Preparation Of 2-Dimensional Ti₃C₂T_X And Their Applications To Photocatalysis And Photoelectrochemistry

Energy and environmental issues are the long-standing concerns for human beings.As a new energy,solar energy is clean,efficient,and renewable.The photoelectrochemical（PEC）and photocatalytic technology can make full use of solar energy.Therefore,the suitable semiconductor materials play an important role in PEC and photocatalysis.Two-dimensional transition metal carbides（MXenes）are a new family of graphene-like materials.Due to their unique layered structure,superior physical and chemical properties,they have been widely used in lithium ion batteries and supercapacitors.However,there are few studies on PEC and photocatalysis.In this work,Ti3C2TX was used as main research subjects to study its PEC and photocatalytic performance.The two classic semiconductor catalysts（α-Fe2O3 and g-C₃N₄）were combined with the thin Ti₃C₂T_X flakes separately to construct composites.The PEC and photocatalysis were studied separately.The specific research contents are as follows:（1）Study on photocatalytic water splitting using multilayer Ti3C2TX and thin Ti₃C₂T_X.Multilayer Ti₃C₂T_X and thin Ti₃C₂T_X were prepared by simple etching and ultrasonic using Ti3AlC2 as raw materials.The experimental results reveal that the activity of thin Ti₃C₂T_X is significantly higher than that of multilayer Ti₃C₂T_X during photocatalytic reaction,and the activity of hydrogen evolution is 8.66μmolg^-1h^-1.（2）The Sn-dopedα-Fe₂O₃ nanorods were embedded with{001}facets exposed TiO₂ flakes by a facile hydrothermal synthesis and post-calcination treatment（denoted as E-Sn-Fe₂O₃/TiO₂）.The{001}facets exposed TiO₂ flakes were derived from the delaminated Ti₃C₂T_X MXenes（D-Ti₃C₂T_X）without adding extra HF or F ions during hydrothermal synthesis because the surface of D-Ti3C2TX was natively terminated by-F functional groups.The Sn-doped hematite/surface-covered TiO₂（denoted as S-Sn-Fe₂O₃/TiO₂）and Sn-doped hematite（denoted as Sn-Fe₂O₃）were also fabricated for comparison.The optimized results show that the PEC properties of E-Sn-Fe₂O₃/TiO₂ and S-Sn-Fe₂O₃/TiO₂ photoelectrodes are significantly higher than Sn-Fe₂O₃ photoelectrode.The higher PEC performance of the E-Sn-Fe₂O₃/TiO₂ and S-Sn-Fe₂O₃/TiO₂ compared with the Sn-Fe₂O₃ may be ascribed to the heterojunction of Sn-Fe₂O₃/TiO₂ and the Ti⁴⁺incorporation upon 700oC calcination.The unique architecture of embedded TiO₂ can improve the interfacial contact between theα-Fe₂O₃ and TiO₂ as well as the light harvesting of theα-Fe₂O₃ compared with the surface-covered TiO₂,which contributes to the better charge-transfer ability and enhanced PEC performance.The exposed{001}facets of TiO₂ in the E-Sn-Fe₂O₃/TiO₂ photoanode also facilitate the charge transport and improve the PEC performance.（3）The Ti₃C₂T_X/g-C₃N₄ composite photocatalyst with visible light response was prepared by a simple mechanical mixing strategy.The effects of different Ti3C2TX contents on the g-C3N4 were investigated.The results indicate that when the mass ratio of Ti3C2TX to g-C3N4 is 3:10,the activity of photocatalytic hydrogen production can reach the maximum value of 829.2μmol/g/h,which is significantly higher than pure g-C₃N₄.