Computational molecular modeling, i.e., density functional theory-based molecular modelling (DFT B3LYP/6-31-G*) (DFT/MM) verifies equilibrium geometry and surface electron energy structures of van der Waals force (vdW) molecular aggregates. What should be noted for the energy structures is that DFT/MM-predicted UV/Vis spectra are in good agreement with measured spectra of the aggregates.1) With these viewpoints, effective photoelectrochemical water splitting using mesoporous TiO2 anode and platinum cathode2), and effective water photo-splitting to HOOH and H2 on Pt-loaded TiO2 photocatalysts3) are reinvestigated by DFT/MM. DFT/MM-based UV/Vis spectrum analysis verifies that the anatase Yamashita & Jono’s model of HOTi9O18H has no absorption in the UV region, giving visible absorption spectrum with max=536 nm (strength 0.005). Then, DFT/MM was extended to vdW aggregates of smaller-size TiO2 clusters, (TiO2)n (n=1, 2, 4). Interestingly, DFT/MM-derived UV/Vis spectrum of (TiO2)4 shows max at 377 nm (strength 0.003), and the vdW aggregates of (TiO2)4 with H2O and with platinum triangle pole cluster of Pt6 validates that the molecular-structured TiO2 clusters, (TiO2)1~4 work as effective UV-induced photocatalysts2), and work as a UV-sensitizer in photoelectrochemical water splitting on biased TiO2 anode3).
1) Japanese Journal of Applied Physics 57, 121602 (2018).
2) Molecules 2015, 20(6), 9732-9744.
3) ECS Transactions, 80 (10) 1091-1112 (2017).


Dr. Shozo Yanagida is an emeritus professor of Osaka University since 2004 and a research director of “Research Association for Technological Innovation of Organic Photovoltaics” (RATO) of University of Tokyo. A year ago, he started research laboratory, “M3 Laboratory Inc.” in ISRI, Osaka University. When he was staying at SERI (now ENREL) as a visiting professor of Dr. A. Nozik’s group in 1984, he understand that organic and inorganic molecules have a strong tendency to aggregate each other via van der Waals and Coulomb interaction, forming two, three and four molecule aggregates, i.e., molecular structured aggregates. Now, he is focusing DFT/MM on functional materials as molecular vdW aggregates.