Structural and compositional analysis of Co-based coatings after catalytic tests for the sodium borohydride hydrolysis

Abstract

The use of Co-based catalysts for the sodium borohydride hydrolysis for hydrogen production is a well-known process as a source of clean energy, although its mechanisms are still under discussion. With the aim of acquiring a deeper knowledge about this catalytic process, three different catalysts (Co, CoC and CoB) were deposited as a thin film layer by magnetron sputtering onto a polymeric membrane, used as a substrate and analyzed by advance transmission and scanning-transmission electron microscopy techniques (STEM). Structural and compositional characterizations, by electron energy loss spectroscopy (EELS), have been performed on the coatings before and after their use as catalysts on the sodium borohydride reaction for 90 min, to check the production of hydrogen. Results have shown the formation of CoxB nanoflakes and other Co-based compounds over the catalysts and related to their catalytic activity. Knowing the changes in the structure and composition of the catalysts is key to understanding their catalytic behavior, activity and durability. Among the analyzed catalysts, the Co–C presents better activity during the first cycles, which is related to a larger formation of CoxB.