Accelerating kinetics of oxygen evolution reaction via expanding interlayer spacing of 1D core-shell layered double hydroxides

Layered double hydroxides (LDH) have been recognized as promising electrocatalysts for OER. However, the poor electron conductivity and limited interlayer spacing that relates with the ion diffusion decrease kinetics of OER. In this work, acetate was selected to construct basic cobalt acetate (COAC) on the surface of CoNi-LDH via a facile ethanol bath reaction. The similar lamellar structure between COAC and CoNi-LDH promises the successful growth of COAC on CoNi-LDH. TEM indicates that the interlayer spacing of COAC is around 1.5 times larger than that of CoNi-LDH, accelerating the kinetics of OER via increasing ion diffusion rates. In addition, the substitution of OH with acetate changes the electron distribution of Co-O octahedron in hydroxides sheets, which was evidenced to raising the density of Co3+ in the electrocatalysts, facilitating the formation of CoOOH and promoting the intrinsic activity of nickel foam (NF) supported CoNi-LDH@COAC. Moreover, the thin and crumpled COAC layer with low crystallinity is rich of unsaturated coordination sites, increasing the density of active sites, as well as enhancing the structural stability. As a result, the overpotential of CoNi-LDH@COAC/NF (253 mV) is 45 mV and 47 mV lower than that of COAC and CoNi-LDH/NF at the current density of 10 mA cm-2 and 73 mV and 63 mV lower than that of COAC and CoNi-LDH/NF at the current density of 50 mA cm- 2, respectively. Therefore, this work unravels the enhanced catalytic mechanism of acetate anion in modulating the catalytic performance of LDH, which replenish the application of basic cobalt salt as electrocatalysts for OER.