Space confined synthesis of highly dispersed bimetallic CoCu nanoparticles as effective catalysts for ammonia borane dehydrogenation and 4-nitrophenol reduction

Abstract

Bimetallic CoCu nanoparticles (NPs) are successfully embedded within the cage-type mesopores of COOH functionalized mesoporous silica SBA-16 by double agent chemical reduction method. The presence of the COOH groups in SBA-16 control the size and dispersion of the CoCu NPs. CoCu@S16LC-20 is used as the catalyst for the hydrolysis of ammonia borane (AB) and reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The catalytic activity of the CoCu@S16LC-20 outperforms that of monometallic counterparts Co and Cu. In particular, Co40Cu60@ S16LC-20 can release H2 at a rate of 6570 mL min−1 g−1 and reveals superb catalytic activity with a turn over frequency (TOF) of 16.36 mol H2 min−1 molcatalyst−1. The superior catalytic activity of the bimetallic CoCu@S16LC-20 could be ascribed to the strong synergistic effects emerging from the modified electronic structure, smaller particle size, and 3-dimensional (3D) mesoporous silica support. The smaller particle size renders more active sites, and the mesoporous silica support provides easier paths for transfer of reactants to the catalyst. The catalyst magnetic nature permits straightforward recovery from the aqueous solution after reaction completion which enhances the reusability. The bimetallic Co40Cu60@S16LC-20 can degrade 4-NP to 4-AP at rapid rate of 3.85 × 10−2 s−1 in presence of reducing agent NaBH4.