Moisture, Sweat, and Rainwater-Driven Hydrovoltaic Cell Based on 2D Borophene Nanosheets as Charge Trapping Layer to Harvest Electrical Energy for Self-Powering Electronics and Gas Sensor

The development of self-powered devices offers a promising future for next-generation technologies useful in consumer electronics. Despite significant progress in this area, achieving wearable and adaptable sensing devices with miniaturized stable power sources continues to be highly desirable but challenging. Hence, in this work, we have developed a borophene-based hydrovoltaic cell and demonstrated it as an efficient energy harvester for self-powering a variety of electronic devices. The sono-chemically synthesized nanosheet structured two-dimensional borophene has been confirmed through Raman spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. For the fabrication of a hydrovoltaic cell, borophene is coated on a carbon cloth, over which an electric double layer is formed due to the interaction of water to trap charges like an electrolytic capacitor. To achieve the asymmetric structure in the hydrovoltaic cell, two different coatings (namely a PVA/LiCl hygroscopic gel and a TiO2 hydrophobic coating) have been applied over the borophene-coated carbon cloth in an interdigitated mannered structure. A durable in-plane potential difference emerges across the hygroscopic and hydrophobic coating. The power density of the hydrovoltaic cell is calculated as 37.5 μW/m2. Other than moisture, the as-fabricated hydrovoltaic cell yields a 0.3–0.35 V output voltage in the presence of artificial sweat and freshwater droplets (as raindrops). The device’s capacitive characteristics highlights its versatility as both an energy storage component and a power supplier for small electronics like LEDs. Additionally, it is able to successfully power a ZnO-based gas sensor to detect ethanol gas molecules. This innovative approach paves the way for integrating self-powered sensors in wearable electronics, enhancing their sustainability, portability, and functionality.