Synchronous Synthesis Of Cu₂O/Cu@Carbon Nanomaterials Photocatalysts Using Hydrogel As Template And Characterization Of Their Performances

Photocatalysis have developed as an important technique in addressing environmental problems and have received extensive attention recently.Cu2O.a semiconductor photocatalysis with a narrow band gap energy(2.0 eV),can effectively utilize visible light,which accounts for 46%solar spectral energy.It has drawn increasing attention in environmental energy field,such as eliminating persistent contaminants,photocatalysis hydrogen production and photocatalysis CO2 reduction.Aming at solving the disadvantages of poor photochemical stability,low photocatalytic acitivity of Cu2O and complex operation,high cost during synthesis,this paper synchronously synthesized a seires of Cu2O/Cu@carbon nanomaterials(Cu2O/Cu@CN)composite phootcatalysts using sosium alginate hydrogel as template based on great references.Cu2O/Cu@CN have been applied in photocatalytic degradation of organic pollutants in the environment.The structure-activity relationship of Cu2O/Cu@CN and the mechanism of photocatalytic degradation of organic pollutants have been investigated.The main contents and results are as follows:1.Under no reductive agent and dispersant participation,Cu2O/Cu@CN composite photocatalysts were synchronously synthesized using sodium alginate hydrogel as template through immobilization of Cu2+ at unique crosslinking sites,in-situ precipitation and calcination under nitrogen protection.The effect of different synthesis conditions(sodium algiante fraction,crosslinker concentration,and precipitant concentration)on component,morphology of composite photocatalysts and their performance were studied by photocatalytic degradation of methyl red(MR)under visible light irradiation.On the one hand,results showed that the unique "egg-box"structure of sodium algiante hydrogel could achieve well immobilization of Cu2+ and the formed 3-D hydrogel network could achieved fully dispersion of Cu2O nanoparticles.On the other hand,sodium alginate hydrogel could be in-situ catalyzed by Cu nanoparticles and be carboniazed as carbon nanomaterials with different morphologies.Results showed that higher sodium algiante fraction,larger specific surface area of the composite photocatalysts.Besides,crosslinker concentration and precipitant concentration have great influence on the morphology of Cu2O.The embedded Cu2O-carbon nanocapsules strucuture could be obtained by adjusting crosslinker concentration and precipitant concentration controllably.The sample with embedded structure exhibitted excellent activity.The maximum removal efficiency of methyl red(MR)was 90%under the systhesis conditions optimized with sodium alginate fraction of 5wt%,crosslinker cocnentration of 0.25 mol/L and precipitant concentrarion of 0.5 mol/L.Results of catalytic mechanism shovwed that the main active apecies in photocatalytic system includes ·O2-species and OH species.2.The recyclable magnetic Cu2O/Cu@CN composite photocatalysts were synchronously synthesized using sodium alginate hydrogel as template through crosslinking in Fe2+/Cu2+ mixed solutioin,in-situ precipitation and calcination in nitrogen protection.The effect of different synthesis conditions(ratio of Fe2+/Cu2+,crosslinker total concentration,and precipitant concentration)on component,morphology of composite photocatalysts and their performance were studied by photocatalytic degradating of methyl blue(MB)under visible light irradiation.Results showed that Fe3O4 nanoaparticles could facilitate to improve the photocatalytic activity of Cu2O/Cu@carbon nanomaterials composites.The maximum removal efficiency of methyl blue could reach 95%under the systhesis conditions optimized with Fe2+/Cu2+ratio of 2:1,crosslinker total cocnentration of 0.2 mol/L and precipitant concentrarion of 1.5 mol/L.Based on the results of VSM,the magnetic composite photocatalysts can be easily recycled by applying an external magnetic field.And the photocatalytic activity towards degradation of MB could maintain above 90.5%after 4 times recycling.Meanwhile,active species composition in photocatalytic system was investigated,including ·O2-·OH and h+.3.To further improve the photocatalytic activity of Cu2O/Cu@CN composite photocatalysts,the reduced graphene oxide(rGO)doped Cu2O/Cu/carbon nanomaterials composite photocatalysts were synthesized by incorporating graphene oxide(GO)in sodium algiante hydrogel.Results showed that the obtained rGO-doped samples exhibited higher photocatalytic activity towards degradation of p-chloronitrobenzene(p-NCB)compared to sample without rGO under visible light irradiation.The enhanced photocatalytic activity was benefit from good conductivity of rGO and increasing rGO contents could enhance photocatalytic activity.Based on the results of EPR and radical quenching experiments,active species composition in photocatalytic system was incestigated.Results showed that ·O2 species were the main species,and ·OH and h+ speies were the secondary species.