Hu Xiaoyu, Nan Yiling, Kong Xian, Lu Diannan, Wu Jianzhong
Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.
Phys Chem Chem Phys. 2020 Apr 29;22(16):9110-9116. doi: 10.1039/d0cp00997k.
The traditional methods to predict electrokinetic energy conversion (EKEC) in nanochannels are mostly based on the Navier-Stokes (NS) equation for ionic flow and the Poisson-Boltzmann (PB) equation for charge distributions, which is questionable for ion transport through highly charged nanochannels. In this work, the classical density functional theory (cDFT) is used together with molecular dynamics (MD) simulation and the Navier-Stokes (NS) equation to predict the electrical current and the thermodynamic efficiency of electrokinetic energy conversion in nanochannels. By introducing numerical results for the slip length calculated from MD simulation, a significant increase of the electrokinetic current is predicted in comparison to that obtained from the traditional electrokinetic equations with the non-slip boundary condition, leading to the theoretical predictions of the thermodynamic efficiency for electrokinetic energy conversion in nanochannels in good agreement with recent experiments. The hybrid method predicts that maximum electrokinetic efficiency can be achieved by tuning the channel height and solution conditions including electrolyte concentrations, ion valences, and surface energies. The theoretical results provide new insights into pressure-driven electrical energy generation processes and helpful guidelines for engineering design and optimization of electrokinetic energy conversion.
预测纳米通道中动电能量转换（EKEC）的传统方法大多基于用于离子流的纳维-斯托克斯（NS）方程和用于电荷分布的泊松-玻尔兹曼（PB）方程，然而对于离子通过高电荷纳米通道的传输而言，这些方程存在问题。在这项工作中，经典密度泛函理论（cDFT）与分子动力学（MD）模拟以及纳维-斯托克斯（NS）方程一起用于预测纳米通道中动电能量转换的电流和热力学效率。通过引入由MD模拟计算得到的滑移长度的数值结果，与采用无滑移边界条件的传统动电方程相比，预测的动电流显著增加，从而使得纳米通道中动电能量转换的热力学效率的理论预测与近期实验结果高度吻合。该混合方法预测，通过调整通道高度以及包括电解质浓度、离子价态和表面能在内的溶液条件，可以实现最大动电效率。理论结果为压力驱动的电能产生过程提供了新的见解，并为动电能量转换的工程设计和优化提供了有益的指导。
