Semester of Graduation

Spring 2019

Degree

Master of Civil Engineering (MCE)

Department

Department of Civil and Environmental Engineering

Document Type

Thesis

Abstract

The globally extractable salinity gradient (SG) energy from the mixing of seawater and river water is estimated to be 3% of worldwide electricity consumption. Here we applied carbonized peat moss (CPM) electrodes and molybdenum disulfide (MoS2) electrodes to a concentration flow cell that is capable of harvesting SG energy based on the electrode (pseudo-)capacitance together with the Donnan potential. The CPM electrodes were made from the visually inexhaustible peat moss by a facile pyrolysis process. With two identical CPM electrodes and a cation-exchange membrane, the cell produced a peak power density of 5.33 W m-2 and an average power density of 950 mW m-2, the highest ever reported for CDLE-based techniques, using synthetic seawater (30 g L-1 NaCl) and river water (1 g L-1 NaCl). The cells with MoS2 electrodes and an anion-exchange membrane, although produced slightly lower power density with a peak power density of 5.21 W/m2 and an average power density of 0.76 W/m2, harvested more energy during each cycle with an energy density of 66.59 J/m2. The excellent performance of the concentration flow cells was a result of the superior properties of the electrode materials (the macroporous structure of CPM electrodes and the significantly expanded interlayer spacing of MoS2), the assistance of Donnan potential, and the double-channel structure of the cell. Both electrodes were durable as they could extract energy from highly saline water (300 g L-1 NaCl) and still worked well after 100 cycles. This study provides a new method to efficiently and continuously harvest SG energy without an external charge.

Committee Chair

Zhu, Xiuping

DOI

10.31390/gradschool_theses.4877

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