Grey relational analysis for comparative assessment of different cathode materials in microbial electrolysis cells

MEC (Microbial electrolysis cell) is an emerging and promising bio-electrochemical process for sustainable production of hydrogen gas. The performance and cost of cathode materials are the most important factors in MEC. In order to enhance MEC performance and reduce the fabrication and operational costs of electrodes, a wide range of cathode materials have been developed and tested in the recent years. However, no standard and systematic analytical method has been developed to make a comparative assessment of the cathode materials in MECs. In this study, a statistical method, namely GRA (grey relational analysis) was exploited to evaluate hydrogen evolution performance of eight different non-precious metal alloy cathodes, including stainless steel alloys 304, 316, 420, A286, and nickel alloys 201, 400, 625 with Ni HX in comparison to precious metal of Pt (platinum). Statistical results revealed that materials tested were ranked based on the grey relational grade values as ASS 286 > Pt > SS 304 > Ni 625 > SS 420 > Ni HX > Ni 400 > Ni 201 > SS 316. The results obtained showed stainless steel A286 had the best efficiency in MEC test based on grey relational grade. This study indicated that GRA could be used as a novel method to assess the performance of cathodes in MEC.