Co, Ni-based nanoparticles supported on graphitic carbon nitride nanosheets as catalysts for hydrogen generation from the hydrolysis of ammonia borane under broad-spectrum light irradiation

Abstract

From the viewpoint of tailoring the atomic and nanoscale structures of semiconductors to enhance the solar-to-hydrogen energy conversion, we employed an in-situ gas template-assisted co-polymerization route, where melamine and 2,4,6-triaminopyrimidine were co-monomers and NH4Cl was the in-situ gas template, to synthesize porous broad-spectrum light-responsive carbon nitride nanosheet (termed as CNN) species with increased π-electron availability. Then we developed CNN-supported Co and Ni nanoparticles (NPs) for catalytic hydrogen generation from aqueous ammonia borane (NH3BH3) under light irradiation (λ ≥ 420 nm) at room temperature. Though all the Co-based catalysts had the similar activities with total turnover frequency (TOF) values of 37.5–44.1 min−1 in the dark, they exhibited significantly different and enhanced photocatalytic activities. Remarkably, the optimized catalyst had a total TOF value of 123.2 min−1, exceeding the values of reported non-noble metal catalysts. Moreover, the porous CNN species possessed the C-substitution for N, tunable narrow bandgaps of 0.71–2.34 eV and efficient separation of photogenerated charge carriers. This resulted in the enriched electron density of metal NPs and the apparent quantum yield of 66.9% at 420 nm.