Enhanced charge separation by continuous homojunction with spatially separated redox sites for hydrogen evolution

Photocatalytic hydrogen generation represents a promising strategy for the establishment of a sustainable and environmentally friendly energy reservoir. However, the current solar-to-hydrogen conversion efficiency is not yet sufficient for practical hydrogen production, highlighting the need for further research and development. Here, we report the synthesis of a Sn-doped TiO₂ continuous homojunction hollow sphere, achieved through controlled calcination time. The incorporation of a gradient doping profile has been demonstrated to generate a gradient in the band edge energy, facilitating carrier orientation migration. Furthermore, the hollow sphere’s outer and inner sides provide spatially separated reaction sites allowing for the separate acceptance of holes and electrons, which enables the rapid utilization of carriers after separation. As a result, the hollow sphere TiO₂ with gradient Sn doping exhibits a significantly increased hydrogen production rate of 20.1 mmol·g⁻¹·h⁻¹. This study offers a compelling and effective approach to the designing and fabricating highly efficient nanostructured photocatalysts for solar energy conversion applications.