Chinese Journal of Chemical Engineering ›› 2021, Vol. 29 ›› Issue (3): 33-41.doi: 10.1016/j.cjche.2020.09.041

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Understanding electrokinetic thermodynamics in nanochannels

Jianglong Du1, Haolan Tao1, Jie Yang1, Cheng Lian1,2, Sen Lin3, Honglai Liu1   

  1. 1 State Key Laboratory of Chemical Engineering, Shanghai Engineering Research Center of Hierarchical Nanomaterials, and School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China;
    2 Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, the Netherlands;
    3 National Engineering Research Center for Integrated Utilization of Salt Lake Resources, and State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237, China
  • Received:2020-08-21 Revised:2020-09-25 Online:2021-03-28 Published:2021-05-13
  • Contact: Cheng Lian, Sen Lin, Honglai Liu;;
  • Supported by:
    This work was sponsored by the National Natural Science Foundation of China (No. 91834301, 21808055 and 22078088), the Shanghai Sailing Program (18YF1405400).

Abstract: Understanding the electrokinetic conversion efficiency in a nanochannel is vital for designing energy storage and conversion devices. In this paper, an analytical electrokinetic energy conversion efficiency in a nanochannel is obtained based on the linear electrokinetic response. The analytical result shows that the conversion efficiency has a maximum with the increasing of the nanochannel pore radius. Numerical solutions based on the Poisson-Nernst-Planck (PNP) and Navier-Stokes (NS) equations are used to confirm the analytical expressions. Besides, the influences of the pore radius and surface roughness on the conversion efficiency in nanochannels are also studied by the numerical calculations. In particular, the influences of the surface roughness on the fluid flow, streaming current and streaming potential are examined. The results show that the large bumps and grooves representing the roughness can hinder the fluid flows and ion transports in the nanochannels. The maximum efficiency in a smooth nanochannel is higher than that in a rough channel. However, the small bumps and grooves can increase the surface area of the channel, which is beneficial to improving the conversion efficiency in some cases. This research can provide theoretical guidance to design electrokinetic energy conversion devices.

Key words: Electrokinetic conversion efficiency, Linear electrokinetics, Nanostructure, Dynamic simulation, Thermodynamics