel foam were fabricated by combining a two-step hydrothermal synthesis and a calcination process. Due to the three-dimensional rational configuration, the obtained composite electrode showed high performance for OER, which needed a low apparent over potential of 265 mV to afford a 10 mA cm(-2) current density. In addition, the NiO@NiFe-LDH coated electrode was further treated in an organic solution via ultrasound for in situ intercalation of the NiFe-LDH to provide wide channels for ion transportation and gas diffusion. As a result, the charge transition resistance was obviously reduced and the apparent activity as well as the long-term stability was improved. The optimized NiO@NiFe-LDH composite exhibited an excellent long-term stability in 50 h even at high current densities of 50 and 100 mA cm(-2), and meanwhile the required apparent overpotential of OER for sustaining 10 mA cm(-2) current density was reduced from 265 to 210 mV.