In-situ anion exchange based Bi_(2)S_(3)/OV-Bi_(2)MoO_(6)heterostructure for efficient ammonia production:A synchronized approach to strengthen NRR and OER reactions

摘要

Photocatalytic ammonia generation via nitrogen reduction reaction(NRR)is a green and prospective nitrogen fixation technique.However,NRR is often hampered by the high N_(2) adsorption/activation energies and is accompanied by a slow kinetics oxygen evolution reaction(OER).Herein,a robust Bi_(2)S_(3)/OVBi_(2)MoO_(6)S-scheme heterojunction is constructed using a simple in-situ anion exchange process,which enables oxygen vacancy(OVs)abundant Bi_(2)Mo O_(6) microspheres with surface deposited Bi_(2)S_(3).The asfabricated Bi_(2)S_(3)/OVBi_(2)MoO_(6) functioned as an effective photocatalyst to convert N_(2)-to-NH_(3) under mild conditions.The photocatalytic NH_(3)/NH_(4)^(+) production rate reached 126μmol g_(cat)^(-1)under visible light for2.5 h with 2%of Bi_(2)S_(3)/OVBi_(2)MoO_(6)photocatalyst,which was 8-fold higher than pristine Bi_(2)MoO_(6).Furthermore,the as-fabricated Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction exhibited good selectivity,high stability and reproducibility.The excellent photocatalytic NRR performance was ascribed to the Bi_(2)S_(3)/Bi_(2)MoO_(6)heterojunction formed subsequent to the strong interaction between Bi_(2)S_(3)and Bi_(2)MoO_(6).The OVs facilitated the chemical adsorption process allowing activation of N_(2)molecule on the Bi_(2)S_(3)/Bi_(2)MoO_(6).Simultaneously,the S-scheme heterojunction prolonged the lifetime of photogenerated carriers,accelerated the electrons/holes spatial separation and accumulation on the Bi_(2)S_(3)(reduction)and Bi_(2)MoO_(6)side(oxidation),respectively,thus strengthening both OER and NRR half-reactions.This simple in-situ anion exchange method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based photocatalysts for effective photocatalytic ammonia generation.