Co₃O₄@ZnIn₂S₄ Core-shell Heterostructure Construction And Solar Photothermal Catalytic Hydrogen Production Study

In today’s world,the energy crisis and environmental pollution problems are becoming increasingly serious.Hydrogen energy is attracting attention as a clean and efficient green energy source,and the conversion of solar energy to hydrogen energy using photocatalytic technology with semiconductor materials as the core is considered to be a very promising strategy.Zn In₂S₄（ZIS）as a kind of trimetallic sulfide semiconductor material,has been widely concerned in the field of photocatalysis due to its strong visible light response,suitable band gap.However,ZIS also has some disadvantages such as high photocarrier recombination rate.The construction of heterojunction is an important way to improve carrier separation to achieve efficient photocatalytic hydrogen production.The photothermal effect is an effective strategy to accelerate carrier separation and surface reaction kinetics.The efficient combination of the two will significantly improve the catalytic activity of the catalyst.However,the related photothermal mechanism based on heterojunction is not clear enough and needs to be further explored.In this paper,we prepared the photocatalyst Co₃O₄@ZIS by in-situ growing ZIS nanosheets on the surface of the photothermal material Co₃O₄,and constructed an integrated photothermal/photocatalytic system.P-n heterostructures were formed by the close contact between Co₃O₄（p-type semiconductor）and ZIS（n-type semiconductor）,which promoted the rapid separation of photogenerated carriers under the effect of the built-in electric field at the interface between them and prolonged the carrier lifetime.The introduction of Co₃O₄ broadened the photoabsorption range of the photocatalyst,enabled the photocatalyst to absorb near infrared light,and improved the photothermal conversion ability of the photocatalyst.The photothermal effect induced by Co₃O₄ increased the kinetic rate of the surface reaction,and the apparent activation energy of the reaction decreased from 43.9 k J?mol^-1 to 32.2 k J?mol^-1.The photothermal effect also increases the concentration of carriers in the photocatalyst,improving the conductivity of the photocatalyst and helping charge transport.The combination of heterojunction and photothermal effect significantly enhanced the hydrogen production performance of the photocatalyst.The hydrogen evolution performance of1%Co₃O₄@ZIS is 3.2 times that of pure ZIS,reaching 4473μmol?g^-1?h^-1.The apparent quantum efficiency of 1%Co₃O₄@ZIS is 20.2%under 420 nm monochromic light irradiation.