Radiofrequency argon plasma has been used for cobalt-boron surface modification. The argon plasma treatments enhance the cobalt-boron reactivity in hydrolysis of NaBH4 to release H-2. The improved activity for cobalt-boron after plasma treatment is attributed to the enhanced synergistic effect between cobalt and boron and the large specific surface area resulting from the mesopores formed on the surface during the treatment. The synergistic effect, pore size and pore volume of cobalt-boron can be adjusted by changing either the plasma power and time or the argon pressure. High plasma power was found to cause the decomposition of cobalt-boron. Argon plasma treatment also improved the cycle performance of Co-B alloy in the hydrolysis of NaBH4 to release H-2.