Chiral plasmonic nanocatalysts for enhanced CO₂ methanation activity and selectivity via polarized photogenerated hot carriers

Chiral plasmonic nanocatalysts provide a unique platform for controlling the product selectivity in photocatalytic reactions. In this study, we synthesized highly stable chiral plasmonic photocatalysts by integrating helical plasmonic nanorods (HPNRs) as the core with a mesoporous silica (m-SiO₂) layer as the shell. These nanocatalysts demonstrated exceptional chiroptical properties and a strong response to circularly polarized light (CPL), enabling selective and efficient photocatalysis. Under light irradiation in the presence of water vapor, carbon dioxide (CO₂) was effectively reduced to methane (CH₄) using the HPNR-based photocatalysts. Notably, HPNR@SiO₂ catalysts achieved efficient CO₂-to-CH₄ conversion with 2.4-fold higher CH₄ production under chirality-matched CPL (1.64 vs. 0.70 μmol·h⁻¹·g⁻¹) and electron selectivity exceeding 95%. This enhancement in methanation efficiency is attributed to the asymmetric generation of hot electrons on the chiral surface, which facilitates the 8-electron transfer required to convert adsorbed CO₂ to CH₄, as corroborated by photoelectrochemical measurements and platinum photodeposition experiments. Our work not only expands the knowledge of chiral photocatalysts but also demonstrates the potential of CPL in improving the efficiency and selectivity of CO₂ conversion, which is a critical challenge in the field of sustainable energy and environmental treatment.