Nature-Inspired Ag-Decorated CoAlLa-LDH/TiO₂ S-Scheme Photocatalysts for Efficient CO₂ Reduction to CO and CH₄

A bioinspired methodology for synthesizing silver nanoparticles (Ag-NPs) is developed by harnessing extracts from Nephelium lappaceum (Rambutan) leaves as a natural reducing agent, thereby eliminating the need for conventional toxic reductants. The synthesized Ag-NPs, leveraging their strong localized surface plasmon resonance (LSPR) effect, are integrated into a hybrid photocatalyst comprising a trimetallic vacancy-rich CoAlLa layered double hydroxide (LDH) and TiO₂, forming an S-scheme heterojunction. Under optimized conditions (3 wt% Ag loading on a 10 wt% CoAlLa-LDH/TiO₂ framework), the photocatalyst achieves CO and CH₄ generation rates of 95.63 and 13.80 μmol g⁻¹ h⁻¹ with 3.62- and 4.33-fold enhancement over pristine TiO₂, respectively. A strong contact between the trimetallic TiO₂ and CoAlLa-LDH with the formation distinct S-scheme heterojunction provides pathways to proficiently enhance the photocatalytic induced electron/hole pairs separation. The incorporation of Ag further improves the separation of electron/hole pairs due to the LSPR effect and works as an electron reservoir for electrons and an active hotspot for photoreaction on its surface toward CO₂ reduction. The recyclability assessments confirm the structural integrity and catalytic efficacy of the nanocomposite over successive cycles. This work demonstrates the viability of green nanoparticle synthesis, innovative heterojunction design and contributes to the advancement of clean fuel production.