S vacancies act as a bridge to promote electron injection from Z-scheme heterojunction to nitrogen molecule for photocatalytic ammonia synthesis

Abstract

• BiVO 4 /ZnIn 2 S 4 heterojunction rich in sulfur vacancy (BVO/S v -ZIS) were used for pNRR. • Without sacrificial reagent, the ammonia generation rate reached 80.6 μmol·g −1 ·h −1 . • Sulfur vacancy (S v ) is the active site of N 2 chemisorption. • Photogenerated electrons are transferred to N 2 molecules with S v as a bridge. • Efficiency of electron injection into N 2 molecules on heterojunction was enhanced. The low efficiency of photogenerated electron injection into N 2 molecule is the key problem to limit the improvement of activity for photocatalytic ammonia synthesis of heterojunction materials. In this paper, BiVO 4 /ZnIn 2 S 4 direct Z-scheme heterojunction rich in sulfur vacancies (BVO/S v -ZIS) were synthesized by solvothermal method and used for photocatalytic nitrogen reduction reaction (pNRR). Without sacrificial reagent, the ammonia generation rate reached 80.6 μmol·g −1 ·h −1 , which is 3.5 times and 4.5 times higher than that of pristine BVO and ZIS, respectively. The results of N 2 -TPD, XPS and DFT calculation show that sulfur vacancy (S v ) is not only the active site of N 2 chemisorption, but also can capture photogenerated electrons and change the local electronic structure on the surface of heterojunction. The photogenerated electrons are continuously transferred to N 2 molecules with S v as a bridge, so as to break the barrier and enhance the efficiency of electron injection into N 2 molecules during pNRR on heterojunction.