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

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 broadspectrum light-responsive carbon nitride nanosheet (termed as CNN) species with increased pi-electron availability. Then we developed CNN-supported Co and Ni nanoparticles (NPs) for catalytic hydrogen generation from aqueous ammonia borane (NH3BH3) under light irradiation (lambda >= 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. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.