One-step synthesis of reduced graphene oxide supported CoW nanoparticles as efficient catalysts for hydrogen generation from NH3BH3

Abstract

W-doped Co nanoparticles (NPs) supported on reduced graphene oxide (RGO) were prepared by the one-step in situ co-reduction of an aqueous solution of cobalt(II) chloride, sodium tungstate dihydrate, and graphene oxide (GO) using NaBH4 as the sole reductant at room temperature. The structure, size, and composition of the CoW/RGO catalysts were characterized by powder XRD, FTIR, EDS, and TEM. The as-synthesized Co0.9W0.1/RGO catalysts exhibited good catalytic activity for the hydrolytic dehydrogenation of ammonia borane (AB) at room temperature. Co/RGO, W/RGO, RGO-free Co0.9W0.1, and Co0.9W0.1/RGO catalyst had a turnover frequency (TOF) of 3.0, 0.1, 1.2, 16.4 mol H2 (mol catalyst)−1 min−1 at 25 °C. Compared to Co/RGO, W/RGO, and the RGO-free Co0.9W0.1, the as-synthesized Co0.9W0.1/RGO nanocatalysts exhibited much better catalytic activity. In addition, kinetic studies indicated that the catalytic hydrolysis of AB by Co0.9W0.1/RGO shows zeroth order kinetics with respect to the substrate concentration, but first order kinetics with respect to the catalyst concentration. Furthermore, the activation energy (Ea) of Co0.9W0.1/RGO was estimated to be 30.7 kJ mol−1, which is lower than the values of most reported metal-based catalysts.