Black Nb₂O₅ nanorods with improved solar absorption and enhanced photocatalytic activity

Abstract

Black titania, with greatly improved solar absorption, has demonstrated its effectiveness in photocatalysis and photoelectrochemical cells (PEC), inspiring us to explore the blackening of other wide band-gap oxide materials for enhanced performance. Herein, we report the fabrication of black, reduced Nb2O5 nanorods (r-Nb2O5), with active exposed (001) surfaces, and their enhanced photocatalytic and PEC properties. Black r-Nb2O5 nanorods were obtained via reduction of pristine Nb2O5 by molten aluminum in a two-zone furnace. Unlike the black titania, r-Nb2O5 nanorods are well-crystallized, without a core-shell structure, which makes them outstanding in photocatalytic stability. Substantial Nb(4+) cation and oxygen vacancies (VO) were introduced into r-Nb2O5, resulting in the enhanced absorption in both the visible and near-infrared regions and improved charge separation and transport capability. The advantage of the r-Nb2O5 was also proved by its more efficient photoelectrochemical performance (138 times at 1.23 VRHE) and higher photocatalytic hydrogen-generation activity (13 times) than pristine Nb2O5. These results indicate that black r-Nb2O5 is a promising material for PEC application and photocatalysis.

Exploiting the Condensation Reactions of Acetophenone to Engineer Carbon‐Encapsulated Nb2O5 Nanocrystals for High‐Performance Li and Na Energy Storage Systems

“…The carbon content of the composites was varied between 0 and 16 wt% by changing the Nb 2 O 5 /TPB ratio, which was achieved by removing the desired amount of TPB with acetone. [48][49][50][51][52][53] They are dominated by the intense band (at 693 cm −1 ) arising from the symmetrical TO stretch of NbO bonds in the low distorted corner-or edgesharing bipyramidal units of the oxide lattice; [48,50,52] weaker bands are further detected at 122, 227, 308, 465, and 809 cm −1 . Small carbonencapsulated Nb 2 O 5 NCs (NP-X where X is the carbon content samples) were synthesized by reaction of NbCl 5 with acetophenone ( Figure 1c).…”

“…Spherical structures (400-600 nm) consisting of carbon-coated Nb 2 O 5 NCs (NS-X where X is the carbon content samples) were synthesized by reacting NbCl 5 in acetophenone in the presence of Co 2+ ions (Figure 1d). [52,53,55] The strongest band, associated with the bond order of the niobia polyhedra and structure order, [50,52,53] undergoes a downshift in all the composites but NP-10, where, on the contrary, it moves toward higher frequencies indicating that more ordered T-Nb 2 O 5 NCs are formed. [47] The carbon wt% in the carbonized samples was determined by thermogravimetric analysis ( Figure S7, Supporting Information).…”

One‐Step Synthesis of Nb2O5/C/Nb2C (MXene) Composites and Their Use as Photocatalysts for Hydrogen Evolution

“…The Raman spectra of Nb 2 CT x ,N CN-0.5, NCN-1.0, NCN-1.5, Nb 2 O 5 ,a nd Mix-NN are shown in Figure 1B.F rom Figure 1B, characteristic bands of Nb 2 O 5 at Ramans hifts of 233 (bending modes of NbÀOÀNb linkages), 688 (NbÀOs tretching mode), and 1000 cm À1 [vibration modeso fA 1 g(n 1 )o fN bO 6 octahedra] and somea dditional bands (492, 1457, and 1521 cm À1 )c orresponding to Nb 2 CT x can be observed clearly in the Raman spectrumo fo xidized Nb 2 CT x . [33,39] Moreover,t wo broad bands at Ramans hifts of 1362 and 1614 cm À1 are characteristic of the Da nd Gm odes of carbon species. The Db and demonstrates defects and partially disordered structures of sp 3 -hybridized carbon atoms, whereas the Gband is related to the in-plane vibrationm ode of the sp 2 -hybridized carbon atoms.…”

ZnSe/ZnO Nano-Heterostructures for Enhanced Solar Light Hydrogen Generation

“…Generally, semiconductor materials with proper band gap can be utilised as a photocatalyst for H 2 generation via water splitting. In the last few decades, various semiconductor materials were explored as photocatalyst viz., TiO 2 , ZnO, CdS, CdSe, WO 3 , MoS 2 , SrTiO 3 , Ta 2 O 5 , Nb 2 O 5 etc. Photocatalytic activity mainly depends on morphology, band gap and band positions, surface area and crystallanity of the materials .…”