Crake Angus, Christoforidis Konstantinos C, Gregg Aoife, Moss Benjamin, Kafizas Andreas, Petit Camille
Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK.
Department of Chemistry, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK.
Small. 2019 Mar;15(11):e1805473. doi: 10.1002/smll.201805473. Epub 2019 Feb 4.
CO photoreduction to C /C energized molecules is a key reaction of solar fuel technologies. Building heterojunctions can enhance photocatalysts performance, by facilitating charge transfer between two heterojunction phases. The material parameters that control this charge transfer remain unclear. Here, it is hypothesized that governing factors for CO photoreduction in gas phase are: i) a large porosity to accumulate CO molecules close to catalytic sites and ii) a high number of "points of contact" between the heterojunction components to enhance charge transfer. The former requirement can be met by using porous materials; the latter requirement by controlling the morphology of the heterojunction components. Hence, composites of titanium oxide or titanate and metal-organic framework (MOF), a highly porous material, are built. TiO or titanate nanofibers are synthesized and MOF particles are grown on the fibers. All composites produce CO under UV-vis light, using H as reducing agent. They are more active than their component materials, e.g., ≈9 times more active than titanate. The controlled composites morphology is confirmed and transient absorption spectroscopy highlights charge transfer between the composite components. It is demonstrated that electrons transfer from TiO into the MOF, and holes from the MOF into TiO , as the MOF induces band bending in TiO .
将一氧化碳光还原为碳/碳激发分子是太阳能燃料技术的关键反应。构建异质结可以通过促进两个异质结相之间的电荷转移来提高光催化剂的性能。然而，控制这种电荷转移的材料参数仍不清楚。在此，我们假设气相中一氧化碳光还原的控制因素为：i）具有大孔隙率，以便在催化位点附近积累一氧化碳分子；ii）异质结组分之间有大量“接触点”，以增强电荷转移。前一个要求可以通过使用多孔材料来满足；后一个要求则通过控制异质结组分的形态来实现。因此，构建了氧化钛或钛酸盐与金属有机框架（MOF，一种高度多孔的材料）的复合材料。合成了二氧化钛或钛酸盐纳米纤维，并在纤维上生长了MOF颗粒。所有复合材料在紫外-可见光下以氢气作为还原剂产生一氧化碳。它们比其组成材料更具活性，例如，比钛酸盐活性高约9倍。证实了复合材料形态的可控性，瞬态吸收光谱突出了复合组分之间的电荷转移。结果表明，由于MOF在二氧化钛中引起能带弯曲，电子从二氧化钛转移到MOF中，空穴从MOF转移到二氧化钛中。
