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

Abstract 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:Cr_0.001 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:Cr_0.001 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.