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The coexistence of an evaporation potential and streaming potential in a NWEG has been proposed using ZSM-5 as the generation material. A streaming potential formed as water flowed inside the ZSM-5 nanochannels, driven by electrodynamic effects that increased from the bottom to the top of the generator. Conversely, an evaporation potential existed at the surface-gas interface of the ZSM-5-solution, which decreased from the bottom to the top as the evaporation height increased. The resulting open-circuit voltage (V oc) depended on the balance between evaporation and streaming potential, both of which were influenced by the evaporation enthalpy (E e) or vapor pressure. Generally, a higher E e or lower vapor pressure led to a lower evaporation potential and subsequently a lower V oc. A dual mechanism involving synergistic evaporation potential and streaming potential is proposed to explain the mechanism of NWEGs. [Display omitted] Electricity generation by natural water evaporation generators (NWEGs) using porous materials shows great potential for energy harvesting, but mechanistic investigations of NWEGs have mostly been limited to streaming potential studies. In this study, we propose the coexistence of an evaporation potential and streaming potential in a NWEG using ZSM-5 as the generation material. The iron probe method, salt concentration regulation, solution regulation, and side evaporation area regulation were used to analyze the NWEG mechanism. Our findings revealed that a streaming potential formed as water flowed inside the ZSM-5 nanochannels, driven by electrodynamic effects that increased from the bottom to the top of the generator. In addition, an evaporation potential existed at the surface interface between ZSM-5 and water, which decreased from the bottom to the top as the evaporation height of the generator increased. The resulting open-circuit voltage (V oc) depended on the balance between the evaporation and streaming potentials, both of which were influenced by the evaporation enthalpy (E e) or vapor pressure. Generally, a higher E e or lower vapor pressure led to a lower evaporation potential and subsequently a lower V oc. A dual mechanism involving synergistic evaporation potential and streaming potential is proposed to explain the mechanism of NWEGs. [ABSTRACT FROM AUTHOR]

Charge dynamics play essential role in many practical applications such as semiconductors, electrochemical devices and transmembrane ion channels. A Maxwell-Ampère Nernst-Planck (MANP) model that describes charge dynamics via concentrations and the electric displacement is able to take effects beyond mean-field approximations into account. To obtain physically faithful numerical solutions, we develop a structure-preserving numerical method for the MANP model whose solution has several physical properties of importance. By the Slotboom transform with entropic-mean approximations, a positivity preserving scheme with Scharfetter-Gummel fluxes is derived for the generalized Nernst-Planck equations. To deal with the curl-free constraint, the dielectric displacement from the Maxwell-Ampère equation is further updated with a local relaxation algorithm of linear computational complexity. We prove that the proposed numerical method unconditionally preserves the mass conservation and the solution positivity at the discrete level, and satisfies the discrete energy dissipation law with a time-step restriction. Numerical experiments verify that our numerical method has expected accuracy and structure-preserving properties. Applications to ion transport with large convection, arising from boundary-layer electric field and Born solvation interactions, further demonstrate that the MANP formulation with the proposed numerical scheme has attractive performance and can effectively describe charge dynamics with large convection of high numerical cell Péclet numbers. • A structure-preserving numerical scheme for MANP model with correlations. • Numerical scheme based on Slotboom transform with entropic mean approximation. • Numerical analysis on structure-preserving properties at discrete level. • A convergent, linear and local relaxation algorithm to realize curl-free. • Robust simulations of ion transport with large convection. [ABSTRACT FROM AUTHOR]