Liquid–solid triboelectric nanogenerators (TENGs) offer a viable approach for harvesting water energy to power Internet of Things systems. Semiconductor-based TENGs leveraging the tribovoltaic effect have recently emerged as a focus of research. In this paper, monolayer molybdenum disulfide (ML-MoS2) is introduced as a contacting material for fabricating direct current (DC) liquid–solid nanogenerators. At the internal liquid–solid interface, electron transfer is strongly evidenced by Raman and photoluminescence spectra. For the external characteristics, macroscopic DC outputs are assessed under various conditions, with a maximum current density of 11.1 mA m−2. Correlating external output patterns with interfacial charge dynamics, a complete working mechanism of the liquid–solid tribovoltaic effect is better elucidated. This work advances innovative strategies for water energy harvesting, deepening fundamental insights into liquid–solid interactions and the tribovoltaic effect.