Cotton stalk activated carbon-supported Co–Ce–B nanoparticles as efficient catalysts for hydrogen generation through hydrolysis of sodium borohydride

Abstract

Porous cotton stalk activated carbons (CSAC) were prepared by phosphoric acid activation of cotton stalks in a fluidized bed. The CSAC-supported Co–B and Co–Ce–B catalysts were prepared by the impregnation-chemical reduction method. The samples were characterized by the nitrogen adsorption, XRD, FTIR and TEM measurements. The effects of the sodium borohydride (NaBH4) and sodium hydroxide (NaOH) concentrations, reaction temperature and recyclability on the rate of NaBH4 hydrolysis over the CSAC-supported Co–Ce–B catalysts were systematically investigated. The results showed that the agglomeration of the Co–Ce–B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium. The CSAC-supported Co–Ce–B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min−1 g−1Co at 25 °C, which is higher than the most reported cobalt-based catalysts. The catalytic hydrolysis of NaBH4 was zero order with respect to the NaBH4 concentration, and the hydrogen generation rate decreased with the increase in the NaOH concentration. The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol−1. A kinetic rate equation was also proposed. Keywords: Sodium borohydride, Hydrogen, Activated carbon, Co–Ce–B catalyst, Catalytic activity, Kinetics