Ultrathin In₂O₃ Nanosheets:Preparation,Modification And Photoelectrochemical Performance

In₂O₃ semiconductor has been widely used in many fields owing to its unique properties,such as high light transmittance,low resistivity,and high catalytic activity.As a material for photoelectrochemical（PEC）water splitting,although In₂O₃ well satisfies the band gap requirement for the direct split of water owing to its band edge positions straddling the reduction and oxidation potentials of water,its wide direct band（3.55³.75eV）gap results in poor absorption of visible light,which severely restricts its application in PEC water splitting.It is well known that the properties of nanomaterials are largely dependent on their morphology and size.Therefore,it is very important to prepare nanostructured In₂O₃ with controllable morphology and size.Ultrathin two-dimensional nanomaterials have been widely used in the PEC water-splitting owing to their large specific surface area,unique electronic structure,and high carrier mobility.In this paper,ultrathin In₂O₃ nanosheets（UINS）with controllable morphology were prepared and modified.The main research content is as follows:（1）A new In₂O₃ precursor was prepared by sol-gel method,and then UINS was obtained by air heat treatment.The structure of UINS was analyzed by a series of characterizations,and the effect of sodium hydroxide concentration and calcination temperature on the PEC performance of UINS was explored.When the concentration of sodium hydroxide was 0.1 mol/L,the band gap of the prepared UINS was significantly lower than that of the pure In₂O₃.When the calcination temperature was 400°C,the highest photocurrent density of UINS was 0.14 mA/cm² at the external bias of 1.23V vs.RHE.（2）The In₂O₃ precursor and graphene（GR）were fully sonicated in anhydrous ethanol.The composites of In₂O₃ and GR were successfully prepared after centrifugation,drying,and air calcination.The structure of the material was analyzed by a series of characterizations,and the effect of GR content in the composites on the PEC performance of the In₂O₃/GR composites was investigated.The experimental results indicated that the morphology and structure of In₂O₃ did not change in the as-prepared In₂O₃/GR composites.In₂O₃ and GR interacted strongly during the composite process,and the In-O-C chemical bond may be formed,which further reduced the UINS band gap,increased the absorption of light,promoted the migration of photogenerated carriers,inhibited the recombination of photogenerated electrons and holes,and thus effectively improved the PEC performance.When the content of GR is 1wt%,the highest photocurrent density of the In₂O₃/GR composites is 0.21 mA/cm² at the external bias of1.23V vs.RHE,which is 1.5 times that of UINS.