Tailoring the Electron-Rich Moiety in Benzothiadiazole-Based Polymers for an Efficient Photocatalytic Hydrogen Evolution Reaction
Tailoring the Electron-Rich Moiety in Benzothiadiazole-Based Polymers for an Efficient Photocatalytic Hydrogen Evolution Reaction
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DOI：
10.1021/acs.jpcc.9b06057
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发表时间：
2019-10-24
影响因子：
3.7
通讯作者：
Araujo, C. Moyses
中科院分区：
文献类型：
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作者：
Damas, Giane B.;Marchiori, Cleber F. N.;Araujo, C. Moyses
含有延伸的π-共轭主链的聚合物材料已经显示出广泛的适用性，包括用于析氢反应（HER）的光催化活性。后者需要高效的材料，具有最佳的光吸收和电荷转移过程的热力学驱动力，通过连接具有不同电子亲和力的化学单元以形成供体-受体结构来定制这些特性。在这里，这一概念是探索通过从头算理论在苯并噻二唑基聚合物与不同的富电子部分，即，芴（PFO）、环戊二烯并噻吩（CPT）、甲氧基苯并二噻吩（O-BzT）、噻吩并二噻吩（T-BzT）、以及噻吩（T，VT）-和噻吩并噻吩（TT，VTT）-基单元。所有材料相对于参比聚合物（PFO-DT-BT）表现出红移的吸收光谱，同时保持制氢的催化能力几乎不变。特别地，在CPT-VTT-BT中结合具有高施主特征的化学单元时，在第一吸收最大值中实现了Δ λ = 167 nm的位移。此外，激子结合能（E-b）已被系统地研究，揭示几何弛豫，环境极性，和有限的温度贡献的自由能的影响。例如，当从气相（E-b = 1.43-1.85 eV）到溶剂环境（在1-溴辛烷中E-b = 0.29-0.54 eV，λ = 5.02）时，我们显示E-b的显著变化。此外，我们还发现，激子结合能的降低与施主和受主对HOMO轨道贡献的比值的增加之间存在线性相关性。这是电子-空穴对的贡献能力增加和空间分离增强的结果，这削弱了它们的相互作用。最后，我们的研究结果表明，供体单元起着至关重要的作用，在关键的属性，支配的光催化活性的供体-受体聚合物有助于开发一个实用的指导方针，以设计更有效的光催化剂的HER。这经历了一个适当的组合的富电子部分，以调整光学间隙，有利于电荷转移的热力学驱动力，和较低的激子结合能。
Polymeric materials containing an extended pi-conjugated backbone have shown a wide range of applicability including photocatalytic activity for the hydrogen evolution reaction (HER). The latter requires highly efficient materials with optimal light absorption and thermodynamic driving force for charge transfer processes, properties that are tailored by linking chemical units with distinct electron affinity to form a donor-acceptor architecture. Here, this concept is explored by means of ab initio theory in benzothiadiazole-based polymers with varying electron-rich moieties, viz., fluorene (PFO), cyclopentadithiophene (CPT), methoxybenzodithiophene (O-BzT), thiophenebenzodithiophene (T-BzT), and thiophene (T, VT)- and thienethiophene (TT, VTT)-based units. All materials exhibit a red-shifted absorption spectrum with respect to the reference polymer (PFO-DT-BT) while keeping the catalytic power for hydrogen production almost unchanged. In particular, a displacement of Delta lambda = 167 nm in the first absorption maximum has been achieved upon combination of chemical units with high donating character in CPT-VTT-BT. Furthermore, the exciton binding energies (E-b) have been systematically investigated to unveil the effects of geometry relaxation, environment polarity, and finite temperature contributions to the free energy. For instance, we show a significant change in E-b when going from the gas phase (E-b = 1.43-1.85 eV) to the solvent environment (E-b = 0.29-0.54 eV in 1-bromooctane with epsilon = 5.02). Furthermore, we have found a linear correlation between the lowering of exciton binding energies and the increasing of the ratio between donor and acceptor contributions to the HOMO orbital. This is a consequence of increased donating ability and enhanced spatial separation of electron-hole pairs, which weakens their interaction. Finally, our findings reveal that the donor unit plays a crucial role in key properties that govern the photocatalytic activity of donor-acceptor polymers contributing to the development of a practical guideline to design more efficient photocatalysts for the HER This goes through a proper combination of electron-rich moieties to tune the optical gap, favor thermodynamic driving force for charge transfer, and lower exciton binding energies.