Synthesis Of N/TiO₂ Nanofilm Electrode And Its Photoelectrocatalytic Performance

Titanium dioxide(TiO2),as a kind of photocatalysts,which has high photocatalytic activity,low cost,easy to industrialization produce,stable performance and non-toxicity,has been widely attracted researchers' attention.Recently,researches have focused on the pollutants removal,air purification and utilization of solar energy.However,TiO2 as a kind of wide bandgap semiconductor(3.2 eV for anatase and 3.0 eV for rutile),only can absorb the UV light?(387 nm),occupying about 5-7%of sunlight,which restrict its large-scale application and promotion of industrialization.So,researches focused on extending the optical absorption and improving utilization efficiency of solar energy,have always been a hot topic in recent decades.In this study,the solar-driven N/TiO2 film electrode was synthesized in a mixture electrolyte of nitric acid,ethylene glycol and water solution by in-situ anodic oxidation technology on the titanium substrate.The morphology structure,crystal structure and optical absorption characteristics of TiO2 film electrode were investigated by SEM,XRD,UV-vis-NIR,XPS,ESR and other analysis methods.Moreover,the photoelectrocatalytic activity was evaluated by the degradation of methyl orange(MO).On this basis,we study the factors that influence the photocatalytic activity and the mechanism of the degradation of MO,This research has obtained the following results:(1)The controllable preparation of N/Ti02 films was obtained by optimizing the preparation conditions,such as anodic oxidation voltage,oxidation time,electrolyte composition,the annealing condition.The optimal preparation condition was obtained:electrolyte composed of 1 wt%HNO3,1 wt%of H2O and ethylene glycol(EG)solution,the anodic oxidation voltage of 40 V,oxidation time for 10 min,and calcined at 500?for 1 h.(2)SEM images indicated that a three-dimensional pine branched-like structure was obtained,which consisted of some nano-branches distributed on the same central axis.XRD results showed that the crystal structure of N/TiO2 is a kind of mixed crystal structure of anatase(A)and rutile(R),and the optimal crystal ratio is 0.8:1 for A:R.The XPS results showed that the N atoms exist in N/TiO2 films with the form of interstitial atom(Ti-O-N).UV-vis-NIR results showed that the N/Ti02 film electrode had the wide absorption spectra from ultra-violet to near-infrared light(200-2500 nm),and the bandgap calculation displayed that two exotic level existed in the forbidden band of TiO2,namely the impurity level of N2p and defect level caused by oxygen vacancy,which lead to the forbidden band width of N/TiO2 reduced to 0.72 eV.Electrochemical workstation test results showed that the N/TiO2 film electrode produce higher photocurrent density of 0.2 mA/cm2 and better photoelectrochemical property than pure TiO2 film under sunlight.(3)The photoelectrocatalytic activity of N/TiO2 film electrode was evaluated by photoelectrocatalytic degradation of MO in UV and sunlight.The results indicated that the sample showed excellent photoelectrocatalytic activity,the MO degradation rate can reach up to 90%only 10 min under UV light,and 90%within 2 h under sunlight.The main factors in the preparation process and photoelectricatalytic process,such as bias,the initial pH of solution,light intensity and so on,have a great influence on the degradation efficiency of MO.What's more,N/TiO2 film electrode exhibited a good stability and efficiency.It remains high photoelectrocatalytic activity after repeated 10 times and the photoelectrocatalytic activity of the electrode has no decay.