Diatom Biosilica: Extraction Techniques and Applications in Energy Storage and Conversion Devices

The shift toward sustainable energy technologies requires materials with high performance and environmental compatibility. Traditional electrode and storage materials made of synthetic silica are usually constrained by high manufacturing costs and energy-intensive processing, raising questions about environmental sustainability. Biosilica from diatoms presents a unique alternative with hierarchically porous architectures, high surface area, mechanical stability, and chemically tunable surfaces, which may provide promising sustainable material source. This review critically evaluates the biological origin of diatoms, recent advances in extraction, and purification techniques for biosilica, including chemical, thermal, plasma-assisted, hydrothermal liquefaction, and hybrid approaches, and the physicochemical characteristics of biosilica. This review also investigates diatom biosilica as a functional material for energy conversion and storage. Emerging strategies involving hybridization with carbon nanomaterials, metal oxides, and conductive polymers are discussed in the context of structure-function relationships. Furthermore, we explore the challenges associated with scalability, morphology control, interface engineering, and integration into flexible and wearable systems. Finally, we outline future directions in biosilica research, emphasizing bioengineering approaches and application-driven material design. By bridging microbiology, materials science, energy technology, and diatom biosilica offers a uniquely sustainable and tunable nanomaterial for next-generation energy and environmental systems.