Atomic Dispersed Ce/Ti Onto Layered Double Hydroxide Substrate Via Atomic Layer Deposition for Efficient Oxygen Evolution Reaction

Abstract

Recently, transition metal based layered double hydroxides (LDHs) based materials have attracted attention for the enhancement of oxygen evolution reaction (OER) performances due to their unique structural property, high specific capacitance, facile synthesis process and low cost. [1,2] Atomic layer deposition (ALD) is a powerful technique for realizing highly dispersed nano-species at the atomic level with a precise control over the size, shape, and composition by leveraging its self-limiting nature of surface reactions. ALD precursors could be readily combined with LDH structures due to the abundant hydroxy group on the surface of LDH structure. The additional ALD-derived doping can regulate the electronic structures of original LDH and further strength the synergetic effects between the host and doped metals for enhancing electrocatalytic activities.[3] In this study, a simple and effective method of introducing Ce as a third metal was used to prepare high-performance Ni/Co-LDH based electrodes: hydrothermal approach followed by an ALD process, using Ni foam as the substrate to achieve the growth of Ni/Co nanostructures. Smooth 2D LDH plates of a uniform structure with high surface area and abundant active sites were synthesized. The resultant CoNi-LDH@5Ce and CoNi-LDH@5Ti exhibit optimal activity and stability toward OER. In particular, CoNi-LDH@5Ce exhibits excellent OER performance with a small overpotential of 270 mV to reach 50 mA cm-2. ALD-treated samples exhibit a decreased charge transfer resistance, indicating a more efficient OER. Furthermore, both CoNi@5Ti and CoNi@5Ce show lower ohmic resistance of 1.5 Ω, which is additionally beneficial to OER performance. The enhanced performance could be attributed to a synergic effect between the doped elements (Ce, Ti) and base transitional metals (Co, Ni). Furthermore, metal oxides – especially cobalt oxide – generated on the surface during ALD process is conjectured to have contributed to an acceleration of O-O bond formation during OER process.