A hybrid synthesis protocol that combines electroless plating and the supercritical CO(2) (scCO(2)) technique is developed for the first time to decorate multi-walled carbon nanotubes (CNTs) with Ni nanoparticles. The scCO(2) fluid, which is immiscible with aqueous plating solution, renders a heterogeneous Ni deposition reaction and suppresses the lateral growth of Ni, which leads to the formation of nanoparticles. A uniform dispersion of tightly anchored particles, a few nanometers in diameter, on CNTs can be achieved. Since the electroless deposition process can be easily manipulated, large-scale production should be realizable. The constructed CNT/Ni nano-composite exhibits a synergistic property in hydrogen storage performance, which is evaluated using a high-pressure microbalance. The deposited nanoparticles enhance the hydrogen spillover reaction on CNTs, tripling the hydrogen storage amount at room temperature as compared to pristine CNTs. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.