Study On The Green And Controllable Preparation Of Nano Tio₂ With High Photocatalytic Activity Based On Deep Eutectic Ionic Liquids

Hydrogen is an attractive alternative to fossil fuels that addresses several environmental and energy shortage issues.Among the different nanomaterials,TiO₂ is the most studied and commonly used semiconductor photocatalyst for hydrogen production,conversion of CO₂ to energy-rich hydrocarbon fuels and pollutant degradation due to its excellent stability,photocorrosion resistance,nontoxicity,low cost,high catalytic activity and environment friendly.However,there are many problems on the conventional method of preparing TiO₂,such as complicated synthesis steps,longer reaction time,higher calcination temperature,and addition of an acid as inhibitors,a surfactant as template agents,an organic as solvent diluents,etc,which results in poor reproducibility,high energy consumption,environmental pollution in batch preparation of TiO₂.These problems have seriously affected the industrialization process of nanomaterial preparation and application.Therefore,the mild,green,rapid and efficient regulation of TiO₂ still faces enormous challenges,and it is urgent to find a green solvent to replace the traditional solvent to avoid environmental pollution in the chemical production process.Deep eutectic ionic liquids（DEILs）are promising solvents in the green and mild preparation of high active nanomaterial due to their low cost,biodegradable,nontoxic,easy large-scale preparation and similar physicochemical properties with conventional ionic liquids.DEILs usually contain a hydrogen bond donor like a urea,amide,acid,or polyol,and a hydrogen bond acceptor like choline chloride（ChCl）.Particularly,DEILs are typical designer solvents to create well-defined nanomaterials including shapecontrolled nanoparticles and colloidal assemblies.Usually,DEILs can fulfill multiple roles in the synthesis of nanomaterials:acting as supramolecular template,solvent and stabilizer.The ability to tailor the physicochemical properties of DEILs by changing the type and proportion of hydrogen bond donors and acceptors proves that DEILs have a wide range of applications in the synthesis of nanomaterials.Therefore,in first section,ChCl/oxalic acid DEIL was prepared and was used for the fast synthesis of new crassula peforata-like TiO₂ with（001）and（101）planes under mild reaction conditions as the solvent,template and inhibitor.Then the synthesis mechanism of crassula peforata-like Ti O₂ was studied by time evolution test and exploring the influences of different hydrogen-bond donors and hydrogen-bond acceptors on TiO₂ shapes.Finally,the photocatalytic hydrogen production activity and stability of TiO₂ was investigated.The fluorescent and electrochemical impedance measurement was further demonstrated the reason of high yield hydrogen activity.The photoelectric current test and IPCE test further verified that TiO₂ synthesized by ChCl/oxalic acid DEIL had good photoelectric performance.These findings will provide a new method for the green,fast and easy-controllable preparation of new and high efficiency catalysts,and a new way for the batch and large-scale preparation of nanocatalysts based on the excellent physical and chemical properties of DEILs.In the second section,the topic is still focused on the synthesis of TiO₂ based on DEILs,still maintain the advantages of green,mild,controllable,one-step synthesis method,and the breakthrough point is to construct the heterojunction TiO₂ with the change of DEILs,achiving the transformation of TiO₂ from monocrystalline to heterojunction brookite/rutile TiO₂,for further improving the activity of TiO₂.Therefore,the functional ChCl/betaine/oxalic acid DEIL was synthesized and used in the preparation of brookite/rutile TiO₂ in one-step and rapid method under mild and green conditions.The results show that the proportions of brookite TiO₂ and rutile TiO₂ in the as-synthesized heterojunction TiO₂ synthesized under different ratios of ChCl and betaine are different,and then the morphology and photocatalytic hydrogen production of heterojunction TiO₂ are also studied.Based on the excellent physico-chemical properties of DEILs,these studies will provide a green,fast and easily controlled method for preparing highly efficient heterojunction catalysts and also provide a method for large-scale batch production of heterojunction photocatalysts.There were currently very few research of DEILs applied in the synthesis of nanomaterials,but according to the results of this paper,the synthesis methods of nanomaterials based on DEILs will open the door to the synthesis of semiconductor photocatalyst,and open a new era of fast green and controllable preparation of nanomaterials with high photocatalytic activity based on deep eutectic ionic liquids.