Porous Ga2O3 Nanotubes Derived from Urease‐Mediated Interfacially‐Grown NH4Ga(OH)2CO3 for High‐Efficient Hydrogen Evolution

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 52
• Main Authors: Wang, Ting, Wang, Zheng‐Wu, Zhang, Ye, Yang, Xiao‐Ting, Zhu, Yi‐Zhou, Wang, He‐Fang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.12.2021
• Subjects: Catalysis; Ga 2O 3 nanotube; Gallium oxides; Hydrogen evolution; Nanoparticles; Nanotechnology; Nanotubes; NH 4Ga(OH) 2CO 3 nanotube; Precipitates; urease; Water splitting
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202104195

The authors proposed a novel template‐free strategy, urease‐mediated interfacial growth of NH4Ga(OH)2CO3 nanotubes at 20–50 °C, to fabricate the porous Ga2O3 nanotubes. The subtlety of the proposed strategy is all the products from urea enzymolysis are utilized in formation of NH4Ga(OH)2CO3 precipitates, and the key for interfacial growth of NH4Ga(OH)2CO3 nanotubes is the dynamic match between the rate of CO2 bubble fusion and NH4Ga(OH)2CO3 precipitation. The proposed strategy works well for the doped porous Ga2O3 nanotubes. As a proof‐of‐concept, the porous β‐Ga2O3 and β‐Ga2O3:Cr0.001 nanotubes are used as photocatalysts or co‐catalysts with Pt, for H2 evolution from water splitting. The H2 evolution rate of porous β‐Ga2O3 nanotubes reach 39.3 mmol g−1 h−1 with solar‐to‐hydrogen (STH) conversion efficiency of 2.11% (Hg lamp) or 498 µmol g−1 h−1 with STH of 0.03% (Xe lamp) respectively, both about 3 times of β‐Ga2O3 nanoparticles synthesized at pH 9.0 without urease. The Cr‐doping enhances the in‐the‐dark H2 evolution rate pre‐lighted by Hg lamp, and Pt co‐catalysis further elevates the H2 evolution rate, for instance, the H2 evolution rate of Pt‐loaded β‐Ga2O3:Cr0.001 nanotubes reaches 54.7 mmol g−1 h−1 with STH of 2.94% under continuous lighting of Hg lamp and 1062 µmol g−1 h−1 in‐the‐dark. A novel biological strategy via NH4Ga(OH)2CO3 nanotube intermediate is presented for fabrication of Ga2O3 nanotube. All species from urea enzymolysis are subtly used for the interfacial growth of NH4Ga(OH)2CO3 nanotube in aqueous solution of gallium salts at 20–50 °C, and the balance between the rate of CO2 bubble fusion and NH4Ga(OH)2CO3 precipitation is the key point.