Greenly synthesized zinc oxide nanoparticles: An efficient, cost-effective catalyst for dehydrogenation of formic acid and with improved antioxidant and phyto-toxic properties

Formic acid (FA) dehydrogenation is of particular industrial interest as a source of alternative fuels such as H2. However, the development of economical, highly efficient, and selective catalysts for this reaction is a challenging task. Most highly selective catalysts for the conversion of formic acid (FA)/sodium formate (SF) system into hydrogen are based on precious noble metals. Rendering their large-scale utilization more cumbersome and expensive. Therefore, it is of utmost importance to explore a facile and cost-effective strategy for the fabrication of a simple structured solid nano-catalyst with outstanding performance and selectivity for H2 generation without CO evolution from the FA/SF system. In the current study, a phenolic-enriched extract of wild olive leaves was employed for the synthesis of ZnO nanoparticles (ZnO@WOLE-NPs). TEM analysis revealed that the size of ZnO@WOLE nanoparticles was about33 nm. Zeta potential evaluation (38.39 ± 1.32 mV) demonstrated the significant stability of the nanoparticles. XRD analysis provided insights into the formation of hexagonal wurtzite phase ZnO nanoparticles. The reaction conditions were optimized. These resulting ZnO@WOLE-NPs showed extraordinarily high catalytic performance and about 80 % selectivity for H2 generation from the FA/SF system at 50 °C. A turn over frequency and activation energy values for dehydrogenation of FA were noted as 1519 h−1 and 32.1 kJ mol−1, respectively. The kinetics and thermodynamics of FA dehydrogenation were also determined. Furthermore, ZnO@WOLE-NPs exhibited potent antioxidant activity against hydroxyl, DPPH, superoxide, and peroxide radicals. Moreover, the synthesized nanoparticles demonstrated the highest seed germination of Okra seed at a concentration of 1.25 µg mL−1. Whereas, the highest shoot length and root length were observed at the concentration of 1 µg mL−1. [Display omitted] •Green synthesis of ZnO NPs was achieved by a phenolic-enriched extract of wild olive leaves.•FTIR, TEM-EDX, UV-Vis, PXRD, DLS, and zeta potential were used to characterize ZnO NPs.•The ZnO NPs were explored for their potential as nano-catalysts for the selective dehydrogenation of formic acid.•Mechanism involved in the dehydrogenation of formic acid was also investigated.•ZnO NPs were found as efficient anti-oxidant and phyto-toxic agent.