Nanochannel-dependent power generation performance of NiAl-LDH/SiO2-based generators driven by natural water evaporation

Abstract

Natural water evaporation is a green method to generate electrical energy. However, correlations between nanochannels constructed from generation materials and output electrical performances are unclear. In this paper, NiAl layered double hydroxide/SiO₂ (NiAl-LDH/SiO₂-x nm) composites as power generation materials with tunable nanochannels are designed using NiAl-LDH as the template and SiO₂ as the coated layer. The nanochannel size is tunable in a certain range by the SiO₂ coated thickness (x nm) on the surface of the NiAl-LDH. When the coated thickness of SiO₂ increases across the series of 0, 4, 9, and 14 nm, the nanochannel sizes built from NiAl-LDH/SiO₂-x nm (x = 0, 4, 9, 14) are 3.524, 3.186, 2.397, and 3.674 nm, respectively. The open-circuit voltage (V_oc) of the natural water evaporation generator (NWEG) exhibits an opposite trend compared to the nanochannel sizes of generation materials. When a nanochannel of 2.397 nm is constructed using NiAl-LDH/SiO₂-9 nm, the NWEG exhibits a maximum V_oc of 1.40 V, current density of 356 μA m⁻², and power density of 0.498 mW m⁻². This work reveals that a smaller nanochannel increases the concentration of counter ions and decreases fluid drag from electrical double layer (EDL) overlapping, which results in a higher electric potential.