Green-synthesized Co@VHE nanocatalyst from Verbascum insulare for enhanced hydrogen generation and biological applications

Abstract

In this study, a novel multifunctional material was synthesized by decorating the hydrothermal extract obtained from Verbascum insulare Boiss. & Heldr (VHE) with metallic cobalt nanoclusters (Co@VHE) via in situ reduction using sodium borohydride (NaBH<inf>4</inf>). The material was first evaluated for its biological activity, including antimicrobial and antioxidant properties. While VHE exhibited antifungal activity only against Y. lipolytica, Co@VHE demonstrated broad-spectrum antimicrobial activity, with the highest zone of inhibition against B. subtilis (26.67 ± 1.16 mm). Co@VHE also exhibited superior antioxidant capacity, showing the strongest DPPH radical scavenging activity (IC<inf>50</inf>: 4.30). LC-MS/MS analysis confirmed the presence of quinic acid and protocatechuic acid in Vrb-1, along with 17 phenolic compounds in VHE. Additionally, Co@VHE's catalytic performance was evaluated for hydrogen generation through sodium borohydride (NaBH<inf>4</inf>) hydrolysis. Under optimal conditions (7.5 % NaOH, 15 mg catalyst, 3 % NaBH<inf>4</inf>), a successful hydrogen generation rate of 36,624 mL g−1 min−1 was achieved. Kinetic and reusability studies further demonstrated the material's high efficiency, moderate activation energy (55 kJ mol−1), and excellent stability over six cycles. Comparative analysis revealed that Co@VHE outperformed several previously reported synthetic cobalt-based catalysts. This work not only introduces V. insulare extract as an effective and eco-friendly catalyst support for the first time, but also highlights its multifunctional potential in both biomedical and energy applications. © 2025 Elsevier B.V., All rights reserved.