Cobalt is a very efficient metal in catalyzing the hydrogen generation throughsolvolysis (i.e. hydrolysis and methanolysis) of boron-based complex hydrides (i.e.sodium borohydride and ammonia borane) at room conditions. To date, it has oftenshowed to be as reactive as noble metals like Ru or Pt in specific, optimized experimentalconditions. As heterogeneous catalyst, cobalt can be used as nanoparticles (pure ordoped) or, supported over supports (e.g. alumina or activated carbon) or substrates (e.g. nickel foam or copper plate). However, the nature of the catalytically active phase is asubject of debate. Throughout the sodium borohydride-dedicated literature, twocompounds, among others, have been mainly suggested to form; as a result, both arebelieved to be the catalytically active phase. The compounds are cobalt boride CoxB (withx from 1 to 3) and an alloy Co-B. In fact, sodium borohydride, which is a well knownreducing agent, has the ability to reduce any cobalt precursor to form an active catalyst.For example, such reducibility is now largely used to accelerate the formation of anactive catalyst from any cobalt precursor; the in situ formed cobalt catalyst is then used toaccelerate the hydrolysis of ammonia borane. Be that as it may, the nature of thecatalytically active cobalt phase is still unknown. And, this is the topic of the presentchapter, which is structured as follows: (i) review of the literature devoted to thereduction of cobalt cations by sodium borohydride; (ii) survey of the cobalt-basedcatalysts used in the solvolysis of sodium borohydride; (iii) discussion of the cobalt-basedcatalysts used in the solvolysis of ammonia borane; (iv) critical discussion about thenature of the in situ formed cobalt catalysts.
|Title of host publication||Cobalt: Characteristics, Compounds and Applications|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||28|
|Publication status||Published - 1 Mar 2011|
ASJC Scopus subject areas