Increasing the Performance of Anion Exchange Membrane Water Electrolyzer Operating in Neutral pH

Anion exchange membrane water electrolysis (AEMWE) for generation of hydrogen from water is an emerging technology with high potential to surpass peer electrolyzers. However, current AEMWEs exhibit significant overpotential loss. Almost all the reported improvements in AEMWE performance have been confined to development and optimization of the conductive membranes and active electrodes to address issues regarding the ohmic and activation loss in AEMWE. However, coming from a different perspective, the strong effect of other cell components, which directly influence interfacial contact and transport phenomenon, is an important aspect to further improve the AEMWE performance and should not be neglected . Here, for the first time we report a solution to solve this missing piece of the puzzle with a highly conductive novel multifunctional liquid/gas diffusion layers (LGDLs), which consisted of well-tuned pores to asynchronously transport electrons, heat and liquid/gas while minimizing ohmic, mass transport and interfacial losses. The ohmic and mass transfer losses were reduced by 48% and 58%, respectively, thanks to the developed multifunctional LGDL and as a result the performance increased by 13 % at 0.5 A cm-2 in water, which places AEMWE close in effectiveness to more mainstream alkaline electrolyzers but without the need of using corrosive alkaline solutions as electrolyte. This multifunctional LGDL, called NiMPL-PTL, was developed by introducing nickel based micro porous layers (MPLs) using atmospheric plasma spray (APS) technique on the top of a porous transport layer (PTL) substrate. The low tortuosity of this novel porous NiMPL-PTL can reduce capillary pressure and bubble point, which can efficiently remove the unavoidable gas bubbles formed at electrode surface. Moreover, this NiMPL-PTL can decrease the contact resistance, since it increases the contact area between PTL and membrane electrode assembly (MEA) by reducing the aperture size of the PTL. Therefore, a significant mitigation of mass transport issues at high current densities and an improvement in interfacial contact resistance (ICR) were achieved by implementing NiMPL-PTL in the AEMWE operated in water. Electrochemical results showed that for AEMWE cell with well-tuned NiMPL-PTLs, the operating voltage required at the current density of 0.5 A cm-2 is as low as 1.90 V with an operating efficiency of 76%HHV, which was 290 mV lower than that of cell with the uncoated PTLs , which could only reach to efficiency of 65%HHV. To the best of our knowledge, there has been no such a genuine design of multifunctional coated backing layer PTL to improve the AEMWE performance in water.