Preparation And Mechanism Study Of Non-noble Metal Plasma Photocatalytic Materials

To explore a kind of promising non-noble metal plasmonic photocatalyst represented by Bi, bismuth tungstate that has superior light stability and photocatalysis was selected as a kind of oxide carrier material to investigate the interaction between different sizes of bismuth and bismuth tungstate. The relationship between their plasma resonance effect and photocatalysis was constructed on the basis of the exploration of the correlation among bismuth tungstate interface structure, electron transfer and its photocatalytic activity. Moreover, a kind of non-oxide carrier material-carbon represented by graphene was choosed to investigate the impact of the interaction between graphene and bismuth on their plasmon resonance effect, photocatalytic activity and chemical stability. Finally on the basis of the above researchs, Bi2WO6-Al and Bi2WO6-Sn were prepared to explore the interaction between the carrier material and "poor" metal, which affects the plasmon resonance effect and their photocatalytic performance.Several conclusions could be drawn as written below:(1) There exists strong interactions between bismuth tungstate and graphene, which makes a positive shift of band structure and a wider valence band in the compositie. As a result, the photocatalytic activity of bismuth tungstate-graphene was improved by the interactions of their interfaces and superior conductivity of graphene.(2) The plasma effects of Bi were more obvious as their sizes in the range of 20-200 nm, where their photocatalytic activities were enhanced as well. The plasma resonance absorption were observed in ultraviolet and near infrared region in the bismuth samples with hoist and hollow structure which have the highest photocalystic activity. Meanwhile, the plasmon resonances of Bi were affected by their surface functional groups and structural defects. However, the chemical stability of bismuth was pretty low due to the surface oxidization.(3) With an increase of size and agglomeration of bismuth practices, the chemical stability of Bi was enhanced by the graphene carrier material. The photocatalytic activitiy of bismuth-graphene was increased due to the excellent conductivity of graphene and stronger light absorption in the system of ethylene glycol, however, the photocatalytic activitiy of bismuth-graphene was reduced for the change of surface functional groups and surface defects in thse system of acetic acid.(4) In the samples of Bi2WO6-Bi, small size (less than 5 nm) of bismuth makes little effect on the light absorption of Bi2WO6. The photocatalytic activity of Bi2WO6-Bi was enhanced due to the heterojunction between bismuth and Bi2WO6 and the formation of surface defect in Bi2WO6. The absorption edge of bismuth tungstate red shifted as the size of bismuth is about 20 nm with a plasmon resonance peak at about 240 nm, however the photocatalytic activity of this sample decreased on account of the surface active sites of Bi2WO6 were occupied by bismuth. Moreover, the light absorption performance of Bi2WO6 has little change as coupling bismuth with a size of 200 nm that makes a strong plasmon resonance effect and leads to an increasing photocatalytic activity. A blue shift of absorption edge was observed in Bi2WO6 as coupling larger size (more than 200 nm) of bismuth, in contrast, its photocatalysis was improved for the formation of heterojunction and surface defects. The change of light absorption in carrier material comes from the formation of chemical band between bismuth tungstate and bismuth which changes the electron distribution of their interface and result in different band structure.(5) Compared to pure bismuth tungstate, the absorption edges of Bi2WO6-Al and Bi2WO6-Sn were red shifted. Furthermore, with the decrease of the sputtering time, the red shift effect was more obvious, the photocurrent and photocatalytic activity were enhanced as well.