Scalable Synthesis of Highly Efficient Nife-Layered Double Hydroxides as Electrocatalyst for Water Oxidation

Abstract

Oxygen evolution reaction (OER) is reckoned as the limiting step for water splitting, suffering slow kinetics (>10 000 lower than the hydrogen evolution reaction), and therefore requiring high overpotentials. Nowadays, there is a huge effort in the development of low-cost, earth-abundant, efficient, and stable electrocatalysts. Layered double hydroxides (LDHs) based on NiFe fulfil these requirements, and in addition, it possesses one of the best performances for oxygen evolution reaction (OER) in basic media reported to date.[1] LDHs exhibit a hydrotalcite-like structure composed of M(II) and M(III) cations and depict wide tunability regarding the metallic composition. However, despite their great performance, the implementation of Fe-based LDHs as electrocatalysts in real devices remains unexplored, mainly due to the current challenging synthetic approaches, incompatible with their scaling.[2] Herein we present a high clustering nanometric NiFe-LDHs obtained by a scalable synthesis. The synthetic protocol gets the opportunity to obtain ca. 100 g/L of our materials, almost two orders of magnitude bigger than the state-of-the-art synthetic approaches. Moreover, the intrinsical characteristics of this scale-up NiFe-LDH confer a better electrochemical performance than traditional synthesized NiFe-LDH in all current density ranges and different electrochemical setups from rotatory disk electrode (RDE) to Anion Exchange Membrane Water Electrolyzer (AEMWE), being tested up to a current density of 3 A·cm-2. For example the overpotential at 2.5 A·cm-2 for the scale up NiFe-LDH and Traditional synthesized NiFe-LDH samples are 1.96 V and 2.18 V, respectively (Figure 1). Interestingly, this behavior is in contrast to the recent result warning about the possibility of cell environments matching the cell performance of design catalysts.[3]