Study on the separation mechanisms of photogenerated electrons and holes for composite photocatalysts g-C3N4-WO3

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.

The production of H(2) by photocatalytic water splitting has attracted a lot attention as a clean and renewable solar H(2) generation system. Despite tremendous efforts, the present great challenge in materials science is to develop highly active photocatalysts for splitting of water at low cost. Here we report a new composite material consisting of TiO(2) nanocrystals grown in the presence of a layered MoS(2)/graphene hybrid as a high-performance photocatalyst for H(2) evolution. This composite material was prepared by a two-step simple hydrothermal process using sodium molybdate, thiourea, and graphene oxide as precursors of the MoS(2)/graphene hybrid and tetrabutylorthotitanate as the titanium precursor. Even without a noble-metal cocatalyst, the TiO(2)/MoS(2)/graphene composite reaches a high H(2) production rate of 165.3 μmol h(-1) when the content of the MoS(2)/graphene cocatalyst is 0.5 wt % and the content of graphene in this cocatalyst is 5.0 wt %, and the apparent quantum efficiency reaches 9.7% at 365 nm. This unusual photocatalytic activity arises from the positive synergetic effect between the MoS(2) and graphene components in this hybrid cocatalyst, which serve as an electron collector and a source of active adsorption sites, respectively. This study presents an inexpensive photocatalyst for energy conversion to achieve highly efficient H(2) evolution without noble metals. © 2012 American Chemical Society

A bioinspired iron-based catalyst with semiconductor photocatalytic functions in combination with a high surface area holds promise for synthetic chemistry via combining photocatalysis with organosynthesis. Here exemplified for phenol synthesis, Fe-g-C(3)N(4)/SBA-15 is able to oxidize benzene to phenol with H(2)O(2) even without the aid of strong acids or alkaline promoters. By taking advantage of both catalysis and photocatalysis functions of g-C(3)N(4) nanoparticles, the yield of the phenol can be markedly promoted.