The creation of high-performance, reasonably priced, and environmentally benign materials is essential to the shift to sustainable energy systems. This chapter examines how sustainable materials, such as polymer compounds, nanomaterials, and bio-based substitutes, are essential to the development of clean energy technology. The materials’ uses in fuel cells, sensors, energy harvesting equipment, and piezoelectric devices—where they improve efficiency, lessen environmental impact, and allow for scalability—are highlighted. Nanostructured substances like graphene and nanotubes made of carbon (CNTs) offer better electrical, catalytic, and mechanical capabilities, while biodegradable polymers like chitosan, cellulose, along with silk fibroin offer flexible and environmentally friendly devices for sensors and energy harvesting. Sustainable triboelectric and piezoelectric energy harvesting technologies show promise for supplying power to Internet of Things (IoT) sensors and low-energy electronics. Similar to this, the use of catalysts generated from biomass and non-platinum group substitutes in fuel cells marks a significant advancement in lowering costs and environmental impact. Sustaining material stability under operating circumstances, guaranteeing large-scale production, and striking a balance between biodegradability and performance continue to be difficult tasks. Sustainable materials offer a revolutionary route toward environmentally friendly, effective, and scalable energy solutions by fusing developments in material science with device engineering. This aids in the global shift toward a cleaner and greener future.