Modulating Contact Electrification With Metal‐Organic Frameworks in Flexible Triboelectric Nanogenerators for Kinetic Energy Harvesting and Self‐Powered Humidity Sensing Applications

Abstract

Herein, we present a novel method for fabricating a triboelectric nanogenerator using Polyacrylonitrile (PAN) on both sides as triboelectric pairs, incorporating metal-organic frameworks (MOFs) such as ZIF-8, ZIF-67, MIL-100, and HKUST-1 during the electrospinning process. The triboelectric properties of the MOF-incorporated fibers are thus tailored and positioned within the triboelectric series for the first time. The resulting triboelectric polarity of the composite fiber is linked to the optical bandgap energy of the PAN and the MOF/PAN composite, facilitating electron transfer between materials of different work functions and leading to enhanced output in the developed triboelectric devices. Fascinatingly, the appropriate choice of MOF filler also displayed the potential for reversing the triboelectric polarity of PAN nanofiber. Consequently, incorporating ZIF-8 and MIL-100 into PAN nanofibers led notably to contrasting trends in triboelectric polarity, with the pair generating an open-circuit output voltage of 100 V, short-circuit current of 1.35 μA, and a power density of 18.4 mW/m2 respectively. The fabricated device demonstrated effectiveness for mechanical energy harvesting applications and also as a self-powered humidity sensor, displaying rapid response to changes in ambient humidity levels with a maximum sensitivity of 2.14 V/%RH, for relative humidity range between 50 and 90% during the humidifying cycle.