Co doping regulating electronic structure of Bi2MoO6 to construct dual active sites for photocatalytic nitrogen fixation

Abstract

Although photocatalytic nitrogen reduction reaction (PNRR) is a green ammonia synthesis technology, it still encounters low adsorption/activation efficiency of N2 and lack of reaction active sites. Element doping is an efficient strategy to regulate electronic structure of catalyst. Nevertheless, the mechanism of the effect of doping elements on the N2 adsorption/activation, reaction active site and energy barriers is not well unraveled. Taking Co doped Bi2MoO6 (Co-Bi2MoO6) as a model photocatalyst, density functional theory (DFT) and experiment study were used to investigate the mechanism of Co doping on the PNRR performance over Bi2MoO6. DFT results reveal that Co doping regulates the electronic structure, activates Bi sites of Co-Bi2MoO6 and provides new Co active sites, thus constructing dual active sites for PNRR. Benefited from dual active sites for effectively adsorption/activation N2, the as-fabricated 3% Co-Bi2MoO6 exhibit the maximum NH3 generation rate of 95.5 μmol·g−1·h−1 without sacrificial agents, which is 7.2 times that of Bi2MoO6. Furthermore, the detail mechanism of NN bond adsorption/activation and hydrogenation reaction on Co-Bi2MoO6 was also proposed according to in-situ FTIR and DFT results. This study provides a promising strategy to design catalysts with dual active sites for PNRR, which is of great significance to the popularization of other material systems.