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Recycling Urine for Hydrogen Production in a Microbial Electrolysis Cell (MEC) System using a Novel MoS2 Nano carbon Coated Electrode
Citation:
Lee, W., J. Hwang, S. Fahad, H. Ryu, K. Rodriguez, J. SantoDomingo, AND A. Kushima. Recycling Urine for Hydrogen Production in a Microbial Electrolysis Cell (MEC) System using a Novel MoS2 Nano carbon Coated Electrode. Presented at 11th International Conference on Environmental Pollution and Remediation (ICEPR'21), NA, August 05 - 07, 2021.
Impact/Purpose:
With regards to water-energy nexus technology in wastewater, urine has great potential to be a future sustainable energy source for water, oxygen or hydrogen generation. Microbial electrolysis cells (MECs) have attracted increasing attention due to their sustainable treatment approach using wastewater as an alternative energy source. While MECs using municipal wastewater have been widely studied, only a few studies have been reported for the recovery of nutrients from urine, but capital costs such as electrodes for water electrolyzers need to be reduced. It is shown here that a novel MoS2-nano carbon (NC) electrode for generating hydrogen in a MEC, while treating urine. MoS2-NC electrode provide a low cost, but durability similar to platinum and other nanomaterials. These results show that by using a MoS2-NC electrode, the costs of electrode catalysts can be reduced, and thus provide scale up MECs development for improving of water-energy nexus.
Description:
Microbial electrolysis cells (MECs) can produce hydrogen gas from organic compounds in an energy-efficient way by taking advantage of the potential generated by microorganisms. Human urine has been successfully used as an electrolyte and organic substrate in bioelectrochemical systems (BESs) mainly due of its unique properties such as high conductivity in a solution which can reduce the ohmic losses and improve BES output. However, the hydrogen evolution reaction (HER) in MECs using urine is a slow process and thus requires the development of catalysts in a cathode. In this study, a novel molybdenum disulfide (MoS2) nano-carbon (NC) coated cathode was developed for urine treatment and improved hydrogen production in a microbial electrolysis cell (MEC) with different experiments ranging from 2-6 times diluted urine. MoS2 nanoparticles were electrodeposited on the NC coated cathodes with -100, -150 and -200 µA cm-2 and their performance was compared to NC only and carbon cloth (CC) cathodes in the MEC. The MoS2-NC200 (electrodeposition at -200 µA cm-2) cathode produced slightly higher hydrogen rates (0.061 ± 0.004 m3 H2 m-3 MEC d-1) compared to MoS2-NC100 (0.058 ± 0.002 m3 H2 m-3 MEC d-1) under two times diluted urine. The MoS2-NC200 cathode had significantly higher (~31%) hydrogen production than the carbon cloth (CC) cathode with the same dilution of urine. The reproducibility tests of the MoS2-NC cathodes after a short MEC operation period (~ 5 cycles) showed a stable MoS2 coating on the NC cathodes. Maximum ammonia-nitrogen (NH3-N) and phosphorus (PO43--P) removal with varying dilution factors was 68.7 ± 0.1% and 98.6 ± 0.3%, respectively. Some of the exoelectrogenic bacteria were identified as members of the Clostridia and Bacteroidetes taxa. The newly fabricated MoS2-NC cathode will be a suitable strategy for microbial acclimation to urine in a MEC for a novel biotransformation process within the water-energy nexus.