Electrode Junction Effect for Enhanced Carrier Dynamics in Water Motion-Induced Electricity Generation

Water motion-induced energy harvesting has emerged as a promising approach to generating renewable electricity through the interaction between nanostructured two-dimensional materials and water. Despite growing interest, understanding the complex solid-liquid interfacial phenomena remains inconclusive mainly due to a lack of analytic approaches and interpretations regarding the nanoscopic interfacial regions, hindering practical advancements in energy harvesting efficiency. Herein, novel analytical approaches to water-induced charge carrier movement in semiconductors are proposed. Specifically, we employ various metal electrodes on reduced graphene oxide (rGO) to investigate its unique carrier density modulation behavior where the water contact region undergoes semiconductor-type inversion. The semiconductor type was confirmed through Hall effect measurements, and observations of I-V curves across wet and dry regions revealed a demonstration of diode characteristics. As semiconductor properties change in response to water interactions, the electrode junction effects also undergo ohmic/schottky contact reversal adjustment. Therefore, asymmetric electrode configurations were deposited on wet/dry regions to optimize carrier dynamics. By asymmetrically arranging metal electrodes at both ends of the rGO membrane, we observed significant enhancements in open-circuit voltage (Voc) and short-circuit current (Isc), reaching up to 1.05 V and 31.6 μA, respectively which is more than twice the voltage and 20-times the current compared to that of the rGO without the electrode deposition. These findings underscore the potential of customized electrode configurations on two-dimensional nanomaterials to enhance the efficiency and applicability of water motion-driven energy harvesting technologies.