Ultrasound-excited hydrogen radical from NiFe layered double hydroxide for preparation of ultrafine supported Ru nanocatalysts in hydrogen storage of N-ethylcarbazole

Highly active Ru nanoparticles (Ru NPs) supported on NiFe layered double hydroxide (Ru/NiFe-LDH) are prepared easily using ultrasound-assisted reduction method without chemical reductants and stabilizers. The plentiful hydroxyls on NiFe-LDH are excited into hydrogen radicals (•H) under the action of ultrasound for reducing Ru(3+) to Ru(0). Ru NPs with an average particle size of 1.26 nm highly disperse on the mesopore-like surface of NiFe-LDH, which improve the catalytic performance for N-ethylcarbazole (NEC) hydrogenation. The experimental results show that 5Ru/NiFe-LDH-300–60 exhibits the best catalytic performance with 100% conversion of NEC, 98.88% yield of dodecahydro-N-ethylcarbazole (12H-NEC) and 5.77 wt% mass hydrogen storage capacity under the reaction conditions of 110 ℃, 6 MPa and m(Ru):m(NEC) = 0.15 wt% for 80 min. The kinetics study shows that the apparent activation energy is only 25.15 kJ/mol, which is the lowest in the reported literatures. Ru complexes with O-contained groups on NiFe-LDH, improving the catalytic stability in NEC hydrogenation.