Promoted photocatalytic hydrogen evolution via double-electron migration in Ag@g-C₃N₄ heterojunction

The unsaturated edge Ag introduced on the surface of photocatalysts plays an important role in boosting photo-excited electrons for the photoreduction H₂O reaction. However, a moderate and tractable strategy to efficiently expose edge Ag remains an enormous challenge. For this purpose, a core skeleton with ‘Ag conductive nanosphere array’ inside and a two-dimensional sheet structure with g-C₃N₄ layer outside are formed. The introduction of Ag nanospheres into g-C₃N₄ not only enlarges the distance between g-C₃N₄ nanolayers, but also increases the exposure of Ag nanospheres. When Ag intimately contacts with g-C₃N₄, the electrons of g-C₃N₄ voluntarily flow to the Ag. Consequently, a built-in electric field (IEF) has been formed at interface of Ag@g-C₃N₄ heterojunction, which prevents the continuous flow of electrons from g-C₃N₄ to Ag. Under irradiation, the e⁻ accumulated in Ag tend to recombine with the h⁺ in the valence band of g-C₃N₄ which is driven by Coulomb interaction and IEF. Ag nanospheres are fabricated as a co-catalyst to decorate the g-C₃N₄ nanolayer, which hinder the conglomeration of g-C₃N₄ nanolayers. Moreover, Ag@g-C₃N₄ heterojunction provides polyunsaturated edge Ag as active sites, inducing prolonged lifetime of photogenerated electrons and formed the unique charge transfer channels. In addition, abundant nitrogen vacancies are formed, which strengthens the chemisorption of H₂O. As a result, supreme Ag@g-C₃N₄ realizes a high H₂ evolution of 312.5 μmol and preserves a good sustainability. This paper emphasizes the importance of unique electron transfer pathway and chemisorption of water for photoreduction H₂O.