Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland.
Environ Sci Technol. 2020 May 5;54(9):5746-5754. doi: 10.1021/acs.est.0c00096. Epub 2020 Apr 21.
The potential energy contained in the controlled mixing of waters with different salt concentrations (i.e., salinity gradient energy) can theoretically provide a substantial fraction of the global electrical demand. One method for generating electricity from salinity gradients is to use electrode-based reactions in electrochemical cells. Here, we examined the relationship between the electrical power densities generated from synthetic NaCl solutions and the crystal structures and morphologies of manganese oxides, which undergo redox reactions coupled to sodium ion uptake and release. Our aim was to make progress toward developing rational frameworks for selecting electrode materials used to harvest salinity gradient energy. We synthesized 12 manganese oxides having different crystal structures and particle sizes and measured the power densities they produced in a concentration flow cell fed with 0.02 and 0.5 M NaCl solutions. Power production varied considerably among the oxides, ranging from no power produced (β-MnO) to 1.18 ± 0.01 W/m (sodium manganese oxide). Power production correlated with the materials' specific capacities, suggesting that cyclic voltammetry may be a simple method to screen possible materials. The highest power densities were achieved with manganese oxides capable of intercalating sodium ions when their potentials were prepoised prior to power production.
控制不同盐浓度（即盐度梯度能）的水混合所产生的势能理论上可以提供全球电力需求的很大一部分。从盐度梯度中发电的一种方法是在电化学电池中使用基于电极的反应。在这里，我们研究了从合成 NaCl 溶液中产生的电功率密度与锰氧化物的晶体结构和形态之间的关系，锰氧化物的氧化还原反应与钠离子的吸收和释放有关。我们的目标是朝着开发用于收获盐度梯度能的电极材料的合理框架取得进展。我们合成了 12 种具有不同晶体结构和粒径的锰氧化物，并在浓度流动池中测量了它们在 0.02 和 0.5 M NaCl 溶液中的功率密度。氧化物之间的发电差异很大，从不发电（β-MnO）到 1.18 ± 0.01 W/m（钠锰氧化物）。发电与材料的比容量有关，这表明循环伏安法可能是筛选可能材料的一种简单方法。在发电之前对电势进行预偏置，能够嵌入钠离子的锰氧化物可以实现最高的功率密度。
