Photocatalytic Degradation And Electrochemical Energy Storage Properties Of CuO/SnO₂ And FeSe₂/TiO₂ Nanocomposites

The energy crisis and environmental pollution is two major problems the world facing today.The pollution due to synthetic dyes is more concern because dye removal from water is difficult as compared to other contaminants treatment,and various conventional technique like adsorption,precipitation and coagulations are used so far for water treatments.Recently,heterogeneous photocatalysis got much attentions due to its high efficiency,low cost,and wide applications.Simple photooxidation and reduction is occurring when photocatalyst exposed to light the electrons from its valence band VB to conduction band CB,these electrons then come to the surface of the material,react with O₂and H₂O to generate radicals which then combines with dye and do the dye degradations.On the other hand,over population and depletion of energy sources caused energy crisis.Renewable energy source has a significant advantage for their use then non-renewable sources.Energy storage systems have contributed to resolving the energy issue by storing generated energy for later use,batteries,capacitors,and supercapacitors are at the forefront of these storage technologies.There is a lot of research have been reported so far for photocatalytic dye degradation and electrochemical energy storage properties,including various transition metal oxides,selenides like Ti O₂,Sn O₂,Zn O₂,Cd S,Fe Se₂,g-C₃N₄,Bi VO₄and LDH,in which Ti O₂,Cu O,Sn O₂and Fe Se₂showed excellent activity in both,in single and in combined form.Sn O₂and Cu O is considered a good alternative to Ti O₂due to its abundant availability,high surface area and excellent option for heterojunction with other semiconductor material.Our first study includes,the synthesis of Cu O/Sn O₂nanocomposite for dye degradation and for electrochemical energy storage application.The three distinct Cu O/Sn O₂nanocomposites with varied ratios of Cu O with Sn O₂were prepared.The degradation activity of the Cu O/Sn O₂nanocomposite were checked against methylene blue and show high activity.The lower loading of Cu O over Sn O₂（AT-1）displayed higher photocatalytic degradation compared to pure Sn O₂and Cu O.CV analysis reveals a pseudocapacitive charge storage mechanism from 0.0to 0.7 V in a potential window in an aqueous medium.The capacitive performance was also investigated for all electrodes,and we observed that a high capacitance of 260/155 F/g at 1/10 A/g was attained for the AT-1 electrode compared to others,specifying good rate performance.In the second study,Fe Se₂/Ti O₂nanocomposites were prepared via solvothermal in/ex-situ sol-gel method with different wt.%composites for efficient Rh B degradation and supercapacitor applications.The result shows that the composite of Fe Se₂and Ti O₂increases the absorption,which collectively enhances the separation of the charge carriers and redox activities.The photocatalytic activities analysis demonstrated that the FT-1 sample reveals the fastest removal of the Rh B dye in just 60 min(FT-2,Fe Se_2,and Ti O₂=90,100,and 180 min)with good stability（98%）after several cycles.As supercapacitor electrode materials,all electrodes showed well-defined peaks in their CV loops and voltage plateaus in their charge/discharge profile,illustrating the pseudocapacitive charge storage mechanism.The higher capacitance of 295（FT-1）,than other electrodes（Fe Se₂,Ti O₂,and FT-2=210,115,and 240 F/g）at 1A/g was obtained to reach 180 at 10 A/g,resulting in an enhanced rate capability of 82%.The high-rate capability is the cause of its more minor charge transfer resistance,resulting in higher conductivity and promoting rapid charge transport kinetics.