A high output power density triboelectric nanogenerator based on surface-patterned PI/UIO-66-NH ₂ mixed matrix membranes

Triboelectric nanogenerators (TENGs) have emerged as a promising technology to harvest energy from the environment due to their self-powered characteristics, simple structure, low cost and high flexibility. To improve their performance, this work proposes a hierarchical optimization strategy, which integrates the employment of a polyimide (PI) matrix, the doping of a metal-organic framework and the surface patterning of TENG triboelectric layers to achieve high output performance and durability. In this work, a PI/UIO-66-NH₂ mixed matrix membrane (MMM) is first synthesized and characterized, where the influence of UIO-66-NH₂ loading amount on the triboelectric properties of the MMM was analyzed. The measurement results show that this MMM exhibits excellent dielectric properties and thermal stability. Subsequently, a TENG device operating in the vertical contact-separation mode was fabricated, where the MMM was used as a negative triboelectric layer and a pure PI membrane was used as a positive layer. Moreover, the surface patterning method based on soft imprint lithography was applied to both triboelectric layers to augment their effective contact areas. Then, the output performance of the TENG was investigated. It is found that, for a weight ratio of UIO-66-NH₂ of 5 wt%, the patterned UIO-66-NH₂ MMM-based TENG (P-TENG-5) achieves a maximum output power density of 78.27 ± 3.42 μW cm^-2, which is 5.76 times higher than that of unpatterned TENG-5 and 361.35 times higher than that of pure PI-based TENG-0. Remarkably, P-TENG-5 maintained stable performance over 20 000 cycles at 2 Hz without considerable performance degradation.