Natural water evaporation (NWE) can be used as a driving force to generate electricity. NWE-driven generators (NWEGs) require materials with charged surfaces. However, the quantitative adjustment of the surface charge density (d_c) remains difficult and the relationship between d_c and NWEG performance has not been clarified. Herein, Ni-Al layered double hydroxide (LDH) films with tailored structural d_c in the range of 2.52–4.59 e/nm² were synthesized by precisely adjusting the molar ratio of Al³⁺ to Ni²⁺. The Ni-Al LDH films were assembled into NWEGs by the spraying method and then their electrical performance was investigated. Strong positive correlations were observed between d_c, open-circuit voltage (V_oc), and short-circuit current (I_sc); that is, the larger d_c, the higher V_oc and I_sc. The maximum V_oc of ∼0.6 V, I_sc of ∼0.3 μA, and output power density of ∼15 μW/cm³ were achieved simultaneously for a 4 × 1.5 cm NWEG with a maximum d_c of 4.59 e/nm². A reasonable increase of d_c resulted in improved device performance, which was attributed to the positive correlation between the densities of both hydroxide ions in the diffusion layer and positive charge on the Ni-Al LDH film surface. In addition, a relatively stable total V_oc of ∼2.5 V and I_sc of ∼1.5 μA were obtained using eight NWEGs with a modified individual generator structure. The eight assembled NWEGs successfully powered a simple electronic watch. The spraying method used to fabricate the NWEGs not only greatly shortened the device molding time, but also markedly improved device stability. This study reveals a new avenue to guide the design of materials and to improve the performance of flexible self-powered NWEGs.

天然水蒸发（NWE）可用作驱动力来发电。NWE驱动的发电机（NWEG）要求表面带电的材料。然而，表面电荷密度（d _c）的定量调节仍然很困难，并且d _c与NWEG性能之间的关系尚未阐明。在此，通过精确调节Al ³⁺与Ni ²⁺的摩尔比，合成了结构度d _c在2.52-4.59 e / nm ²范围内的Ni-Al层状双氢氧化物（LDH）薄膜。。通过喷涂法将Ni-Al LDH薄膜组装成NWEG，然后研究其电性能。在d _c，开路电压（V _oc）和短路电流（I _sc）之间观察到很强的正相关。即，d _c越大，V _oc和I _sc越高。对于4×1.5 cm NWEG，最大d _c为4.59 e / nm ^2，同时获得了约0.6 V的最大V _oc，约0.3μA的I _sc和约15μW/ cm ^3的输出功率密度。。d _c的合理增加导致器件性能提高，这归因于扩散层中两个氢氧根离子的密度与Ni-Al LDH膜表面上的正电荷之间的正相关。此外，相对稳定的总V _oc为〜2.5 V，I _sc使用八个具有改进的独立发生器结构的NWEG，可获得约1.5μA的电流。八个组装好的NWEG成功为一个简单的电子表供电。用于制造NWEG的喷涂方法不仅大大缩短了器件的成型时间，而且显着提高了器件的稳定性。这项研究揭示了一条指导材料设计和提高柔性自供电NWEG性能的新途径。