Sulfur poisoning-resistant TiO2/Cu-doped ZnIn2S4 photoanode for achieving efficient sulfur oxidation

Abstract

Ternary ZnIn2S4 is a layered metal sulfide and suitable for catalyzing H2S-containing industrial waste streams due to its excellent light absorption in the visible region. However, imperfect electrical conductivity and slow surface reaction lead to severe internal intrinsic charge recombination. For this reason, we modify pristine ZnIn2S4 by synergistic coordination of heterojunction and doping. The TiO2/0.6 ml Cu2+-ZIS sample achieves a photocurrent density of 2.87 mA/cm2, which is 8.2 times higher than that of pure ZnIn2S4. Investigation of the surface states (SS) shows that the improved performance results from an increase in the density of available surface states as well as the consistency of the surface state center potential with the S/H2S oxidation potential. This is the new attempt to analyze the photoelectrocatalytic (PEC) behavior of the sulfur oxidation reaction using surface state theory. The results of catalytic product resolution and data from theoretical calculations indicate that the timely desorption of polysulfide ions at Cu2+ sites and the solubility of the only oxidation product (S2O32-), are the reasons for maintaining high performance after 4 h stability testing. This study not only gives a new reference for the modification strategy of ZnIn2S4 but also a new solution for catalyst S poisoning.