Nakada Akinobu, Yokota Takayuki, Ogura Morihiko, Chang Ninghui, Tomita Osamu, Saeki Akinori, Ogasawara Masamichi, Abe Ryu
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan.
J Chem Phys. 2024 Jan 28;160(4). doi: 10.1063/5.0179225.
Dye-sensitized photocatalysts with molecular dyes and widegap semiconductors have attracted attention because of their design flexibility, for example, tunable light absorption for visible-light water splitting. Although organic dyes are promising candidates as metal-free photosensitizers in dye-sensitized photocatalysts, their efficiency in H2 production has far been unsatisfactory compared to that of metal-complex photosensitizers, such as Ru(II) tris-diimine-type complexes. Here, we demonstrate the substantial improvement of carbazole-thiophene-based dyes used for dye-sensitized photocatalysts through systematic molecular design of the number of thiophene rings, substituents in the thiophene moiety, and the anchoring group. The optimized carbazole-thiophene dye-sensitized layered niobate exhibited a quantum efficiency of 0.3% at 460 nm for H2 evolution using a redox-reversible I- electron donor, which is six-times higher than that of the best coumarin-based metal-free dye reported to date. The dye-sensitized photocatalyst also facilitated overall water splitting when combined with a WO3-based O2-evolving photocatalyst and an I3-/I- redox shuttle mediator. The present metal-free dye provided a high dye-based turnover frequency for water splitting, comparable to that of the state-of-the-art Ru(II) tris-diimine-type photosensitizer, by simple adsorption onto a layered niobate. Thus, this study highlights the potential of metal-free organic dyes with appropriate molecular designs for the development of efficient water splitting.
具有分子染料和宽带隙半导体的染料敏化光催化剂因其设计灵活性而备受关注，例如，可调节光吸收以用于可见光驱动的水分解。尽管有机染料作为染料敏化光催化剂中的无金属光敏剂是很有前途的候选物，但与金属配合物光敏剂（如钌（II）三二亚胺型配合物）相比，它们在制氢方面的效率一直不尽人意。在此，我们通过对噻吩环数量、噻吩部分的取代基以及锚定基团进行系统的分子设计，证明了用于染料敏化光催化剂的咔唑 - 噻吩基染料有显著改进。优化后的咔唑 - 噻吩染料敏化层状铌酸盐在使用氧化还原可逆的I⁻电子供体时，在460 nm处的析氢量子效率为0.3%，这比迄今报道的最佳香豆素基无金属染料高出六倍。当与基于WO₃的析氧光催化剂和I₃⁻/I⁻氧化还原穿梭介质结合时，该染料敏化光催化剂还促进了整体水分解。通过简单地吸附在层状铌酸盐上，这种无金属染料为水分解提供了与最先进的钌（II）三二亚胺型光敏剂相当的基于染料的高周转频率。因此，本研究突出了具有适当分子设计的无金属有机染料在开发高效水分解方面的潜力。
