Recently, Yi Xie’s group made a new progress on synthesis and application of atomic-scale thickness single unit cell layers. The result was published in Angew. Chem. Int. Ed. (DOI: 10.1002/anie.201506966).

Artificial photosynthesis, which directly converts CO₂ and water on photocatalysts into valuable fuels using sunlight at room temperature and ambient pressure, has been regarded as one of the most promising and compelling strategies for simultaneously solving the energy and environmental problems. Although a few photocatalysts, such as sulfides, phosphides, and nitrides have been reported to be active for CO₂ photoconversion, these materials usually undergo serious photocorrosion under solar illumination on an aqueous environment. In contrast, oxide-based semiconductors are often more thermodynamically stable, and hence would be suitable candidates for solar-driven CO₂ conversion. Atomically-thin oxide-based semiconductors are proposed to promote solar CO₂ conversion by affording abundant catalytically active sites, increased two-dimensional conductivity, and superior structural stability, as an excellent platform which is first constructed by this work. Taking Bi₂WO₆ as an example, they proposed a lamellar hybrid intermediate strategy for successfully synthesizing atomic-scale thickness orthorhombic Bi₂WO₆ layers, taking advantage of an intermediate precursor lamellar Bi-oleate complex. The single-unit-cell thickness allows 3-times larger CO₂ adsorption capacity and higher photoabsorption than bulk Bi2WO6. Moreover, the temperature-dependent resistivity indicates that the single-unit-cell Bi₂WO₆ layers exhibit dramatically higher electronic conductivity relative to the bulk counterpart, which is consistent with their increased DOS near the Fermi level. The enhanced electronic conductivity would benefit the transport of photogenerated carriers. Time-resolved fluorescence emission decay spectra indicates the decay kinetics for single-unit-cell Bi₂WO₆ layers is much slower than that of bulk counterpart, in which their respective average fluorescence lifetimes are 83.2 and 14.7 ns, suggesting that the former could effectively reduce the recombination of the charge carriers. The result of photocatalyst for reduction of CO₂ demonstrates the single-unit-cell Bi₂WO₆ layers achieve a methanol formation rate of 75 μmol g^-1h^-1, 125-times higher than that of bulk Bi₂WO₆ and more stable meanwhile. This work will shed light on designing efficient and robust photoreduction CO₂ catalysts.



Paper links: http://onlinelibrary.wiley.com/doi/10.1002/anie.201506966/full