Band Structure Engineering of Transition-Metal-Based Layered Double Hydroxides toward Photocatalytic Oxygen Evolution from Water: A Theoretical-Experimental Combination Study

Considerable attention has been focused on layered double hydroxides (LDHs) for their applications in solar energy storage and conversion recently, but the in-depth investigation on the semiconducting properties of LDHs is limited. Herein, the electronic properties (band structure, density of states (DOS), surface energy, and band edge placement) of 14 kinds of (MnMIII/IV)-M-II-A-LDHs (M-II = Mg, Co, Ni, Cu, Zn; M-III = Cr, Fe; M-IV = Ti; n = 2, 3, 4; A = Cl-, NO3-, CO32-) which contain transition-metal cations as well as their thermodynamic reaction mechanism toward the oxygen evolution reaction (OER) were studied using a density functional theory plus U (DFT + U) method. The calculation results indicate that the (003) plane is the most preferably exposed surface, and all these calculated LDHs are visible light responsive. The OER driving force and overpotential for these LDHs were obtained via their band edge placement and thermodynamic mechanism, and the results show that 10 of the calculated 12 LDHs (Ni2Ti-Cl-, Cu2Ti-Cl-, Zn2Ti-Cl-, Ni2Cr-Cl-, Zn2Cr-Cl-, Co2Fe-Cl-, Ni2Cr-NO3-, Ni2Cr-CO3-, Ni3Cr-Cl-, and Ni4Cr-Cl-LDHs) can overcome the reaction barriers by virtue of their driving force of photogenerated hole. Experimental observations further prove that NinCr-A-LDHs (n = 2, 3, 4; A = Cl-, NO3-, CO32-) are efficient OER photocatalysts, among which Ni2Cr-Cl-LDH shows the most active photocatalytic OER performance (O-2 generation rate 1037 mu mol h(-1) g(-1)). In the meantime, Mg2Cr-Cl-LDH has no OER activity, agreeing well with the theoretical prediction. This work provides theoretical insight into the photocatalytic OER performance of LDHs materials which contain transition-metal cations with semiconducting property, which would show potential application in optical/optoelectronic field.