Photothermally carbonized natural kelp for hydrovoltaic power generation

We have developed an eco-friendly and efficient method for hydrovoltaic power generation through carbonizing natural kelp, a hydrogel with abundant cations. Under ambient conditions, a CO2 laser beam was focused on the top surface of dried kelp, photothermally converting it into porous graphitic carbon (PGC) and reducing dissociable cations by thermal evaporation. Owing to the preservation of the bottom surface, this photothermal process yielded a PGC–hydrogel membrane (PHM) featuring a cation concentration gradient. With the introduction of deionized water to the intact region, the kelp hydrogel retained a considerable volume of water, creating a moist environment for the PGC. The cation concentration gradient facilitated a continuous migration of cations between the PGC and unaltered kelp, generating a voltage of 0.34 V and a current density of 49 μA/cm2. We demonstrated its practical applicability by turning on three light-emitting diodes using an array of eight PHMs. [Display omitted] •The hydrovoltaic power generator was developed using photothermally carbonized kelp•Kelp hydrogel functioned as a water reservoir and an ion supplier•The kelp-based HPG generated a voltage of 0.34 V and a current density of 49 μA/cm2 Chemistry; Chemical engineering; Electrochemistry; Electrochemical energy production.