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

Abstract

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.