Polyol‐Intermediated Facile Synthesis of B5‐Site‐Rich Ru‐Based Nanocatalysts for COx‐Free Hydrogen Production via Ammonia Decomposition

Abstract Herein, a B 5 ‐site‐rich Ru/MgAl 2 O 4 nanocatalyst for the production of CO x ‐free hydrogen from ammonia (NH 3 ) is synthesized using the polyol method. The polyol method enables size‐sensitive Ru‐nanoparticle growth and controlled B 5 ‐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/MgAl 2 O 4 (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 5 sites at (0 0 2)/(0 1 1). Moreover, the Ru/MgAl 2 O 4 (BG) catalyst exhibits lower activation energy (48.9 kJ mol −1 ) and higher H 2 formation rate (565–1,236 mmol g cat −1 h −1 at 350−450 °C and a weight hourly space velocity of 30,000 mL g cat −1 h −1 ) during the NH 3 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 5 sites on the catalyst surface accelerate the recombination–desorption of N 2 , which is the rate‐determining step of the NH 3 decomposition reaction at low temperatures. Thus, this study facilitates clean hydrogen production.