Enhanced hydrogen production in microbial electrolysis cell with 3D self-assembly nickel foam-graphene cathode

In comparison to precious metal catalyst especially Platinum (Pt), nickel foam (NF) owned cheap cost and unique three-dimensional (3D) structure, however, it was scarcely applied as cathode material in microbial electrolysis cell (MEC) as the intrinsic laggard electrochemical activity for hydrogen recovery. In this study, a self-assembly 3D nickel foam-graphene (NF-G) cathode was fabricated by facile hydrothermal approach for hydrogen evolution in MECs. Electrochemical analysis (linear scan voltammetry and electrochemical impedance spectroscopy) revealed the improved electrochemical activity and effective mass diffusion after coating with graphene. NF-G as cathode in MEC showed a significant enhancement in hydrogen production rate compared with nickel foam at a variety of biases. Noticeably, NF-G showed a comparable averaged hydrogen production rate (1.31±0.07mL H₂mL^-1 reactord^-1) to Platinum/carbon (Pt/C) (1.32±0.07mL H₂mL^-1 reactord^-1) at 0.8V. Profitable energy recovery could be achieved by NF-G cathode at higher applied voltage, which performed the best hydrogen yield of 3.27±0.16mol H₂mol^-1 acetate at 0.8V and highest energy efficiency of 185.92±6.48% at 0.6V.