Preparation And Activity Research Of Bismuth Phosphate Matrix Compound Materials

In recent years, the ecological environment pollution becames more and more seriously, the traditional processed methods which had many disadvantages can't meet the requirements. Due to its advantages in pollution governance, the semiconductor photocatalyst has caused increasely attention. As a kind of oxyacid salt catalysts, BiPO4 exhibites great photocatalytic performance, but its light response range locates in ultraviolet region and the separation efficiency of electronics and holes are poor. In order to improve its catalytic property and extend its light response range, we designed lots of methods such as non-metallic element doped, precious metals modified and other semiconductor compound to enhance its performance. The BiPO4 nanorods synthesized by a simple one step hydrothermal method were used as base material. The crystal structure, micro morpholog, light absorption performance of samples were characterized by some measurgin methods, the photoelectric conversion performance, the separation efficiency of electron-hole pairs and the migration rate of photo-generated carriers were measured by electrochemical workstation, the catalytic performance of samples were measured through degradation of pollutant MO by photocatalytic apparatus.(1) N-doped BiPO4 photocatalyst was produced through one step hydrothermal method with NaN3 as N source. The valence and conduction bands, density of states and the band gap energy of BiPO4 are calculated with first-principles. The results showed that both BiPO4 and N-doped BiPO4 have same monoclinic structure. The substitution of O2- by N3- ions in BiPO4 could not only cause the red-shift of the adsorption edge, but also change the morphology. The photocatalytic activity of BiPO4 was enhanced about 50% under UV light irradiation when the molar ratio of N/Bi is 0.2, this can be ascribed to the N3- introduced into BiPO4 crystal lattice restrain the recombination of photogenerated electron-hole pairs. However, overdoping would decrease the photocatalytic activity of BiPO4.(2) The Ag3PO4/N-doped BiPO4 (N-BiPO4) core-shell structure photocatalyst was synthesized by a simple in-situ growth strategy in C2H5OH organic solvent. The separation of photogenerated electron-hole was enhanced by the doping of nitrogen, because of the emergence of N-O impurity energy levels. The enhanced photocatalytic activity of Ag3PO4/N-BiPO4 could be ascribed to the in-situ formation of chemical bonds between Ag3PO4 and N-BiPO4, which accelerate the separation of electron-hole pairs. The photocatalytic performance of the as-synthesized Ag3PO4/N-BiPO4 was evaluated by monitoring the decolorization of methyl orange under sunlight irradiation. Ag3PO4/N-BiPO4 was capable of bleaching 95% MO within 40min.(3) The g-C3N4/Au/BiPO4 as a hierarchical Z-scheme system was prepared through three steps at different reaction temperatures, using thiourea as precursor to synthesize g-C3N4. Their photoelectric activities were also investigated via the degradation of methyl orange (MO). The g-C3N4/Au/BiPO4 exhibited remarkably promoted photocatalytic activities and photoelectrochemical properties compared with g-C3N4, BiPO4 and g-C3N4/BiPO4. The electrochemical impedance spectra and photocurrent results also proved that efficient charge separation and better electron transport properties were achieved by g-C3N4/Au/BiPO4. So excellent performance could be attribute to the Z-scheme system, which improved the separation efficiency of photo-induced carriers and suppressed recombination of electron-holes. It was worth pointing out that the metallic Au species not only acted as the solid state electron mediator, but also could absorbed photons from incident light and present surface plasmon resonance effect in this hybridization system.(4) The Bi(NO3)3·5H2O was used as raw material, adopted the hydrothermal method to produce Bi2O3/BiPO4 heterojunction, then coated it with g-C3N4, formed g-C3N4/Bi2O3/BiPO4 material system. The optical, morphological and photoelectrochemical (PEC) properties of BiPO4, g-C3N4/BiPO4, Bi2O3/BiPO4 and g-C3N4/Bi2O3/BiPO4 hierarchical Z-scheme system were studied. More than 90% photodegradation of methyl orange (MO) with the exposure of simulated solar light was achieved within 160min with the g-C3N4/Bi2O3/BiPO4, which displayed remarkably promoted photocatalytic activities than other samples. The electrochemical impedance spectra and photocurrent results also proved that efficient charge separation and better electron transport properties were achieved by g-C3N4/Bi2O3/BiPO4. In general, the addition of g-C3N4 can guide the residual electrons on p-type Bi2O3 to recombine with photoholes of g-C3N4 and make sure the left carries exhibit stronger oxidation and reduction ability to boost the production of active groups.