Low-cost CuNi-CeO2/rGO as an efficient catalyst for hydrolysis of ammonia borane and tandem reduction of 4-nitrophenol

Abstract

Low-cost metallic nanoparticles as catalysts with good performance are highly desired for the development of hydrogen storage materials. In this work, ceria-doped CuNi nanoparticles were successfully immobilized on the surfaces of reduced graphene oxide (rGO) by a simple co-reduction approach in aqueous solution at room temperature, characterized by ICP-OES, XRD, TEM, SEM-EDS and XPS techniques. The as-synthesized CuNi-CeO2/rGO nanocomposites with various metal contents had been employed as heterogeneous catalysts for the hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB) under mild conditions. The optimal catalyst of Cu0.8Ni0.2-CeO2/rGO with CeO2 content of 13.9 mol% exhibited an excellent catalytic activity with the exceedingly high TOF value of 34.4·molH2·molcatalyst−1·min−1 at 298 K. The apparent activation energy was calculated to be 19.1 kJ mol−1, even lower than most of noble-metal-based catalysts for AB dehydrogenation. The detailed kinetics of AB hydrolysis catalyzed by Cu0.8Ni0.2-CeO2/rGO had been investigated on different concentrations of catalyst, substrate and temperatures. Moreover, the obtained in situ hydrogen from AB hydrolysis can be further applied to reduce 4-nitrophenol with a high TOF value of 8.1 min−1 at room temperature. The high catalytic activity of Cu0.8Ni0.2-CeO2/rGO would be contributed to the small size of CuNi-CeO2 NPs, metal-metal synergy, and the metal-support interaction.