In Situ Driven Formation of Anatase/Brookite/Rutile Heterojunction N/TiO2 Nanocrystals as Sustainable Visible‐Light Catalysts

• Published in: Global challenges 2024-10, Vol.8 (10), p.2400174-n/a
• Main Authors: Assayehegn, Elias, Solaiappan, Ananthakumar, Gidey, Abraha Tadese, Gebreegziabher, Gebremedhin Gebremariam, Gebretsadik, Tesfamariam Teklu, Chebude, Yonas, Alemayehu, Esayas
• Format: Article
• Language: English
• Subjects: Aging; Anatase; Brookite; Charge transfer; Controllability; Crystal structure; Crystals; Current carriers; Degradation; doping; Efficiency; Electromagnetic absorption; Energy charge; Guanidine hydrochloride; Heterojunctions; Heterostructures; Irradiation; Light; Light irradiation; Methylene blue; Nanocomposites; nanocrystals; Nanomaterials; Nanoparticles; Nanotechnology; Optical properties; Phase composition; phase transformation; Photocatalysis; photocatalyst; Physicochemical properties; Rutile; Sol-gel processes; Synergistic effect; TiO2; Titanium dioxide
• ISSN: 2056-6646; 2056-6646
• DOI: 10.1002/gch2.202400174

Visible‐light active anatase/brookite/rutile (A/B/R) ternary N‐doped titania (N/TiO2) crystals are successfully prepared by a facile sol‐gel method using titanium butoxide and benign N‐dopant source, guanidinium chloride. Systematically varying the aging time (1, 4, 8, and 12 d), its influence on physicochemical properties of as‐obtained spherical heterojunction nanomaterials is studied. Detailed characterizations confirm that a substantial amount of anatase (88% to 50%) is transformed to rutile (2% to 38%) via intermediate brookite phase (9% to 25%) as the function of aging time; not only the A/B/R phase content of the samples is tuned by sol‐gel aging time of the precursors solution but also their optical‐response and methylene blue photocatalytic properties are profoundly dictated. Notably under visible‐light irradiation, the photostable rutile rich mesoporous A/B/R triphasic N/TiO2 (50% A, 12% B, 38% R) aged for 12 d demonstrates higher degradation activity (97%) with a faster degradation rate (0.033 min−1) than both lesser aged N/TiO2 and undoped titania. This enhancement is attributed to the synergistic effect of interstitial‐N‐doping and optimal A/B/R interfacial charge transfer that leads to higher light absorption, lower bandgap energy and well‐separated charge carriers. The current work provides a new perspective for designing highly active visible‐light heterostructure nanomaterials with controllable phase composition. In this study, tunable anatase/brookite/ rutile ternary N/TiO2 nanocrystals with well‐separated charge carriers are prepared by varying the aging time, often overlooked, which significantly influence the structure, morphology, optical response, and photoactivity. More importantly, this study reveals the importance of sol‐gel aging along with its in situ phase‐heterojunction formation, in addressing the inherent defects of TiO2 for energy and environmental remediation.