| To design and synthesize catalysts with enhanced photoactivity forwater splitting in the visible light is essential to realize the solarhydrogen.In this study, we investigated thoroughly the preparation condition ofrare earth metal ions and some non-metal ions doping WO3 and theeffects of dopants on its photocatalytic activity. Some significant resultswere obtained. New and interesting results are as the following:We investigated systematically the effect of rare earth metal ionsdoping WO3 on its activity of photocatalytic oxygen production by visiblelight irradiating. The high active photocatalysts of rare earth metal ironsdoping WO3 were prepared by the solid-state sintering methord. Amongall the doped samples, WO3 doped with Pr3+ has the highest activity.When the doped mass of Pr3+ was 0.05%(wt.), the calcinated temperaturewas 600℃and the calcined time was 4 h,the photocatalytic activity ofpr3+-doped WO3 had increased by 112% compared to pure WO3 aftervisible light irradiating for 12 h. The analysis of structure of Re-WO3using XRD,SEM,XPS,DRS and PL spectra indicated that rare earthmeatl ions doping in WO3 didn't influence the crystal patterns, but thedopant produced lattice deformation which caused the change of theelectron density in WO3. The doped WO3 photocatalytic activities were inthe order: Pr-WO3＞La-WO3＞Nd-WO3＞Y-WO3＞Sm-WO3＞Ce-WO3＞Dy-WO3=Yb-WO3＞Er-WO3＞Tb-WO3＞Gd-WO3＞pure WO3。When the doped mass content of Y3+ was 0.05%(wt.), the oxygenproduction rate was 200μmol·L-1·h-1 after UV-light irradiation, whichwas 24% higher than that of undoped WO3; the oxygen production ratewas 161.3μmol·L-1·h-1 after visible light irradiation, which was 73.4%higher than that of undoped WO3; and realized disbreaking itsphotocatalytic activities after UV-light irradiation when enhancing itsphotocatalytic activities after visible light irradiation. The photocatalyst of non-metal N, C, S, F doped WO3 had beenprepared by the solid-state sintering methord. The photocatalyticreactivity of WO3 for oxygen production was studied while Fe3+ was usedas electron donor. The results showed that when the doped mass contentof non-metal N, C, S, F was 2.0%(wt.), the calcinated temperature was500℃and the calcined time was 2 h, the photocatalytic reactivity ofdoped WO3 were separately 118μmol·L-1·h-1,171μmol·L-1·h-1,200μmol·L-1·h-1,207μmol·L-1·h-1, which had increased by -16%,22.2%,43%,47.6% than pure WO3 after UV-light irradiating for 12 h; thephotocatalytic reactivity of doped WO3 were separately 83μmol·L-1·h-1,115μmol·L-1·h-1,148μmol·L-1·h-1,89μmol·L-1·h-1, which had increasedby-14.9%, 24%, 59%, -8.2% than pure WO3 after visible light irradiatingfor 12 h. C and S dopants enhanced the photocatalytic property of WO3both in visible light and UV-light range.The band structure and density of states of WO3 photocatalysts dopedwith non-metals have been analyzed by the first principles calculationswith the density functional theory. The calculation results revealed thephotocatalytic activity differences from the change of electronic structureand showed that the fermi energy level of WO3 moved to the conductionbands when doping with C,S and F and new levels occurred between theconduction and valence bands. The energy gap of WO3 was reduced andphotoproduced electrons and holes were easily excited with lower energycompare with the undoped WO3. There is a good agreement between thecalculation and experimental results. The fermi energy level of WO3moved to the valence bands when doping with N and new levels occurredbetween the conduction and valence bands. The energy gap of WO3 wasreduced, but experimental results showed that doping of 2.0% Ndecreased the photocatalytic activity of WO3 photocatalysts. Thisphenomena was caused possibly by new combined center beingsupported at the same time of decreasing energy gap. |
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