Exploiting Ru-Induced Lattice Strain in CoRu Nanoalloys for Robust Bifunctional Hydrogen Production

Designing bifunctional catalysts capable of driving the electrochemical hydrogen evolution reaction (HER) and also H₂ evolution via the hydrolysis of hydrogen storage materials such as ammonia borane (AB) is of considerable practical importance for future hydrogen economies. Herein, we systematically examined the effect of tensile lattice strain in CoRu nanoalloys supported on carbon quantum dots (CoRu/CQDs) on hydrogen generation by HER and AB hydrolysis. By varying the Ru content, the lattice parameters and Ru-induced lattice strain in the CoRu nanoalloys could be tuned. The CoRu_0.5 /CQDs catalyst with an ultra-low Ru content (1.33 wt.%) exhibited excellent catalytic activity for HER (η=18 mV at 10 mA cm^-2 in 1 M KOH) and extraordinary activity for the hydrolysis of AB with a turnover frequency of 3255.4 mol ${}_{\left(H{}_2\right)}$ mol^-1 _(Ru) min^-1 or 814.7 mol ${}_{\left(H{}_2\right)}$ mol^-1 _(cat) min^-1 at 298 K, respectively, representing one of the best activities yet reported for AB hydrolysis over a ruthenium alloy catalyst. Moreover, the CoRu_0.5 /CQDs catalyst displayed excellent stability during each reaction, including seven alternating cycles of HER and AB hydrolysis. Theoretical calculations revealed that the remarkable catalytic performance of CoRu_0.5 /CQDs resulted from the optimal alloy electronic structure realized by incorporating small amounts of Ru, which enabled fast interfacial electron transfer to intermediates, thus benefitting H₂ evolution kinetics. Results support the development of new and improved catalysts HER and AB hydrolysis.