PHOTOCATALYTIC REDUCTION OF CO2 OVER A HYBRID PHOTOCATALYST COMPOSED OFWO3 AND GRAPHITIC CARBON NITRIDE (g-C3N4) UNDER VISIBLE LIGHT

摘要

Carbon dioxide (CO2) is one of the major compounds responsible for global warming, which has now become a global environmental issue because fossil fuel consumption will cause a monotonical increase in the atmospheric CO2 concentration in the future. Therefore, CO2 conversion or energy-oriented use is a priority subject of investigation throughout the world. Effective utilization of clean and abundant solar energy for CO2 conversion will be a promising solution not only for energy issues due to the consumption of natural energy sources but also for many problems caused by greenhouse gases. In order to efficiently utilize solar energy, photocatalytic CO2 reduction to produce useful fuels under visible light, mimicking artificial photosynthesis, is one possible solution. Actually, photocatalytic reaction over semiconductor photocatalysts has the potential to reduce CO2 into hydrocarbons using water as an electron donor. For instance, Inoue and coworkers first reported photocatalytic CO2 reduction in a semiconductor aqueous suspension to produce hydrocarbon fuels such as formaldehyde (HCHO), formic acid (HCOOH), methanol (CH3OH), and methane (CH4). In addition, metal oxide semiconductor photocatalysts including titanium(iV) oxide (TiO2) can produce formic acid (HCOOH), formaldehyde (HCHO), methanol (CH3OH), and methane (CH4) . However, quantum yields for photocatalytic CO2 reduction have been low. The carbon source of the products is not clear. However, most of the photocatalytic CO2 reductions using metal oxide semiconductor photocatalysts are carried out under UV-light irradiation, and the synthetic process and recipe of the photocatalysts are complicated. Therefore, visible-light-driven materials with high efficiency and stability represent a central challenge in the field of photocatalytic CO2 conversion for energy-oriented use.