The development of energy‐conversion devices using water movement has actively progressed. Ionovoltaic devices, which are driven by ion dynamics, show ion specificity by which different ions with identical charges show different output performance. However, the ion specificity remains poorly understood because the influence of the ion species on generated electric signals is not elucidated. The ion specificity in electric signals induced by flowing water droplet was investigated in terms of its relationship with the potential profile across the solid–liquid interface.
Origin of ion specificity: The ionovoltaic device driven by droplet flow showed ion specificity by which different ions with identical charges shows different output performance. The origin of ion specificity at solid–liquid interface is investigated.