A {Αg Plasmonic Film}/{FeL@SiO₂ Catalyst} Hybrid as an Integrated Photoplasmonic Booster of H₂ Production by HCOOH

Plasmon-assisted molecular catalysis (PAMC) is a novel phenomenon offering new tools for green H₂ production via formic acid dehydrogenation (FADH). Herein, we introduce the all-solid-state PAMC concept, where plasmonic films are used to boost FADH/H₂ catalysis by heterogeneous molecular catalysts. An integrated {Ag@SiO₂ plasmonic film}/{FeL@SiO₂ catalyst} system has been developed, in which a Fe catalyst was immobilized on SiO₂ particles and Ag@SiO₂ core-shell photoplasmonics were embedded in a film. Using flame spray pyrolysis (FSP) technology, a library of Ag@SiO₂ films with a controlled thickness D in the range of 1.5-12 μm has been engineered. The integrated {Ag@SiO₂ plasmonic film}/{FeL@SiO₂ catalyst} hybrid was optimized as an efficient photoplasmonic booster of H₂ production by HCOOH, achieving a >450% enhancement of the H₂ production rate by the FeL@SiO₂ catalyst. Under selective photoplasmonic 405 nm LED excitation, we found that the Ag@SiO₂ film thickness is the key determinant to achieve significant H₂/FADH boosting. The optimal D was 2 μm, which allowed a photoplasmonic boost of up to 440%, corresponding to a maximum H₂ production rate of 7.4 mL min^-1 (μmol of Fe catalyst)^-1. The thermodynamic basis of this phenomenon is exemplified via an Arrhenius study, revealing that the Ag@SiO₂ plasmonic film can decrease the activation energy (E_a) by 74% under 405 nm illumination. Αnalysis of the chemical basis of the phenomenon (via study of the solution potential (E_h)) reveals a significant contribution from photoplasmonic hot carriers generated by the Ag@SiO₂ film to be the key factor boosting H₂/FADH. These findings demonstrate the strong potential of integrated all-solid-state PAMC systems to deliver efficient, scalable, and light-responsive H₂ production technologies based on earth-abundant Fe catalysts and HCOOH as a commodity liquid hydrogen carrier.