Facile fabrication of large-area hierarchical plasmonic cavities with broadband plasmon resonance for enhanced photocatalytic hydrogen evolution

Integrating hierarchical plasmonic cavities into photocatalysis offers a promising avenue for expanding the light utilization range to cover the entire solar spectrum. However, fabricating these nanostructures with seamless size transitions for a wide plasmon resonant range remains technically challenging, requiring precise nanofabrication control and often relying on expensive and laborious techniques like e-beam lithography and reactive ion etching. Herein, a one-step forming strategy was explored to fabricate simple yet hierarchical plasmonic cavities featuring the surface nanodome array-integrated plasmonic Fabry–Pérot cavity through a facile large-area nanoimprinting method. This design leverages a uniform feature size and periodic arrangement to broaden the light utilization range of TiO₂ across the entire solar spectrum (200–2500 nm). It consists of an upper nanodome array cavity with vertically continuous graded sizes for broadband absorption (200–1500 nm), coupled with a bottom plate cavity that enlarges the overall cavity size to extend the range to 2500 nm. Remarkably, simply adjusting the thickness of the plate cavity can tune the resonant position, eliminating the need for expensive mold modifications. When combined with TiO₂, this hierarchical plasmonic cavity significantly enhances the photocatalytic hydrogen evolution rate to 36.3 µmol/h, achieving a remarkable 9.8-fold increase compared to pure TiO₂ under full-spectrum illumination. This approach offers a convenient and inexpensive alternative to sophisticated nanofabrication techniques for large-area hierarchical plasmonic cavities with broadband plasmon resonance to enhance the photocatalytic hydrogen evolution.