MOF-templated tubular Ni_(1−x)Co_(x)S_(2)-CdS heterojunction with intensified direct Z-scheme charge transmission for highly promoted visible-light photocatalysis

Hollow semiconductor nanostructures with direct Z-scheme heterojunction have significant advantages for photocatalytic reactions,and optimizing the interfacial charge transmission of Z-scheme heterojunction is the hinge to achieve excellent solar conversion efficiency.In this work,tubular Ni_(1−x)Co_(x)S_(2)-CdS heterostructures with reinforced Z-scheme charge transmission were constructed through an In-metal-organic framework(MOF)templated strategy.The Z-scheme charge transfer mechanism was sufficiently confirmed by combining density functional theory(DFT)calculation,X-ray photoelectron spectroscopy(XPS),surface photovoltage spectroscopy(SPV),and radical testing results.Crucially,the use of sodium citrate complexant contributes to the formation of intimate heterointerface,and the Fermi level gap between CdS and NiS_(2)is enlarged through Co doping into NiS_(2),which enhances the built-in electric field and photo-carriers transmission driving force for Ni_(1−x)Co_(x)S_(2)-CdS heterojunction,resulting in an evidently promoted activity toward H2 evolution reaction(HER).Under visible-light(λ>400 nm)irradiation,the Ni_(1−x)Co_(x)S_(2)-CdS composite with 10 mol%Co doping and 80 wt.%CdS(NC_(0.10)S-80%CdS)achieved an outstanding HER rate up to 35.94 mmol·g^(−1)·h^(−1)(corresponding to the apparent quantum efficiency of 34.7%at 420 nm),approximately 76.4 times that of 3 wt.%Pt-loaded CdS and it is much superior to that of most CdS-based photocatalysts ever reported.Moreover,the good photocatalytic durability of Ni_(1−x)Co_(x)S_(2)-CdS heterostructures was validated by cycling and long-term HER tests.This work could inspire the development of high-performance Z-scheme heterojunction via optimizing the morphology and interfacial charge transmission.