Desirable performance and mechanism of RuPd nanoalloys in catalyzing hydrolytic dehydrogenation of NH3BH3

The dehydrogenation of liquid-phase chemical hydrogen storage materials (such as ammonia borane, AB, NH3BH3) is a promising strategy to develop the promising hydrogen economy. Considering that the self-hydrolysis of AB is nearly impossible at room temperature, it is very worthwhile to search a robust catalyst for this hydrolytic reaction and clarify the catalytic mechanism. In this work, a glucose-derived N/O co-doped and multi-level porous carbon (marked as g-pC, SBET = 1356 m2 g-1, Vtotal = 0.762 cm3 g-1, Smicro = 1079 m2 g-1, Vmicro = 0.427 cm3 g-1) is prepared for confining RuPd alloys. Benefitting from the positive effect of g-pC (such as the particular anchoring and geometric effects on highly and tightly confining RuPd nanoparticles, as well as enhanced hydrophilicity) and the exceptional metal alloy effect, the obtained bimetallic catalysts unveil drastically enhanced catalytic activity in AB hydrolysis compared to the monometallic counterparts. Especially, catalyzed by the optimal Ru0.25Pd0.75@g-pC with a mean alloy size of 1.5 nm (10 mg), the dehydrogenation of 1.00 mmol AB can be finished within 1 min at 303 K in NaOH solution (1.5 M). The corresponding turnover frequency and hydrogen generation rate are calculated to be 541.09 min-1 and 145950 mL min-1 g-1, respectively. Moreover, about 62% of the initial catalytic activity is still retained even in the 18th cyclic experiment, suggesting the extraordinarily long durability. In addition, the isotopic analyses present a kinetic isotope effect (KIE) of 3.38, further confirming that the scission of an O-H bond in H2O is the rate-controlling step in this hydrolytic reaction. Our work offers a competitive metal alloy catalyst for generating hydrogen from AB aqueous solution and promote the development and safety utilization of hydrogen energy.