Composition-controlled catalysis of reduced graphene oxide supported CuPd alloy nanoparticles in the hydrolytic dehydrogenation of ammonia borane

• Composition-controlled synthesis of CuPd alloy nanoparticles.
• Reduced graphene oxide (RGO) was used as the catalyst support.
• Hydrogen generation from the hydrolysis of ammonia borane (AB).
• The highest activity was obtained by RGO-Cu75Pd25 catalysts in the hydrolysis of AB.
• An initial TOF of 29.9 min−1 was obtained by annealed-RGO-Cu75Pd25 catalysts.

Addressed herein is the composition-controlled catalysis of CuPd alloy nanoparticles (NPs) supported on reduced graphene oxide (RGO) in the hydrolytic dehydrogenation of ammonia borane (AB). Nearly monodisperse CuPd alloy NPs were synthesized by using a surfactant-assisted organic solution phase protocol comprising the co-reduction of acetylacetonate complexes of Pd and Cu by morpholine borane complex in oleylamine and 1-octadecene at 80 °C. The presented recipe allowed us to make a composition control over the CuPd alloy NPs. Three different compositions of CuPd alloy NPs (2.7 nm Cu30Pd70, 2.9 nm Cu48Pd52, 3.0 nm Cu75Pd25) could be prepared among which the Cu75Pd25 NPs showed the best catalytic performance in hydrogen generation from the hydrolysis of AB. Among the various support materials tested for as-prepared Cu75Pd25 alloy NPs, the RGO-Cu75Pd25 catalysts showed the highest performance in the hydrolysis of AB. Moreover, the activity of the RGO-Cu75Pd25 catalysts were dramatically enhanced by annealing them at 400 °C for 1 h under Ar–H2 (5% H2) gas flow and an unprecedented TOF value of 29.9 min−1 was obtained in the hydrolysis of AB at room temperature. The reported TOF value here is much higher than RGO-Cu (TOF = 3.61 min−1) and even higher than RGO-Pd catalysts (TOF = 26.6 min−1). The detailed kinetics of RGO-Cu75Pd25 catalyzed AB hydrolysis was also studied depending on catalyst concentration, substrate concentration and temperature. The apparent activation energy of the catalytic hydrolysis of AB was calculated to be 45 ± 3 kJ mol−1.

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