Quantifying Electron and Ion Transfers in Contact Electrification with Ionomers

Abstract Electrostatic charging derived from charge transfer throughout friction is commonplace, but understanding the charge species transferred still remains a debated and contradictory issue. The electron has been widely believed to be the dominant charge carrier for contact electrification between solids, liquids, and gases. However, emerging evidence points to the trait that mobile ions can also contribute to the process, making it more complicated to elucidate even in solid–solid contact electrification. Here, it is demonstrated that electrons and ions concurrently play a role in solid contact‐electrification of solid‐ionomer pairs, and their contribution differs with environmental humidity levels. The results show that ionic charge transfer can improve contact electrification at high humidity levels of >50% RH. Moreover, adding ions to a non‐ionic polymer surface can make contact electrification more resistant to humidity. Overall, the findings highlight the significant role of concurrent electron and mobile ions in contact electrification, although only less than 2% of ions participate in the ion transfer, which can lead to new and improved technologies for electrophotography, electrospraying, energy harvesting, and self‐powered sensing.