Ultrathin TiO2 flakes optimizing solar light driven CO2 reduction

Abstract Photoreduction of CO 2 into fuels over TiO 2 helps to relieve the increasing energy crisis and the worsening global climate, while the low energetic efficiency impedes its large-scale applications. Herein, ultrathin TiO 2 flakes are first put forward to fully optimize their crucial CO 2 photoreduction processes through affording abundant catalytically active sites and increased two-dimensional conductivity. 1.66 nm thick TiO 2 flakes are successfully fabricated by virtue of lamellar TiO − 2 octylamine hybrid. The atomic thickness endows TiO 2 with ultrahigh fraction of surface atoms, which ensures stronger UV light absorption compared with its bulk counterpart. Benefiting from the increased density of states near Fermi level and the vast majority of charge density concentrating on the surface, the ultrathin TiO 2 flakes show increased conductivity confirmed by the temperature-dependent resistivities. The 3 times higher fluorescence lifetime, revealed by the time-resolved fluorescence spectroscopy, accounts for the increased separate rate of photoexcited electron-hole pairs. As an outcome, the ultrathin TiO 2 flakes achieve a formate formation rate of 1.9 μmol g −1  h −1 , 450 times higher than that of bulk counterpart and also roughly 2 times higher than that of previously reported Ag-modified BaLa 4 Ti 4 O 15 . Briefly, our study will unlock many opportunities for designing efficient CO 2 photoreduction performance.