Porous nitrogen-doped carbon-immobilized bimetallic nanoparticles as highly efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

Two N-doped carbon materials, N-doped Vulcan XC-72 carbon labelled as NXC and graphite carbon nitride labelled as C3N4, were selected as supports to prepare a series of bimetallic AuM (M = Co, Ni) nanoparticles (NPs) using three different reduction ways towards mixed metal ions AuCl4- and M2+, and then the as-synthesized supported bimetallic AuM NPs were used as catalysts for hydrolytic dehydrogenation of ammonia borane (NH3BH3). All the catalysts exhibited high dispersion and small size of bimetallic NPs; however, they exhibited remarkably different catalytic activities featuring total turnover frequency (TOF) values from 6.4 to 42.1 mol(H2) mol(cat)(-1) min(-1). Among all the catalysts, the NXC-immobilized AuCo NPs through in situ synthesis using NaBH4 and NH3BH3 as reductants exhibited the highest activity with a total TOF value of 42.1 mol(H2) mol(cat)(-1) min(-1), which was among the highest values for Co-based catalysts ever reported for hydrolytic dehydrogenation of NH3BH3. This remarkably enhanced activity may be attributed to the synergistic effect of the N-doped NXC support and AuCo NPs and the resulting highly efficient activation of N-B bond in NH3BH3. In addition, the AuCo catalysts showed good recyclability, demonstrating that they had high stability/durability.