Boric acid-assisted preparation and characterization of laurel (Laurus nobilis L.) leaves-derived activated carbon for efficient hydrogen generation via NaBH4 alcoholysis

Abstract

In this study, an active carbon-based Ln-B-900 catalyst is synthesized by a chemical activation method using boric acid as an activating agent. It is evaluated as a metal-free catalyst in the NaBH4 alcoholysis reaction. The metal-free porous carbons are prepared by pyrolysis, and the effects of various carbonization temperatures and times are investigated. The highest catalytic activity is observed for the sample carbonized at 900 degrees C for 45 min. Following this process, the specific surface area of Ln-B-900 catalyst is observed to increase from 0.80 m2g-1 to 397.6 m2/g, and the pore volume reach to 0.62 cm3/g. Boric acid promoted the formation of mesopores and micropores during the activation process, resulting in a more efficient development of the porous structure. In methanol/propylene glycol reactions carried out at 30 degrees C using Ln-B-900 catalyst, a hydrogen generation rate reaches up to 241,200 mLmin-1gcat -1 is achieved with 0.25 g NaBH4. Furthermore, the activation energy of the Ln-B-900 catalyst is calculated to be 33.20 kJ/mol over the temperature range of 20-50 degrees C. Although 100% conversion is achieved in each cycle in successive applications, only around 84% of the catalytic activity is retained by the third cycle. These results show that biochar activated with boric acid is an effective porous catalyst for hydrogen production by NaBH4 alcoholysis.