(Invited) Performance and Stability of Radiation Grafted Based Anion Exchange Membrane Electrolysers
Authors: Mamlouk Mohamed , Gupta Gaurav , Scott Keith 
Published: December 2020

Hydrogen is a promising renewable fuel and energy storage solution, due to its highly efficient conversion with electricity and good energy density in comparison to most batteries. However, 95 % of the produced hydrogen globally is generated from non-renewable sources and only 5% is generated from electrolysis due to high systems cost [1,2]. Around 50% of the cost of the electrolyser system comes from the precious metal catalyst used in proton exchange membrane system [3,4]. Alkaline anion exchange membrane water electrolyser AAEM-WE allow the use of non-precious metals as: effective electro-catalyst and affordable flow fields and bipolar plates, reducing the cost significantly. It is estimated that replacement of PEM electrolysers with AAEM electrolysers could offer a 43% reduction in stack cost [5]. We look here at advantages and limitations of AAEM-WE and their ideal operating range.
Higher performances can be achieved using high alkaline feed concentration but this in turn reduces the lifetime of the system due to degradation of AEM membrane/ionomers. Thus, in order to reduce the degradation and improve the lifetime, low alkaline concentration should be used as feed solution for AEMWE i.e. deionised water. We have shown previously [4] that an electrolyser current density of 100 mA cm-2 at 1.65V using NiCo2O4 for Oxygen Evolution Reaction (OER) could be achieved at 60 °C [4]. We present here a binary-catalyst based on manganese oxides MnOx as very efficient electro-catalyst for OER with Tafel slope of 30 mV dec-1. Using low cost LDPE based membranes radiation grafted AEM, a very promising performance electrolyser was obtained of 1.59 V at 100 mA cm-2 and a current density of 1 A cm-2 at a potential of 1.78 V in 0.01 M NaOH at 60 °C. The current highest performance reported for Ni based catalysts (2.7 mg cm-2) in the AEM system is 500 mA cm-2 at a potential of 1.9 V in 1% K2CO3 solution(pH 10-11) at 60 °C [6,7] which is ca. a third of the current density reported here. This performance is comparable to PEM electrolysers performances with the reported operating voltage is in the range of 1.6-1.7 V [8] at 1 A cm-2. However, the long-term stability of these systems remains a challenge.

Keywords

: AEM, water electrolysis, alkaline, non-precious metal catalyst,

References:

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