Enhanced stability of bipolar membrane water electrolysis with FeCoNi layered double hydroxides electrocatalyst in a frequently-inverted electrolyte mode

Abstract

The aim of this study was to synthesize a novel, non-noble metal-based layered double hydroxides (LDH) bifunctional catalyst for bipolar membrane water electrolysis (BPMWE) and to improve the stability of BPMWE with forward bias BPM. The FeCoNi-LDH/NF catalyst was successfully prepared using an electrodeposition method and tested in BPMWE. Low overpotentials for both the HER and OER were observed in the FeCoNi-LDH/NF electrode. Significant changes in pH and conductivity occurred in the anolyte and catholyte of BPMWE without frequently-inverted electrolyte within 192 h, resulting in an increase of cell voltage for hydrogen production. However, in the frequently-inverted electrolyte mode, where the electrolyte was periodically shifted every 24 h, excess H+ in the anolyte and OH– in the catholyte of BPMWE were effectively neutralized by electrolyte shifting, resulting in stable pH and conductivity in the electrolytes and maintaining a stable cell voltage within 192 h. With 1 M KOH as the electrolyte, the cell voltage of BPMWE was only 1.58 V under a current density of 20 mA·cm−2 at 90 °C. Our study should provide insights into efficient bifunctional catalyst synthesis and operational stability control in BPMWE.