Kinetics of NaBH4 hydrolysis on carbon-supported ruthenium catalysts

In this work, different shapes (powder and spherical) of ruthenium-active carbon catalysts (Ru/C) were prepared by impregnation reduction method for hydrogen generation (HG) from the hydrolysis reaction of the alkaline NaBH4 solution. The effects of temperature, amount of catalysts, and concentration of NaOH and NaBH4 on the hydrolysis of NaBH4 solution were investigated with different shapes of Ru/C catalysts. The results show that the HG kinetics of NaBH4 solution with the powder Ru/C catalysts is completely different from that with the spherical Ru/C catalysts. The main reason is that both mass and heat transfer play important roles during the reaction with Ru/C catalysts. The HG overall kinetic rate equations for NaBH4 hydrolysis using the powder Ru/C catalysts and the spherical catalysts are described as r = A exp (−50740/RT) [catalyst]1.05 [NaOH]−0.13 [NaBH4]−0.25 and r = A exp (−52,120/RT) [catalyst]1.00 [NaOH]−0.21 [NaBH4]0.27 respectively.

► Kinetics of NaBH4 hydrolysis on powder Ru/C and spherical Ru/C catalysts.
► NaOH has a negative effect on H2 generation (HG) rate with Ru/C catalysts.
► HG rate of powder Ru/C catalysts decreases while NaBH4 concentration increases.
► HG rate of spherical Ru/C catalysts increases at first and then decreases.
► The main reason is the competition between mass and heat transfer.