Solar-driven hydrovoltaic-pyroelectric hybrid generator for efficiently harvesting water transformation energy

Manipulation of water for power generation has garnered significant research interest as it is renewable, sustainable, and a spontaneous form of energy production. However, energy conversion efficiency has remained constrained, primarily attributed to the slow evaporation rates of water and limited energy recovery strategies. Herein, we demonstrate a two-pronged hybrid water transformation energy harvester that strategically integrates solar-thermal effects with pyroelectric effects to boost water transformation and its associated energy extraction. The core of our unique ensemble consists of two layers: the upper layer features a composite film comprising carbon black (CB) and polyvinylidene fluoride (PVDF) coated onto bamboo fibers (CB/PVDF@BFP), which realizes solar-thermal and hydrovoltaic effects owing to the excellent solar-thermal and electrical activities of CB while the bottom layer is PVDF film to simultaneously generate pyroelectricity. Notably, the optimized CB/PVDF@BFP achieves a maximal temperature of ∼78 ℃ and an open-circuit voltage (VOC) and a short-circuit current (ISC) of 0.33 V and 1.6 μA, respectively. Consequently, we achieved a maximal output power density of 64 μW/m2 under one sun (25 ℃), surpassing the output under dark conditions by ∼92 %, and exceeding most similar designs. Moreover, the CB/PVDF@BFP film exhibits a maximal oscillation of ∼0.5 ℃/s and an evaporation rate of 1.44 kg·m−2·h−1 under optimized conditions, owing to the strategic inclusion of hydrophilic BFP. Concurrently, our ensemble also generates a maximum VOC, ISC and output power density of pyroelectricity of ∼80 V, 0.4 μA, and 7.4 mW/m2 (∼25.9-fold higher than the dark state), which is > ∼3.9-time higher than the similar reports, respectively. As proof of concept, our hybrid design can successfully power various household electronic devices (such as LED lights, electronic watches etc.) by storing the harvested energy into capacitors, thus showcasing its potential for practical applications. Our ensemble not only demonstrates remarkable performance but also lays the foundation for innovative concepts in the development of emerging hybrid micro/nano-generators, offering an avenue for harnessing ubiquitous ambient energy.