Fabrication Of Visible Light Response Bi-based Photocatalysts And Their Photocatalytic Enhancement Mechanism

Due to their good photoresponsive performance,strong oxidizing ability,low toxicity and low cost,bi-based semiconductors are favored by researches in the photocatalytic oxidation.However,there are still many shortcomings,such as photo-corrosion phenomenon,the rapid recombination of photogenerated electron-hole pair,the low migration rate of photogenerated carrier and limitable sorts of of pollutants that can be degraded,which limit their practical applications.Genenrally,in order to further enhance the photocatalytic performance,many efforts have been developed,such as formation of heterojunction,metal loading,doping and the combination with other techniques.In this paper,three methods were employed to improve the photocatalytic performance of Bi-based photocatalyst,including formation a ternary heterjunction,Bi metal loading and the combination with sulfite.The effect of influenced factors,such as photocatalyst dosage,temperature,initial concentration and co-exist ions,on the photocatalytic performance of as-prepared catalysts were systematically investigated,which not only shed light on the enhance mechanism of Bi-based photocatalyst,but also paved the way for the later practical applications.The specific research contents were as follows:1.Bi-BiOBr/BiPO₄ photocatalyst was synthesized by two-step solvothermal method in which ethylene glycol was used as a reducer.It was found that Bi-BiOBr/BiPO₄ has a significant improvement in photocatalytic performance for RhB degradation compared to naked BiOBr and BiPO₄.The photocatalytic degradation rate constant of 0.2-Bi/BiOBr/BiPO₄ was 1.44 h^-1,which was 3.8 times and 14.2 times more than that of pure BiOBr and BiPO₄,respectively.This was attributed to the formation of a ternary heterojunction,which benefiteds the separation of photogenerated electron-hole pairs.Furthermore,with the introduction of metal Bi,the SPR effect of metal Bi can effectively improve the absorption ability of Bi-BiOBr/BiO₄ photocatalyst.The effect of the content and particle size of the metal Bi nanoparticles on the photocatalytic performance was also studied.2.By controlling the preparation temperature,metal Bi was deposited in situ onto the Bi₂WO₆uesd ethylene glycol as reducer with the simultaneous generation of oxygen vacancies.It was found that Bi/BWO-180 had a broad-spectrum property in photocatalytic degradation of organic pollutants due to the synergistic action of metal Bi and oxygen vacancies,especially for high concentration antibiotic wastewater.The effects of impact factors,such as catalyst dosage,pollutant concentration and coexisting inorganic anions on Bi/BWO-180 photocatalytic degradation of CIP solution had also been systematically investigated and a possible photocatalytic degradation mechanism was proposed3.Sulfite had been introduced into Bi₂WO₆ photocatalyst to form Bi₂WO₆/sulfite system.There was a synergistic effect between sulfite and Bi₂WO₆,which effectively enhance its photocatalytic activity.The photocatalytic performance was investigated by choosing methyl orange as model pollutant.It had been found that the reason why the enhanced of photocatalytic activity was that sulfite can react with the photogenerated holes and hydroxyl radicals of Bi₂WO₆,which not only can generate new active sulfite free radicals(SO₃^·-),but also can promote the separation of the photogenerated electron-hole pairs.The effects of the catalyst dosage,the concentration of MO and the inorganic coexisting anions on the photocatalytic properties of the catalyst system were also investigated.