Photo-induced charge boosting of liquid–solid electrokinetic generators for efficient wave energy harvesting

Film-type electrokinetic generators are a cost-effective and robust strategy for harvesting multi-frequent ocean wave energy. However, the intrinsic property of a low charge density prevents the generator from further improving the energy conversion efficiency. Herein, we present a photo-induced charge-boosting liquid–solid electrokinetic generator (L-SEKG) with a structure of polyurethane/graphene oxide-carbon black-multi-walled carbon nanotube/carbon quantum dots/copper (PU/GO-CB-MWCNT/CQDs/Cu) to harvest ocean wave energy. Systematic studies on the relationship between the output performance and GO dosage, MWCNT dosage, wave frequency, seawater temperature, CQD dosage and illumination intensity respectively were performed to optimize the energy conversion efficiency. Under standard sun illumination (100 mW cm−2, air mass 1.5), a maximum voltage of 0.1 V, a current of 0.39 mA and a power density of 26.6 mW m−2 were achieved by the L-SEKG with a GO/CB ratio of 4 : 3, a MWCNT dosage of 17%, a wave frequency of 0.9 Hz and at a temperature of 25 °C. Further, a stability test of L-SEKG was conducted under continuous waving using real seawater, and a circuit design for scaling up the power output is presented as well. The results demonstrate that the photo-induced L-SEKG has promising applications in large-scale networks to scavenge water wave energy efficiently.