Cobalt sandwich-stabilized rhodium nanocatalysts for ammonia borane and tetrahydroxydiboron hydrolysis

Abstract

Evolution of H2 upon catalytic hydrolysis of inorganic hydrides is a key method for clean energy production. Here, a new organocobalt precursor is used to generate nanocatalysts that are efficient, stable and recyclable. The cobalt complexes [Co(η5-C5H5)(η4-C5H6)], 1, and [Co(η5-C5Me5)(η4-C5H6)], 2, are used to reduce late transition metal chlorides to a series of late transition metal nanoparticles, abbreviated TMNP and TMNP*, respectively, that catalyse hydrolysis of B2(OH)4 and ammonia borane (AB). Among the prepared TMNP and TMNP*, the latter are found to be the most efficient and recyclable catalysts, showing, with RhNP*, TOFs of 1364 molH2 molcat−1 min−1 in B2(OH)4 hydrolysis and 125 molH2 molcat−1 min−1 in AB hydrolysis at a low catalyst loading of 0.2 mol%. The kinetic study including kinetic isotope effect leads to a proposed mechanism of the RhNP*-catalysed AB hydrolysis involving water O-H bond oxidative addition on the catalyst surface as the rate-limiting step for H2 generation.