Hydrovoltaic-photovoltaic electricity generators based on cyanobacterial biofilms

<p indent="0mm">Simultaneously harnessing environmental moisture and solar energy for continuous, all-weather electricity generation represents a critical strategy to address energy shortages. However, significant challenges persist. Current studies predominantly rely on complex self-assembly processes to fabricate composite functional materials, leading to high costs and suboptimal energy conversion efficiencies. <italic>Synechocystis</italic> sp. PCC 6803, a naturally occurring cyanobacterium, is used extensively in photovoltaic energy research and offers much potential for multienergy coupling for power generation. Inspired by the photosynthetic mechanisms of algae, which simultaneously capture moisture and solar energy, this study presents a novel hydrovoltaic–photovoltaic electricity generator based on a biofilm of <italic>Synechocystis</italic> sp. PCC 6803, thereby eliminating the need for additional photosensitive materials. This generator integrates the inherent hydrovoltaic and photovoltaic properties of cyanobacteria, producing electricity via both effects during the day and exclusively via the hydrovoltaic effect at night, facilitating uninterrupted energy production at all times. Through synergistic hydrovoltaic–photovoltaic coupling, the device achieves a maximum open-circuit voltage of <sc>0.52 V</sc> and a short-circuit current of <sc>0.57 μA,</sc> with a specific power density of <sc>1.7×10⁻⁴ W/m</sc>², which is significantly better than the power density of independent moisture-driven generation <sc>(5×10⁻⁵ W/m</sc>²). Moreover, the biofilm retains substantial biological activity after prolonged electricity generation and enables linear amplification in series and parallel configurations, demonstrating its applicability in real-world scenarios. This research offers new insights into the development of next-generation continuous bio-based hydrovoltaic energy technologies.