Sustainable Hierarchical Wood/ZnO Piezoelectric Nanogenerators for Green Energy Harvesting

The increasing demand for sustainable and renewable energy sources has triggered significant research efforts in the field of energy harvesting. Among these technologies, low-cost and biodegradable piezoelectric nanogenerators have emerged as promising candidates for a wide range of applications.<br/> <br/>Nowadays, a growing demand has urged materials to be able to play an imperative role in sustainable energy harvesting, namely in piezoelectric mechanical energy conversion, since it is an attractive approach for mechanical energy harvesting. In response, wood, an abundant piezoelectric biomaterial, emerges as a promising sustainable material for harvesting mechanical energy, owing to its renewable origin, advanced hierarchical and porous structure, easy multi-functionalization and favourable mechanical properties.<br/> <br/>This work aims to contribute to the (r)evolution of Wood/ZnO nanohybrids by strategically modifying and tailoring wood substrates. This will open up new opportunities for expanding its performance into new advanced applications. The process involves delignification to increase wood porosity, followed by an oxidation process. It was observed that the oxidation process plays a crucial role in the performance of the devices. Hence, it can negatively charge the wood surface, allowing the accessibility to Zn²⁺ ions, leading to the growth of ZnO through a hydrothermal process at low temperatures.<br/>Combining the unique properties of wood with advanced nanomaterials leads to devices with output voltages above 9 V. In the work developed it was possible to maintain wood’s hierarchical structure and mechanical robustness after the fabrication of wood/ZnO composites with efficient mechanical energy conversion.