Cellulose paper-based humidity power generator with high open circuit voltage based on zinc-air battery structure

The sensing mechanisms of common humidity sensors related to conductive active materials, which can be simply attributed to the variations in resistivity due to the separation of conductive materials and variations in polymer permittivity, are generally plagued by drawbacks such as cumbersome fabrication processes, high cost and low performance. Herein, we prepared Zn/Cellulose filter paper (CFP)/Nanoscale carbon ink (NCI)/Cu structure humidity power generators (ZHGs) based on the power generation principle of typical zinc-air batteries, using active metals with strong conductivity as electrodes, and the redox reactions that took place in the zinc-air battery can convert the chemical energy in the electrode into a stable electrical energy. The ZHG fabricated in this work can reach an extremely high open circuit voltage (V_oc) of 0.803 V at 97 % RH and possesses an excellent power density of 312.24 μW/cm², which has a good linear relationship (R² = 0.9669) over a wide humidity range (20-97 % RH). In addition, 10 ZHGs in series can charge commercial capacitors up to 3.83 V. Finally, the proof of concept demonstrated that the humidity power generation sensor can be well applied in human respiratory monitoring, finger non-contact switch, and power supply for light emitting diode (LED).