Unraveling the Role of Cuprous Oxide and Boosting Solar Energy Conversion via Interface Engineering in Cu/TiO2 Plasmonic Photocatalyst
The photocatalytic performance and underlying mechanism of Cu modified TiO2 have attracted a wide range of scientific interest in recent years. However, the role of copper oxidation states on the localized surface plasmonic resonance (LSPR) effects and photocatalytic activity are still debated. Here, we utilize the finite-difference time-domain (FDTD) method to mimic spontaneous oxidation of Cu (e.g. Cu2O) in Cu/TiO2 hetero-structures and using density functional theory (DFT) to calculate the electronic structures of interfaces. On the basis of FDTD results, in the case of Cu@Cu2O/TiO2 configurations, it has found that the LSPR peak of Cu is directly modulated to near 650 nm, and the interfacial electric field intensity is weakened. In the case of Cu/TiO2/Cu2O configurations, in which Cu core and TiO2 nanoparticle can directly contact, it is successfully improved the interfacial electric field intensity generated by LSPR effects of Cu core. Moreover, the Fano resonance is introduced in Cu/TiO2/Cu2O configuration to further enhance the interfacial electric field enhancement. Meanwhile, the hot electrons generated by the LSPR effects of Cu core readily cross the lower Schottky barrier in Cu/TiO2 interface. Based on the analysis of electronic structures, the three types of band alignment may exist in the Cu/Cu2O/TiO2 ternary composite photocatalysts, and the possible electron transfer processes are discussed in details. Therefore, the LSPR effects (including: provide new absorption peaks in visible-light region, enhance interfacial electric field, produce hot electrons) of Cu core can be modulated by the thickness and position of Cu2O covering, which can be achieved by controlling the preparation conditions in practice. The existence of many kinds of interfaces in Cu/Cu2O/TiO2 ternary composite photocatalysts makes it possible and facility to design the fast separation and transmission channel of photo-generated carriers. The coupling of interface engineering and LSPR effects brings more available strategies and freedom degrees to promote the performance of Cu/Cu2O/TiO2 ternary composite photocatalyst. Therefore, careful optimization is necessary to make them synergistic boosting the photocatalytic performance of Cu/Cu2O/TiO2 ternary composites.