Efficient Photocatalytic H2 Evolution by Hexaniobate Nanosheets Grafted with Copper Nanoclusters

摘要

Hexaniobate nanosheets (K_(4-x)H_xNb6O_(17)) were combined with Cu~(2+) ions by grafting, a green one-step methodology. The resulted nanocomposite exhibits high surface area with most of the Cu~(2+) ions strongly connected to the hexaniobate layers as amorphous nanoclusters. Photocatalytic experiments evidence that the Cu-grafted hexaniobate can act as an efficient photocatalyst for H2 evolution. The best performance for the Cugrafted hexaniobate was reached when the Cu concentration was 0.5 wt% (1.62±0.10 mmog~(-1)h~(-1)), whereas hexaniobate layers with 0.5 wt% photodeposited Pt exhibited a hydrogen evolution rate of 0.95±0.04 mmolh~(-1)g~(-1) under the same experimental conditions. Grafting leads to covalently bounded Cu species onto the hexaniobate surface, ensuring a strong electronic interaction. Detailed XPS and EPR studies evidence that the initial Cu~(2+) species are promptly reduced to Cu~(1+)/Cu~0 under illumination. The prominent performance of Cu-grafted samples was related to the improved charge-separation efficiency as shown by ns-transient spectroscopy. Therefore, the present methodology offers a green option to produce efficient Earth-abundant-based photocatalysts for H2 evolution.