Ruthenium supported on ZIF-67 as an enhanced catalyst for hydrogen generation from hydrolysis of sodium borohydride

H-2 generation (HG) from NaBH4 hydrolysis represents as a safe, mild and convenient method for storing and releasing H-2. As Ru is the most effective metal for catalyzing NaBH4 hydrolysis, continuous efforts are being made to find suitable supports for immobilizing Ru nanoparticles (NPs) to form heterogeneous Ru catalysts. Since NaBH4 hydrolysis typically occurs in water and at high temperature, an ideal support necessitates high stability in water, high surface area, hierarchical structures and even synergy with Ru. In this study, ZIF-67 is particularly selected as a catalytic active support for immobilizing Ru species because ZIF-67 has proven to be highly stable in water and also hierarchically consists of Co, another catalytic active component for HG from NaBH4 hydrolysis. Compared to ZIF-8, ZIF-67 is validated to catalyze NaBH4 hydrolysis for HG, making Ru/ZIF67 an enhanced Ru-based catalyst. Ru/ZIF also exhibited a higher catalytic activity than the equivalent Ru species, suggesting that the supporting of Ru on ZIF-67 enhanced catalytic activities of Ru species. As the effect of Ru loading on Ru/ZIF was evaluated, a higher Ru loading significantly boosted catalytic activities by substantially reducing E-a. HG from Ru/ZIF-catalyzed hydrolysis of NaBH4 could be optimized in the presence of 7.5 wt% of NaOH to exhibit a low E-a of 36.4 kJ mol(-1), which is much lower than most of reported Ru-based catalysts. In addition, Ru/ZIF can be also re-used with consistent catalytic activities without regeneration. These results validate that Ru/ZIF67 composite is a promising and effective catalyst for H-2 production from NaBH4 hydrolysis.