Study on monolayer NiFe layered double hydroxide as oxygen evolution reaction electrocatalysts applicable to alkaline anion exchange membrane water electrolysis

Abstract

Among many oxygen evolution reaction catalyst candidates, NiFe layered double hydroxide (LDH) show the highest activity in alkaline medium. Unfortunately, NiFe-LDH is known to have poor electrical conductivity due to the spacings between the cationic layers, limiting its potential as an electrocatalyst. In order to improve electrical conductivity, many researches utilized carbonaceous material as support or substrate for NiFe-LDH. However, our findings point out that use of carbonaceous materials for anode can have detrimental effects on the stability of AEMWE. Instead, a facile monolayer structuring of NiFe-LDH is suggested as a strategy to overcome low conductivity of NiFe-LDH without use of carbonaceous materials. The synthesized monolayer NiFe-LDH showed higher overall water splitting performance compared to conventional bulk NiFe-LDH, achieving high energy conversion efficiency of 72.6% without carbonaceous material and an outstanding stability at current density of 1 A cm$^{-2}$ at 50°C and 80°C with 1 M KOH as electrolyte. This efficiency is one of the highest among AEMWE, suggesting monolayer structuring as an effective way to improve activity and stability at industrially relevant values.