Warnan Julien, Willkomm Janina, Ng Jamues N, Godin Robert, Prantl Sebastian, Durrant James R, Reisner Erwin
Christian Doppler Laboratory for Sustainable SynGas Chemistry , Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK . Email:
Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK.
Chem Sci. 2017 Apr 1;8(4):3070-3079. doi: 10.1039/c6sc05219c. Epub 2017 Feb 3.
A series of diketopyrrolopyrrole (DPP) dyes with a terminal phosphonic acid group for attachment to metal oxide surfaces were synthesised and the effect of side chain modification on their properties investigated. The organic photosensitisers feature strong visible light absorption ( = 400 to 575 nm) and electrochemical and fluorescence studies revealed that the excited state of all dyes provides sufficient driving force for electron injection into the TiO conduction band. The performance of the DPP chromophores attached to TiO nanoparticles for photocatalytic H evolution with co-immobilised molecular Co and Ni catalysts was subsequently studied, resulting in solar fuel generation with a dye-sensitised semiconductor nanoparticle system suspended in water without precious metal components. The performance of the DPP dyes in photocatalysis did not only depend on electronic parameters, but also on properties of the side chain such as polarity, steric hinderance and hydrophobicity as well as the specific experimental conditions and the nature of the sacrificial electron donor. In an aqueous pH 4.5 ascorbic acid solution with a phosphonated DuBois-type Ni catalyst, a DPP-based turnover number (TON) of up to 205 was obtained during UV-free simulated solar light irradiation (100 mW cm, AM 1.5G, > 420 nm) after 1 day. DPP-sensitised TiO nanoparticles were also successfully used in combination with a hydrogenase or platinum instead of the synthetic H evolution catalysts and the platinum-based system achieved a TON of up to 2660, which significantly outperforms an analogous system using a phosphonated Ru tris(bipyridine) dye (TON = 431). Finally, transient absorption spectroscopy was performed to study interfacial recombination and dye regeneration kinetics revealing that the different performances of the DPP dyes are most likely dictated by the different regeneration efficiencies of the oxidised chromophores.
合成了一系列带有末端膦酸基团以附着在金属氧化物表面的二酮吡咯并吡咯（DPP）染料，并研究了侧链修饰对其性能的影响。这些有机光敏剂具有强烈的可见光吸收（λ = 400至575 nm），电化学和荧光研究表明，所有染料的激发态都为电子注入TiO导带提供了足够的驱动力。随后研究了附着在TiO纳米颗粒上的DPP发色团与共固定化的分子Co和Ni催化剂用于光催化析氢的性能，从而在不含贵金属成分的情况下，通过悬浮在水中的染料敏化半导体纳米颗粒系统实现了太阳能燃料的生成。DPP染料在光催化中的性能不仅取决于电子参数，还取决于侧链的性质，如极性、空间位阻和疏水性，以及特定的实验条件和牺牲电子供体的性质。在含有膦酸化的杜波依斯型Ni催化剂的pH 4.5的抗坏血酸水溶液中，在无紫外光模拟太阳光照射（100 mW cm²，AM 1.5G，λ > 420 nm）1天后，基于DPP的周转数（TON）高达205。DPP敏化的TiO纳米颗粒还成功地与氢化酶或铂结合使用，代替了合成析氢催化剂，基于铂的系统实现了高达2660的TON，这显著优于使用膦酸化的钌三联吡啶染料的类似系统（TON = 431）。最后，进行了瞬态吸收光谱研究界面复合和染料再生动力学，结果表明DPP染料的不同性能很可能是由氧化发色团的不同再生效率决定的。
