A 3D hierarchical TiO₂/CaIn₂S₄/C₃N₄ arrays photoanode with dual-heterojunction for enhanced photoelectrochemical performance

Abstract A novel 3D hierarchical TiO₂/CaIn₂S₄/C₃N₄ arrays with dual heterojunctions photoanode is constructed by stepwise deposition of CaIn₂S₄ nanosheets and ultrathin C₃N₄ onto the well-aligned TiO₂ nanorods arrays. Integrating the merit of the superior ability of CaIn₂S₄ and C₃N₄ to harvest visible light, dual type-Ⅱ heterojunction band structure and one-dimensional ordered nanostructures, the TiO₂/CaIn₂S₄/C₃N₄ photoanode exhibits simultaneous significant improvements in visible-light harvesting, charge separation and electron transfer capability. At 1.23 V (versus reversible hydrogen electrode) under AM 1.5 G irradiation, the TiO₂/CaIn₂S₄75/C₃N₄ photoanode exhibits a photocurrent density of 4.5 mA cm⁻², which is 5.2 and 51.1-fold higher than that of TiO₂/CaIn₂S₄75 and pristine TiO₂ photoanode, respectively. Moreover, the applied bias photo-to-current efficiency (ABPE) of the TiO₂/CaIn₂S₄75/C₃N₄ photoanode reaches 3.5% at 0.36 V (versus reversible hydrogen electrode). These results are helpful for fabricating more efficient heterostructure photoelectrodes.