Cobalt-based catalysts for the hydrolysis of NaBH4 and NH3BH3

Cobalt has been widely used as the main component of catalysts for the hydrolysis of sodium borohydride NaBH4 and, to a lesser extent, for the hydrolysis of ammonia borane NH3BH3. Though active in these reactions, the cobalt-based catalyst generally suffers from rapid deactivation. As emphasized in a perspective paper finalized in 2009 [Phys. Chem. Chem. Phys., 2010, 12, 14651], the nature of the catalytically active phase and the reasons for its deactivation are rather unknown. However, since 2010, significant advances have been reported. Therefore, after 4 years of fruitful research, the present perspective paper aims to (i) answer the questions asked in our previous contribution, (ii) give an overview of the new insights, and (iii) identify the nature of the catalytically active phase of cobalt. The literature of the period 2010-2013 has been exhaustively surveyed while paying attention to the characterization results and problems, the experimental conditions, and the authors' interpretations. Our main observation is that the research groups involved in the field have shown scientific curiosity and dynamism, and demonstrated ingenuity to circumvent the characterization difficulties. Thus, each group has contributed to highlight the nature of the catalytically active phase of cobalt as well as the reasons for its deactivation.