Adsorption-induced surface potential modulation and electron transfer of solid-solid triboelectric nanogenerators under gas atmospheres

Abstract

Environmental factors have a significant impact on triboelectric charging, such as temperature, humidity, and pressure. The atmosphere also influences the output of TENGs, but this is often overlooked. To investigate how the atmosphere affects the output of TENGs under atmospheric pressure, a sealed system was constructed to create homogeneous atmospheres of air, O₂, N₂, and Ar. It was found that under a humidity of 20% RH, the TENG achieved maximum output in air. Then, the volume ratio of oxygen to nitrogen is refined, finding that the TENG achieved the maximum output at a ratio of 2:8. To explain how gases affect the output of TENGs, a mechanistic analysis was provided from three aspects: charge generation, accumulation, and dissipation. DFT calculations suggest that different gases have varying adsorption capacities on the contact surface, which alters the surface free energy of the solid, thereby changing the surface potential. The adsorption of gases modifies the relative positions of the HOMO and LUMO orbitals, affecting the energy difference and thus influencing the ease of electron transfer. This leads to changes in the generation and accumulation of triboelectric charges. Simultaneously, the measured charge dissipation rates exhibit certain variations, indicating that different atmospheres also have varying effects on charge decay. Furthermore, the output patterns of TENGs were also studied in different atmospheres at higher humidity and temperature levels. Finally, based on the different output signals of the TENGs in various atmospheres, a gas detection sensor was designed that can be used to identify different types of gases.