Ionovoltaics in energy harvesting and applications: A journey from early development to current state-of-the-art

Ionovoltaics is a breakthrough concept in energy conversion that harnesses water motion with ion dynamics to generate electrical energy. This phenomenon is based on the interaction between the nanoscopic ionic behavior at the solid-liquid interface and the flow of electrons in a semiconductor electrode. Ionovoltaic research aims to present the most rational and convincing mechanism for the much-debated principle of energy conversion by water motion through a deeper understanding of solid-liquid interfacial phenomena and to discuss the potential to transform related fields through the development of enabling technologies such as novel energy harvesters, interfacial analysis tools, and bio/chemical sensors. Furthermore, efforts to develop high-efficiency ionovoltaic device powered by small water droplets indicate a potential contribution to the advancement of green energy systems that complement solar and wind power generation and address environmental pollution and energy shortages. This review paper explores the evolution of energy harvesting technologies using water motion, with a particular focus on ionovoltaics as an emerging field. By establishing the fundamentals, this study investigates solid-liquid interfaces, semiconductor properties, and natural water motion-driven ionovoltaic phenomena and also highlights that extensive research on complex ion/interface phenomena can have practical applications in diverse industrial fields.