Improved Photocatalytic Activity Of Two Kinds Of Typical Photocatalysts Incorporated With RGo And Noble Metal

Energy crisis and environmental pollution have seriously hindered the sustainable development of human society.Photocatalysis technology has been widely used and studied in the field of energy and environment because of its green,environment-friendly,and low cost.The core of photocatalysis technology is the design and preparation of high-performance photocatalysts.However,two key problems of photocatalysts are put forward,which are low efficiency of photogenerated carrier separation and optical absorption.To conquer these two problems,especially for the single-component photocatalysts,effective methods such as morphology design,ion doping,and exposed facets of crystal surface have been proposed,but the photocatalytic performance of single-component photocatalysts prapred by these methods is relatively limited.Therefore,the typical inorganic(TiO₂)and organic(g-C₃N₄)semiconductor photocatalysts are taken as base materials,and the reduced graphene oxide(rGO)with high conductivity as well as the noble metals with surface plasmon resonance effect are introduced as the co-catalysts to construct multi-component photocatalysts in this paper.Meanwhile,TiO₂and g-C₃N₄were doped and morphologically designed.Based on the synergistic effect of co-catalyst modification and single component,the carrier separation efficiency was effectively improved and the optical absorption efficiency was increased.The detailed research contents are as follows:Firstly,aiming at the key problem of low efficiency of TiO₂photocarriers separation,boron-doped rGO/rutile TiO₂nanorods composite photocatalysts were prepared via a novel one-step hydrothermal method for the first time.It was found that the graphene oxide was reduced and boron was doped,in the rutile TiO₂nanorods prepared by a hydrothermal method.The photocatalytic degradation ability for NO_Xand MO of 7.5%boron-doped rGO/rutile TiO₂is 1.6 times higher than that of pure rutile TiO₂under UV radiation,and 3.9 times higher than that of pure rutile TiO₂under simulated solar light radiation respectively.These results indicated that the photocatalytic activity of rutile TiO₂is improved effectively due to the synergistic effect of the high specific surface area of rod-shaped morphology,the transfer of photogenerated electrons along the direction of nanorods and high conductivity of boron-doped rGO.Besides,nitrogen-doped rGO/anatase TiO₂composite photocatalyst was prepared by one-step hydrothermal method.It was found that the photocatalytic activity of nitrogen-doped rGO/anatase TiO₂composite for degradation of methylene blue is 2.7 times higher than pure anatase TiO₂under visible light irradiation.Due to the synergistic effect of active reaction crystal surface resulting from anatase phase TiO₂octahedral morphology and high conductivity of rGO,the photocatalytic activity of nitrogen-doped rGO/anatase TiO₂composite was effectively improved.Secondly,g-C₃N₄has a graphite-like stacking structure,which determines its low specific surface area,and repaid recombination of the photo-generated electrons and holes in its layer due to these photo-generated carriers cannot reach the surface to participate in the photocatalytic reaction.Therefore,the g-C₃N₄with high specific surface area was prepared through a simple thermal stripping method.The specific surface area is 189.9m²/g,which is 34 times higher than raw g-C₃N₄.High specific surface area leads to abundant reaction sites and the photogenerated electrons are easy to reach the surface to participate in the photocatalytic reaction,which improves the efficiency of carrier separation.However,the band gap of g-C₃N₄increased due to the quantum confinement effect and the optical absorption efficiency decreased.Besides,Ag nanoparticles were uniformly deposited on g-C₃N₄prepared by a photo-deposition method.The results revealed that the photocatalytic activity of Ag/g-C₃N₄for degradation of methylene blue is 10 times higher than that of ordinary g-C₃N₄under visible light irradiation.Due to the synergistic effect of the high specific surface area of g-C₃N₄and the surface plasmon resonance effect of Ag nanoparticles,the photocatalytic activity of g-C₃N₄was effectively improved.Moreover,P-doped g-C₃N₄was prepared via thermal polycondensation.It was found that P-doping led to the change of the electronic structure of g-C₃N₄,which effectively reduced the band gap and improved the utilization of visible light.Furthermore,Au nanoparticles were deposited on the surface of P-doped g-C₃N₄prepared by a photo-deposition method.Compared with the raw g-C₃N₄,the photocatalytic hydrogen evolution activity of the optimal Au/P-doped g-C₃N₄increased by 8.4 times under visible light due to the improved carrier separation and enhanced light utilization.Thirdly,rGO and Au nanoparticles are anchored on the surface of the ultrathin layer g-C₃N₄through a one-step photo-deposition method.The results indicated that the monodisperse Au nanoparticles were uniformly deposited on one side of the thin layer g-C₃N₄,while rGO was well deposited on the other side.This novel structure promotes the transfer of photo-induced electron in both directions.The performance of photocatalytic hydrogen evolution and degradation of methylene blue of the optimal Au/g-C₃N₄/rGO were 9.6 and 6 times higher than those of raw g-C₃N₄under visible light,respectively.The enhancement of photocatalytic activity results from the novel structure,surface plasmon resonance effect of Au nanoparticles,high conductivity of rGO,and ultrathin layer structure with high specific surface area.Overall,the enhancement of photocatalytic activity can be attributed to the synergistic effect of co-catalyst and rational morphology design.