Polyol-Intermediated Facile Synthesis of B-Site-Rich Ru-Based Nanocatalysts for CO-Free Hydrogen Production via Ammonia Decomposition.

Herein, a B-site-rich Ru/MgAlO nanocatalyst for the production of CO-free hydrogen from ammonia (NH) is synthesized using the polyol method. The polyol method enables size-sensitive Ru-nanoparticle growth and controlled B-site formation on the catalyst by tuning the carbon-chain length of the polyol solvent used, obviating the use of a separate stabilizer and enhancing electron donation from Ru (with a high surface electron density) and π-back bonding. The Ru/MgAlO (BG) catalyst synthesized using butylene glycol (a long-carbon-chain solvent) contains 2.5 nm Ru particles uniformly dispersed on its surface and abundant B sites at (0 0 2)/(0 1 1). Moreover, the Ru/MgAlO (BG) catalyst exhibits lower activation energy (48.9 kJ mol) and higher H formation rate (565-1,236 mmol g h at 350-450 °C and a weight hourly space velocity of 30,000 mL g h) during the NH decomposition reaction than catalysts with a similar Ru particle size and high metal dispersion synthesized by the impregnation and deposition-precipitation methods. This high performance is possibly because the abundant electron-donating B sites on the catalyst surface accelerate the recombination-desorption of N, which is the rate-determining step of the NH decomposition reaction at low temperatures. Thus, this study facilitates clean hydrogen production.