High-performance anion-exchange membrane water electrolysers using NiX (X = Fe,Co,Mn) catalyst-coated membranes with redox-active Ni–O ligands

Abstract

Recent efforts in anion-exchange membrane water electrolysis (AEMWE) focus on developing superior catalysts and membrane electrode assemblies to narrow the performance gaps compared with proton-exchange membrane water electrolysis (PEMWE). Here we present and characterize Ir-free AEMWE cells with NiX (X = Fe, Co or Mn) layered double hydroxide (LDH) catalyst-coated membranes with polarization characteristics and hydrogen productivities approaching those of acidic PEMWE cells, achieving >5 A cm−2 at <2.2 V. Operando spectroscopy revealed a correlation between Ni4+ centres and redox-active O ligands with an O K-edge feature, attributed to µ3-O ligands in the γ-LDH catalytic phase via density functional theory calculations. This computational–experimental study challenges the previously assumed correlation between spectral O K-edge features and oxygen evolution reaction performance in Ni-based LDH catalysts and provides insights from the molecular to the technological level demonstrating how redox-active Ni–O species and innovative catalyst-coated membrane preparation boost AEMWE performance to values rivalling state-of-the-art PEMWE cell technology. Anion-exchange membrane water electrolysers have the potential to rival more costly acidic proton-exchange membrane electrolysers, but their performance and efficiency commonly still fall short. Now an anion-exchange membrane water electrolyser is prepared with a NiFe layered double hydroxide catalyst-coated membrane that achieves high current densities above 2 A cm−2 at 1.8 V and operando X-ray absorption spectroscopy is used to track the formation of the catalytically active γ-LDH phase.