A Self-Powered pH Sensing Method Based on a Triboelectric Nanogenerator: An Innovative Application in Marine Ranch Water Quality Monitoring

To achieve intelligent aquaculture and ensure environmental health, water quality monitoring is indispensable in marine ranching. However, the energy supply for widely deployed sensors remains a critical challenge. Self-powered sensing technology is one of the core solutions to address this bottleneck. In this research, a capsule-structured, solid–solid/solid–liquid mixed-mode triboelectric nanogenerator (TENG) is proposed, which addresses the limitations of the existing TENG technology in marine environments. The proposed TENG collects wind and wave energy by coupling solid–solid contact electrification with the bilayer effect at the solid–liquid interface under complex marine conditions. A theoretical model of triboelectric energy conversion and solid–liquid pH sensing is developed. Additionally, the TENG self-powered sensing structure is optimized to improve its performance for pH monitoring under a range of conditions in marine ranches. The experimental results demonstrate that the capsule-type dual-mode TENG (CD-TENG) achieves an open-circuit voltage of 50 V and a short-circuit current of 25 μA under optimal conditions. The peak power density of 0.35 W/m² enables sustained operation of low-power microelectronics, which is beneficial for real-time water quality monitoring in marine ranching.