Black Titania and Niobia within Ten Minutes – Mechanochemical Reduction of Metal Oxides with Alkali Metal Hydrides

Abstract

Partially or fully reduced transition metal oxides show extraordinary electronic and catalytic properties but are usually prepared by high temperature reduction reactions. This study reports the systematic investigation of the fast mechanochemical reduction of rutile‐type TiO2 and H‐Nb2O5 to their partially reduced black counterparts applying NaH and LiH as reducing agents. Milling time and oxide to reducing agent ratio show a large influence on the final amount of reduced metal ions in the materials. For both oxides LiH shows a higher reducing potential than NaH. An intercalation of Li+ into the structure of the oxides was proven by PXRD and subsequent Rietveld refinements as well as 6Li solid‐state NMR spectroscopy. The products showed a decreased band gap and the presence of unpaired electrons as observed by EPR spectroscopy, proving the successful reduction of Ti4+ and Nb5+. Furthermore, the developed material exhibits a significantly enhanced photocatalytic performance towards the degradation of methylene blue compared to the pristine oxides. The presented method is a general, time efficient and simple method to obtain reduced transition metal oxides.

Designing Novel LiDAR-Detectable Plate-Type Materials: Synthesis, Chemistry, and Practical Application for Autonomous Working Environment

“…The main reason for selecting NaBH 4 as the reducing agent for the true blackness of HL/BT is its reduction potential. In particular, NaBH 4 can donate highly reactive hydride ions (H + ) and create Ti 3+ defects and oxygen vacancies in the TiO 2 lattice structure . Although ascorbic acid is also a widely used reducing agent, its reduction potential is lower than that of NaBH 4 and less effective in creating defects and vacancies in the TiO 2 lattice. − …”

“…In particular, NaBH 4 can donate highly reactive hydride ions (H + ) and create Ti 3+ defects and oxygen vacancies in the TiO 2 lattice structure. 34 Although ascorbic acid is also a widely used reducing agent, its reduction potential is lower than that of NaBH 4 and less effective in creating defects and vacancies in the TiO 2 lattice. 35−37 The fabrication process of plate-type HL/BT involved etching the glass template to form a hollow structure, followed by NaBH 4 reduction.…”

Influence of molecular orientation on the photodissociation process of LiH molecules

“…The LiH molecule is also an excellent hydrogen storage material, which has important applications in the development of new energy [13][14][15]. Meanwhile, it also has been used as nuclear protection materials and reducing agents [16][17][18]. Photodissociation is the process in which a molecule absorbs photons, leading to the breaking of chemical bonds within the molecule [19][20][21][22].…”

“…The LiH molecule is also an excellent hydrogen storage material, which has important applications in the development of new energy [13–15]. Meanwhile, it also has been used as nuclear protection materials and reducing agents [16–18].…”

Highly Exothermic and Fast Mechanochemical Redox and Intercalation Reactions of V2O5 with Sodium Hydride

“…28 We have recently shown that alkali metal hydrides are readily available and powerful reducing agents for the partial reduction of rutile-type TiO 2 and monoclinic H−Nb 2 O 5 in a fast and energy efficient ball milling process. 29 Thus, the question arises whether alkali metal hydrides can also be applied as reducing agents for the mechanochemical reduction of V 2 O 5 or if a simultaneous formation of alkali metal vanadates takes place. As for the reaction of V 2 O 5 with alkali metal hydrides, no excessive studies have been reported yet.…”