Synthesis Of Carbon Black/Carbon Nitride Intercalation Compound Composite For Efficient Hydrogen Production

Nowadays, we are faced with serious environmental problems and energy crisis. Therefore, it is important to develop novel clean and renewable energies. Photocatalysts are able to utilize solar energy to generate electron-hole pairs, which react with H2O to produce hydrogen. The combustion product of hydrogen is pure water, totally pollution-free. As a whole, photocatalytic water splitting for hydrogen production is an ideal technology to generate clean and renewable energy. And the goal in the field of photocatalytic H2 production is to develop high-activity photocatalysts for efficient solar energy conversion.Graphitic carbon nitride (g-C3N4) polymer, with graphite-like sp2 bonded C-N structure, is a promising catalytic material in the area of photocatalytic hydrogen production, due to their peculiar thermal stability, appropriate electronic structure, and low-cost preparation. As reported, g-C3N4 was successfully synthesized by various methods such as vapor deposition, solventtherma! method and thermal polymerization. However, the g-C3N4 exhibits low quantum efficiency for solar hydrogen production because of the high recombination rate of photogenerated electron-hole pairs.Inserting an intercalation into the interlayer is one of the effective ways for improving the electrical conductivity of layered materials. Herein we have prepared carbon nitride intercalation compound (CNIC) through molten salt method. The as-prepared sample showed better electrical conductivity than g-C3N4 from pyrolysis. And the photocatalytic hydrogen production rate over CNIC is about 10.3 times higher than that over g-C3N4 sample.Another effective method to improve the separation of photogenerated hole-electron pairs is to make a composite between photocatalysts and high-conductivity materials. To further promote the efficiency of separation and transport of photogenerated carriers, high electrical-conductivity materials are coupled with g-C3N4 to make a composite. In the reported studies, carbon materials such as graphene, carbon nanotubes are coupled with g-C3N4 to raise the separation efficiency of photogenerated carriers. However, the size of the materials used as modifier is similar with that of g-C3N4 to be hundreds of nanometers, resulting in limited contact area and nonuniform distribution. The disadvantages limited the efficiency of carrier separation and transport. In our research, conductive carbon black with particle sizes about 20-30 nm is chosed as the coupling material. By TEM observation, we found that the carbon black nanoparticles dispersed uniformly on the surface of CNIC nanotubes. The composite sample showed higher bulk electrical conductivity than CNIC with addition of conductive carbon black. During the photocatalytic reaction, the carbon black nanoparticles on the surface of CNIC nanotubes function as separation centers to efficiently improve the separation and transport of photonegenrated carriers. The as-prepared carbon black/CNIC composite photocatalyst exhibited excellent hydrogen production activity, which is 3.2 times higher than CNIC.