Carbon supported bimetallic Ru-Co catalysts for H2production through NaBH4and NH3BH3hydrolysis

This work investigates the effect of the addition of small amounts of Ru (0.5-1 wt%) to carbon supported Co (10 wt%) catalysts towards both NaBH4and NH3BH3hydrolysis for H2production. In the sodium borohydride hydrolysis, the activity of Ru-Co/carbon catalysts was sensibly higher than the sum of the activities of corresponding monometallic samples, whereas for the ammonia borane hydrolysis, the positive effect of Ru-Co systems with regard to catalytic activity was less evident. The performances of Ru-Co bimetallic catalysts correlated with the occurrence of an interaction between Ru and Co species resulting in the formation of smaller ruthenium and cobalt oxide particles with a more homogeneous dispersion on the carbon support. It was proposed that Ru°, formed during the reduction step of the Ru-Co catalysts, favors the H2activation, thus enhancing the reduction degree of the cobalt precursor and the number of Co nucleation centers. A subsequent reduction of cobalt and ruthenium species also occurs in the hydride reaction medium, and therefore the state of the catalyst before the catalytic experiment determines the state of the active phase formed in situ. The different relative reactivity of the Ru and Co active species towards the two investigated reactions accounted for the different behavior towards NaBH4and NH3BH3hydrolysis.