Morphology control and phase transformation of ZIS/TiO₂ into CdSe(en)_0.5/CIS/TiO₂ photoanode for enhanced solar hydrogen generation

An inorganic–organic CdSe(en)_0.5/CdIn₂S₄/TiO₂ complex heterostructure was successfully synthesized using a facile solvothermal method. The morphology of a CdSe(en)_0.5/CdIn₂S₄/TiO₂ heterostructure was controlled by varying the concentrations of cadmium nitrate and selenium precursors in ethylenediamine. Intentionally controlling the morphology enhances the absorption within the visible region compared to a ZnIn₂S₄/TiO₂ photoanode. The photoelectrochemical (PEC) study shows that the CdSe(en)_0.5/CdIn₂S₄/TiO₂ photoanode complex heterostructure exhibits a photocurrent density of 2.43 mA cm⁻² at 0 V versus Ag/AgCl, which is 180% higher than that of a ZnIn₂S₄/TiO₂ photoanode. The extra-delayed lifetime and photostability of CdSe(en)_0.5/CdIn₂S₄/TiO₂ complex heterojunction is cause of efficient hole scavenging. During the PEC measurement, the Se and ethylenediamine leaches out into the electrolyte while S²⁻ from the Na₂S + Na₂SO₃ electrolyte reacts with surface of the CdSe(en)_0.5/CdIn₂S₄/TiO₂ complex heterojunction. Such structure can effectively separate the charge carrier and yields 100 µmol of hydrogen within 3 h. The possible charge transfer mechanism during solar hydrogen generation in an inorganic–organic CdSe(en)_0.5/CdIn₂S₄/TiO₂ complex heterojunction structure has also been proposed.