Porous Ga O Nanotubes Derived from Urease-Mediated Interfacially-Grown NH Ga(OH) CO for High-Efficient Hydrogen Evolution.

The authors proposed a novel template-free strategy, urease-mediated interfacial growth of NH Ga(OH) CO nanotubes at 20-50 °C, to fabricate the porous Ga O nanotubes. The subtlety of the proposed strategy is all the products from urea enzymolysis are utilized in formation of NH Ga(OH) CO precipitates, and the key for interfacial growth of NH Ga(OH) CO nanotubes is the dynamic match between the rate of CO bubble fusion and NH Ga(OH) CO precipitation. The proposed strategy works well for the doped porous Ga O nanotubes. As a proof-of-concept, the porous β-Ga O and β-Ga O :Cr nanotubes are used as photocatalysts or co-catalysts with Pt, for H evolution from water splitting. The H evolution rate of porous β-Ga O nanotubes reach 39.3 mmol g h with solar-to-hydrogen (STH) conversion efficiency of 2.11% (Hg lamp) or 498 µmol g h with STH of 0.03% (Xe lamp) respectively, both about 3 times of β-Ga O nanoparticles synthesized at pH 9.0 without urease. The Cr-doping enhances the in-the-dark H evolution rate pre-lighted by Hg lamp, and Pt co-catalysis further elevates the H evolution rate, for instance, the H evolution rate of Pt-loaded β-Ga O :Cr nanotubes reaches 54.7 mmol g h with STH of 2.94% under continuous lighting of Hg lamp and 1062 µmol g h in-the-dark.