| Renewable energy is an important guarantee and prerequisite for sustainable development.The conversion of solar energy into pure,storeable hydrogen using photoelectrochemical（PEC）water splitting cell is efficient and has a wide range of potential applications.However,there is a key problem in PEC water splitting to produce hydrogen,that is,how to research and develop semiconductor photocathode materials with efficient optical absorption and PEC performance.Because of its small optical absorption band gap,large optical absorption coefficient,suitable hydrogen evolution potential,good carrier migration rate,relatively long lifetime,and stable chemical properties,delafossite Cu Fe O 2 has emerged as one of the most appealing target materials among the many new photocathode materials developed.Although CuFeO2 has promise for PEC water s plitting,the performance of its photocathode is still lower than anticipated.The primary causes for its poor performance are higher photogenerated electron-hole pair recombination and poorer photogenerated carrier mobility.Therefore,from the point of v iew of material surface and interface structure design,this article focuses on the design and regulation of crystal plane structure and heterogeneous int erface in order to improve the PEC performance of Cu Fe O2 and expand the application of Cu Fe O 2 in PEC technology.The following is a summary of the primary study contents and results:（1）CuFeO2 samples with different crystal plane orientation and morphology were prepared by changing hydrothermal reaction time,ultrasonic time and adding surfactant.Compared with the cube Cu Fe O 2composed of（012）crystal plane and the cone Cu Fe O2 sample composed of（001）crystal plane,the Cu Fe O2 nanosheets with 83.36%exposure ratio of（001）crystal plane show the highest photocurrent density（5.3μA/cm2）,that is,the exposure of appropriate（001）polar crystal plane and the formation of nanometer size are very important to the PEC performance of Cu Fe O 2.The reason for this is that the（001）crystal plane is a polar surface,and increasing its exposed area benefits the surface polarization effect,which improves the separation efficacy of photogenerated electron-hole pairs.（2）A series of CuFeO 2 hexagonal nanosheets with different thicknesses were prepared by a simple one-pot hydrothermal method.The larger the width and the smaller the thickness of Cu Fe O 2 nanosheets are,the greater the photocurrent density is.The photocurrent density of Cu Fe O 2 nanosheets with the highest aspect ratio（8μA/cm2）is about 6 times higher than that of Cu Fe O2 nanosheets with the lowest aspect ratio（1.4μA/cm2）.With the increase of the width of Cu Fe O2 nanosheets,the contribution of the surface polarization effect of{001}crystal plane increases,and the built-in electric field intensity of the surface polarity effect of{001}crystal plane increases sharply and the diffusio n distance of photogenerated carriers decreases with the decrease of the thickness of CuFeO 2 nanosheet.（3）Through the core-shell heterostructure construction strategy of close interface contact,the core-shell heterostructure of V O-Cu O@Cu Fe O2with oxygen-containing vacancy Cu O as shell and Cu Fe O 2 nanosheet as core was successfully prepared.After optimizing the annealing time,annealing temperature,layer number and Cu Fe O 2 composition content of the thin films,the optimum photocurrent density of VO-Cu O@Cu Fe O2 can reach 68μA/cm2,which is nearly 9 times higher than that of the original Cu Fe O2 nanosheets.The interface electric field provides the necessary driving force,and the interface Cu-O bond forms a direct charge transfer channel between VO-Cu O and Cu Fe O2 nanosheets,which further accelerates the charge transfer process.In addition,abundant oxygen vacancies also help to enhance optical absorption and accelerate optical carrier separation.These elements govern efficient PEC performance of the oxygen-rich vacancy VO-CuO@CuFeO2,which offers a fresh perspective on how to boost the effectiveness of photocatalytic materials. |
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