Gold- and Silver-Nanoparticle-Embodied Amino Acid-Based Hybrid Sustainable Hydrogel Biomatrices for the Electrocatalytic Reduction of Nitrate to Value-Added Ammonia

In this study, in situ gold and silver nanoparticle syntheses have been investigated within Fmoc-Y -OH and Fmoc-W- OH-based supramolecular hydrogel matrices to form four different hybrid hydrogel systems, which include Fmoc-Y -AuNPs, Fmoc-Y -AgNPs, Fmoc-W -AuNPs, and Fmoc-W -AgNPs for electrocatalytic nitrate reduction reaction (eNO 3 RR). The catalytic performance of the resulting hybrid xerogels has been evaluated as a function of catalyst’s loading and electrolyte’s pH. Among all these four hybrid xerogels, Fmoc-Y -AuNPs exhibited the best activity, achieving 88.8% Faradaic efficiency (FE) at −0.1 V vs RHE (pH 5). Post-catalytic FE-SEM and HR-TEM analyses confirmed the coexistence of both nanofibrillar and nanoparticle morphologies, bestowing excellent post-catalytic stabilities of the xerogel eNO 3 RR catalysts. Additionally, Fmoc-W -based AuNP and AgNP hydrogels induced apoptosis in PANC-1 cells, demonstrating their dual catalytic and bioactivity. Overall, these findings highlight aromatic amino acid-based supramolecular hydrogels as green, cost-effective, and eco-friendly templates in devising sustainable and reusable electrocatalysts for efficient nitrate reduction reactions to produce value-added, carbon-free energy carrier chemical, ammonia. Such integration of sustainable synthesis, catalytic efficiency, and biological relevance places these hybrid nanobiomaterials as a promising platform for environmental remediation and green, value-added ammonia production from agricultural waste.