Ultrathin-Walled 3D Inorganic Nanostructured Networks Templated from Cross-Linked Cellulose Nanocrystal Aerogels

A key challenge in the development of materials for applications in the fields of opto- and nanoelectronics, catalysis, separation, and energy conversion is the ability to fabricate 3D inorganic semiconductive nanostructures in a precisely-controlled and cost-effective manner. This work describes the fabrication of 3D nanostructured TiO₂ monoliths by coating ultraporous cross-linked cellulose nanocrystal (CNC) aerogel templates with TiO₂ layers of controlled thickness via atomic layer deposition (ALD). Following calcination, the resulting hollow inorganic ultraporous 3D networks form the thinnest self-supporting semiconductive structure (7 nm) fabricated directly on a conductive substrate. The CNC-templated ALD–TiO₂ electrodes are applied toward photoelectrochemical water splitting. The results show that a TiO₂ coating as thin as 15 nm produces a maximum water splitting efficiency, resulting in materials savings and reduced fabrication time.