Boosting the on-demand hydrogen generation from aqueous ammonia borane by the visible-light-driven synergistic electron effect in antenna- reactor-type catalysts with plasmonic copper spheres and noble-metal-free nanoparticles

To tailor the electronic behavior of catalytically active species in heterogeneous catalysts is beneficial for regulating their catalytic performance in various reaction including hydrogen generation. Herein, we rationally synthesize a series of antenna-reactor-type catalysts with the combination of plasmonic Cu spheres (55, 130, 190, 270 and 440 nm) with catalytically active Co or Ni nanoparticles (NPs), which are used for hydrogen generation from aqueous ammonia borane (NH3BH3) at 298 K. All the catalysts show the higher activities under visible light irradiation than in the dark and the optimal Co-based catalyst has the highest room-temperature photocatalytic activity with the total turnover frequency (TOF) value of 164.8 min(-1), which outperforms the values of all the reported non-noble metal catalysts. The capture of photogenerated electrons, the monochromatic light-dependent activity and hydrogen generation of different catalysts verify that there exists the visible light-driven synergistic electron effect bewteen plasmonic Cu spheres with energetic electrons and Co NPs with excited electrons generated by interband transitions. This leads to the electron density enrichment of Co NPs and the resultantly enhanced hydrogen generation activity under visible light irradiation.