Fabrication and engineering of Ru local structures toward enhanced kinetics of hydrogen generation

A strategy to boost hydrogen generation from ammonia borane hydrolysis was proposed by engineering Ru local structures via the employment of Cl-free Ru precursors and acid-leaching of the bimetallic Ru-Co catalysts. The effects of Cl and Co were separately investigated by comparing the Cl-free/Cl-containing monometallic Ru catalysts and Co-leaching/Co-containing bimetallic Ru-Co catalysts, respectively. Decoupled from the Co electronic effects (electron transfer from Co to Ru), the Cl geometric effects (site blockage and steric hindrance) were identified as the main factors, which could be further promoted by introducing more low-coordinated Ru sites. The increase of Co content gives rise to more edge-like Ru active sites after acid leaching, with a lower H2O activation barrier for hydrogen production. Consequently, al-Ru1Co with the most edge-like Ru active sites demonstrated a 4.1-fold increase in catalytic activity. The insights revealed here might guide the design and preparation of metal catalysts with the maximum active sites.