H₂ Evolution Catalysts for Microbial Electrolysis Cells

Microbial electrolysis cells (MECs) can efficiently produce H2 gas using organics-containing wastewater. However, traditional cathode catalysts such as platinum (Pt) are too expensive for large-scale uses. Currently, many studies have reported efficient and cheap alternatives to Pt; however, few reviews have focused on the cathode catalyst materials and their possible future development. In this chapter, we review the currently known cathode catalysts based on their performance to catalyze hydrogen evolution reaction (HER) and their material costs. The review starts by introducing mechanisms of MECs and the functions of H2 evolution catalysts, followed by presenting current types of HER catalysts and the important properties of cathode materials that affect the HER process. Greater interest is placed on the H2 production abilities and energy efficiencies of the catalysts in MECs. Moreover, the challenges and future perspectives of developing novel cathode materials have been thoroughly discussed.