Structured-Gradient Hydrogel Moisture Electric Generator with Milliampere and Milliwatt Level Electrical Energy Output for Smart Agriculture

Moisture-electric generator (MEG) is attractive sustainable
energy
sources, but environmental fluctuations cause unstable output, and
low power/short supply limit practical use. Here, we developed a MEG
device based on an activated carbon structured-gradient hydrogel,
which achieved milliampere and milliwatt level electrical energy output
and continuous voltage output for over 1 month. Unlike conventional
isotropic materials, this structure promotes the directional migration
of water and ions, effectively accelerating charge accumulation and
enabling continuous power generation. Concurrently, the synergistic
effect between the humidity-induced hydrogel and the slow anodic corrosion
of the aluminum electrode establishes an H+/Al3+ gradient diffusion, further improving the electrical output performance.
A single MEG device (with an area of approximately 1 cm2) can stably output a voltage exceeding 1.6 V across a wide humidity
range (20–80% RH) and a broad temperature spectrum (−40
to 60 °C), with continuous operation for over 740 h. Significantly,
the single MEG achieves 22.1 mA/cm2 current and 3.2 mW/cm2 power density, both an order of magnitude higher than previous
MEGs. Large-scale integration technology provides an effective pathway
for amplifying the electrical output performance of MEG arrays, connecting
100 MEG units in parallel yields a continuous current of ∼45
mA, with a series configuration of 120 units providing ∼192
V. The MEG array can successfully power a 5 W black light bulb and
a wireless sensing system directly, showing great potential application
in smart agriculture. This work provides a idea for advancing the
development of high-performance MEG devices and real applications.