Design Principles to Maximize Non-Bonding States for Highly Tribopositive Behavior

The development of highly tribopositive materials is crucial for realizing high-performance triboelectric nanogenerators. In this study, a novel protocol to maximize the number of non-bonding electrons with local dipoles for designing highly tribopositive materials is introduced, and nitrogen-based dimethylol urea, diazolidinyl urea, and imidazolidinyl urea as promising tribopositive materials are suggested. The mechanism by which nitrogen-based materials provide highly tribopositive properties is investigated using calculations based on density functional theory. Highly electronegative atoms, such as nitrogen and oxygen, attract electrons from neighboring atoms, resulting in the formation of negative local dipoles in the highest occupied molecular orbital band composed of non-bonding electrons, thereby creating an electron-donating environment. The proposed design protocol is confirmed by quantitatively investigating the triboelectric properties of nitrogen-based materials, and analyzing the charge transfer characteristics of dimethylol urea based on dipole interactions.