Integrating Photoelectrochemical Feature on a Hydrovoltaic Chip with High-Salinity Adaption as a Self-Powered Device for Formaldehyde Monitoring.

Alternative energy sources are required due to the decline in fossil fuel resources. Therefore, devices that utilize hydrovoltaic technology and light energy have drawn widespread attention because they are emission-free and solar energy is inexhaustible. However, previous investigations mainly focused on accelerating the water evaporation rate at the electrode interface. Here, a cooperative photoelectrochemical effect on a hydrovoltaic chip is achieved using NH 2 -MIL-125-modified TiO 2 nanotube arrays (NTs). This device demonstrated significantly improved evaporation-triggered electricity generation. Under LED illumination, the open-circuit voltage ( V OC ) of the NH 2 -MIL-125/TiO 2 NTs active layer of the hydrovoltaic chip was enhanced by 90.3% (up to 400.2 mV). Furthermore, the prepared hydrovoltaic chip showed good high-salinity tolerance, maintaining 74.6% of its performance even in 5 M NaCl. By introducing a Schiff-based reaction between the active layer and formaldehyde, a fully integrated flexible sensor was successfully fabricated for formaldehyde monitoring, and a low limit of detection of 5.2 × 10 -9 M was achieved. This novel strategy for improving the performance of hydrovoltaic devices offers a completely new general approach to construct self-powered devices for point-of-care sensing.