Novel C3N4–CdS composite photocatalysts with organic–inorganic heterojunctions: in situ synthesis, exceptional activity, high stability and photocatalytic mechanism

The g-C(3)N(4) photocatalyst was synthesized by directly heating the low-cost melamine. The methyl orange dye (MO) was selected as a photodegrading goal to evaluate the photocatalytic activity of as-prepared g-C(3)N(4). The comparison experiments indicate that the photocatalytic activity of g-C(3)N(4) can be largely improved by the Ag loading. The strong acid radical ion (SO(4)(2-) or NO(3)(-)) can promote the degrading rate of MO for g-C(3)N(4) photocatalysis system. The MO degradation over the g-C(3)N(4) is mainly attributed to the photoreduction process induced by the photogenerated electrons. Our results clearly indicate that the metal-free g-C(3)N(4) has good performance in photodegradation of organic pollutant.

As a new kind of polymeric semiconductors, graphitic carbon nitride (g-C(3)N(4)) and its incompletely condensed precursors are stable up to 550 degrees C in air and have shown promising photovoltaic applications. However, for practical applications, their efficiency, limited e.g. by band gap absorption, needs further improvement. Here we report a "structural doping" strategy, in which phosphorus heteroatoms were doped into g-C(3)N(4) via carbon sites by polycondensation of the mixture of the carbon nitride precursors and phosphorus source (specifically from 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid). Most of the structural features of g-C(3)N(4) were well retained after doping, but electronic features had been seriously altered, which provided not only a much better electrical (dark) conductivity up to 4 orders of magnitude but also an improvement in photocurrent generation by a factor of up to 5. In addition to being active layers in solar cells, such phosphorus-containing scaffolds and materials are also interesting for polymeric batteries as well as for catalysis and as catalytic supports.