The use and optimization of stainless steel mesh cathodes in microbial electrolysis cells (original) (raw)
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International Journal of Hydrogen Energy, 2017
While stainless steel (SS) cathodes have shown great promise due to their low cost and high specific surface areas in microbial electrolysis cells (MECs), they have mainly been examined under static (no flow) conditions. Several different SS materials with different 3dimensional structures (mesh, fiber felt, wool, and brushes) were compared in the absence and presence of fluid flow (0.05, 0.1 and 0.2 cm/s) past the cathode by catholyte recirculation. MECs with wool produced the highest hydrogen production rate with 1.3 ± 0.3 L-H 2 / L-reactor/d, which was the same as the Pt control at a catholyte recirculation of 40 mL/min (applied voltage of 0.9 V). In the absence of flow, hydrogen production rates of SS materials decreased by 52% (wool) to 28% (brush). The high hydrogen production rate using wool was likely a result of its high specific surface area (480 m 2 /m 3-reactor volume), and reduced cathode overpotential due to gas removal by catholyte recirculation.
The use of stainless steel and nickel alloys as low-cost cathodes in microbial electrolysis cells
Journal of Power Sources, 2009
Microbial electrolysis cells (MECs) are used to produce hydrogen gas from the current generated by bacteria, but low-cost alternatives are needed to typical cathode materials (carbon cloth, platinum and Nafion TM). Stainless steel A286 was superior to platinum sheet metal in terms of cathodic hydrogen recovery (61% vs. 47%), overall energy recovery (46% vs. 35%), and maximum volumetric hydrogen production rate (1.5 m 3 m −3 day −1 vs. 0.68 m 3 m −3 day −1) at an applied voltage of 0.9 V. Nickel 625 was better than other nickel alloys, but it did not perform as well as SS A625. The relative ranking of these materials in MEC tests was in agreement with cyclic voltammetry studies. Performance of the stainless steel and nickel cathodes was further increased, even at a lower applied voltage (0.6 V), by electrodepositing a nickel oxide layer onto the sheet metal (cathodic hydrogen recovery, 52%, overall energy recovery, 48%; maximum volumetric hydrogen production rate, 0.76 m 3 m −3 day −1). However, performance of the nickel oxide cathodes decreased over time due to a reduction in mechanical stability of the oxides (based on SEM-EDS analysis). These results demonstrate that non-precious metal cathodes can be used in MECs to achieve hydrogen gas production rates better than those obtained with platinum.