New polymer photocatalyst architectures for solar fuel generation

生产清洁能源和获得清洁水是材料化学领域的两个非常重要的当代挑战。这两个挑战都可以通过半导体催化的光催化过程来解决，其中水分解产生氢气，这是一种可储存的能量载体，或者将二氧化碳还原为太阳能燃料，以及光催化水消毒用于消除水中存在的细菌。为了使光催化水分解发生，需要半导体吸收光并产生电荷载流子，然后将电荷载流子转移到水中，从而产生氢气和氧气。直到最近，该领域一直由无机半导体（如二氧化钛）主导，通常与贵金属助催化剂结合。然而，2009年由Antonietti（Nat. Mater. 2009，8，76）引起了对用于水裂解的有机材料的兴趣的激增，绝大多数涉及氮化碳及其变体。在2015年，显示了共轭聚合物可以与碳氮化物竞争光催化析氢（J. Am. 2015，137，3265）和光催化二氧化碳还原（J. Mater.类似地，已经充分研究了使用二氧化钛的光催化水消毒，但是还需要UV光来产生，因为它是宽带隙材料。还发现无支链的共轭聚合物在光照下产生反应性物质，例如羟基和超氧化物自由基或过氧化氢，并且已经通过例如尚泽（Langmuir 2011，27，4956）和几项后续研究证明，这可以用于细菌灭活。共辄微孔聚合物也已显示出对于该应用是活性的（J. Mater.基本上，由于在有机材料中观察到的高激子结合能，这些过程在其效率上受到严重限制，这导致与无机光催化剂相比产生较少的电荷（Chem.Soc.Rev.2020，49，3981）。该项目将开发具有能量补偿的新材料架构，从而显著增强光催化氧化和还原反应的活性。这些材料将用于从水中产生氢气，减少二氧化碳和细菌灭活。一个特别的重点将是材料的加工性能，允许在未来的规模制造设备。

The production of clean energy and access to clean water are two very important contemporary challenges in materials chemistry. Both challenges can be addressed through photocatalytic processes catalysed by semiconductors with water splitting yielding hydrogen which is a storable energy carrier or the reduction of carbon dioxide into solar fuels, and photocatalytic water disinfection being used to inactivate bacteria present in water. For photocatalytic water splitting to occur a semiconductor is required that absorbs light and creates charge carriers that are then transferred to water resulting in hydrogen and oxygen production. Until recently, the field was dominated by inorganic semiconductors, such as titanium dioxide, often coupled with a precious metal co-catalyst. However, the 2009 Nature Materials report by Antonietti (Nat. Mater. 2009, 8, 76) has provoked a surge of interest in organic materials for water-splitting, the vast majority relating to carbon nitride and its variants. In 2015 it was shown that conjugated polymers can compete with carbon nitrides for photocatalytic hydrogen evolution (J. Am. Chem. Soc. 2015, 137, 3265) and photocatalytic carbon dioxide reduction (J. Mater. Chem. A, 2021, 9, 4291).Similarly, photocatalytic water disinfection with titanium dioxide has been well studied, but also requires UV light to create as it is a wide band-gap material. Unbranched conjugated polymers have also been found to generate reactive species, such as hydroxyl and superoxide radicals or hydrogen peroxide, under illumination and it has been demonstrated for example by Schanze (Langmuir 2011, 27, 4956) and several follow up studies that this can be used for bacteria inactivation. Conjugated microporous polymers have also been shown to be active for this application (J. Mater. Chem. B 2016, 4, 5112), but are far less explored to date.Fundamentally, these processes are severely limited in their efficiency due to the high exciton binding energies observed in organic materials which result in fewer charges being generated compared to inorganic photocatalysts (Chem. Soc. Rev. 2020, 49, 3981). The project will develop new material architectures with energy offsets that will result in significantly enhanced activity for photocatalytic oxidation and reduction reactions. The materials will be used for the generation of hydrogen from water, carbon dioxide reduction and bacteria inactivation. A particular focus will be on processability of the materials allowing for the fabrication of devices at scale going forward.