None-platinum electrode catalysts and membranes for highly efficient and inexpensive H2 production in microbial electrolysis cells (MECs): A review

Microbial electrolysis cell (MEC) is a gripping bio-electrochemical device producing H2 gas from renewable biomass while at the same time treat wastewater.  Through extensive global research efforts in the latest decade, the performance of MECs, including energy efficiency, hydrogen production rate (HPR), and hydrogen recovery have achieved significant breakthroughs. However, employing a low-cost, stable and high efficient cathode to replace platinum catalyzed cathode (Pt/C) is the greatest challenge for large-scale industrialization of MEC. Numerous studies have demonstrated that the performance of MEC directly depends on the kinetics of the anode and cathode reactions within the electrolysis cell, with the performance of the electrode catalyst highly affected by the materials they are made from. In a relatively short space of time, a wide range of electrode materials have been tested to amplify the performance of MECs, such as carbon-based electrode catalysts have emerged as promising electrode materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electro-catalyst manufacture. More recently, various transition metal oxides and alloys have been extensively examined as alternatives to conventional expensive noble-metals like platinum for hydrogen evaluation reaction (HER) in MECs. Numerous studies have confirmed that stainless steel, Ni alloys, and Pd nanoparticle decorated cathode are worth mentioning and have very good efficiency. In the present article, we present a comprehensive review centered on the development of a low-cost and high efficient electrode materials and membrane to boost the performance of MECs, including anode, cathode, and membrane.