Ion exchange resin supported cobalt boride as highly efficient catalyst for the hydrolysis of a concentrated alkaline stabilized sodium borohydride solution: A catalyst de-/reactivation study

The performance, reusability and regeneration of a gel type strong acid ion exchange resin supported cobalt boride catalyst for the hydrolysis of a concentrated alkaline stabilized NaBH4 solution (10 wt% NaBH4, 5 wt% NaOH) at 60 °C was investigated. The catalyst molar Co/B-ratio pointed towards the presence of both metallic Co and Co2B. Its activity in terms of initial hydrogen generation rate amounted 31.1 L/(gCo2B min). The catalyst, however, suffered from activity loss over 10 consecutive runs. Deactivation experiments and related catalyst characterization (ICP, HAADF-STEM-EDX and XPS) demonstrated that the active Co2B was oxidized by NaOH to Co(OH)2 and NaB(OH)4. The deactivated catalyst was regenerated with a 0.04 M hydrochloric concentration, even increasing the initial catalytic activity. This was also confirmed by the presence of metallic Co, Co2B and Co(OH)2 in the catalyst. Furthermore, the support did not only stabilize these Co compounds: its ion exchange function was also necessary to stabilize the Co2+ formed by the regeneration.