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Metallic nickel nanoparticles well dispersed in graphitized carbon matrix (Ni@C) by pyrolysis of metal-organic frameworks and leaching treatment of hydrochloric acid could greatly enhance the photocatalytic activity of g-C 3 N 4 under visible light irradiation. For 2.0 wt% Ni@C/g-C 3 N 4 , the average hydrogen evolution rate is 2.15 mmol h −1 g −1 , which is around 88 times higher than that of pure g-C 3 N 4 , and even better than that of platinum-loaded g-C 3 N 4 . The remarkably improved photocatalytic activities through loading Ni@C can be attributed to the cooperative work of Ni nanoparticles and graphene layers, which facilitate the separation of photo-generated carriers and suppress the recombination of the electron-hole pairs. In addition, the hollow onion-like structure can restrain the formation of Ni-hydrogen bonds which modulates desorption of hydrogen. Our studies may open up a promising strategy to design economical noble-metal-free co-catalysts for efficient solar energy conversion. [ABSTRACT FROM AUTHOR]

The search of efficient and stable photocatalysts for the evolution of hydrogen from water using solar energy is of great importance for material science today. Limited by the relatively inferior stability of oxynitrides, the availability of these visible-light-response materials in photocatalysis is still far below what is expected. Here we report a novel oxynitride Ce 0.3 Zr 0.7 O 1.88 N 0.12 as an efficient and stable H 2 -evolving photocatalyst under visible light irradiation, which can further enable overall water splitting by coupling with an O 2 -evolving photocatalyst via Z-scheme. Experimental and theoretical results together reveal that the origin of the excellent activity and stability of Ce 0.3 Zr 0.7 O 1.88 N 0.12 photocatalyst can be attributed to the improved separation rate of photoexcited charge carriers by surface and sub-surface oxygen vacancies. The present study provides a strategy to engineer efficient and stable photocatalysts, and the oxynitride mentioned above could act as a promising candidate of H 2 -evolving photocatalyst for designing a prominent Z-scheme photocatalytic system. [ABSTRACT FROM AUTHOR]