Study On Ni-based Bifunctional Co-catalyst Modification Of TiO₂ Nanotube Arrays And Photoelectrocatalytic Performance

TiO₂ nanomaterials have excellent chemical stability and high reactivity,and become a star material for water splitting catalysts.TiO₂ nanotube has become the first choice because of its highly regular and ordered structure,large specific surface area,and can provide channels for carrier transportation.However,the wider band gap and the faster photogenerated electron-hole pair recombination rate restrict its development and application.In this paper,Ni-based co-catalyst is selected to modify the TiO₂ nanotube arrays and the performance of photoelectric catalytic water splitting is evaluated to solve the above problems.The main progress includes the following three aspects:（1）The highly regular and orderly TiO₂ nanotube arrays（A-TNTAs）are prepared by simple anodic oxidation.After annealing,the amorphous TiO₂ nanotube arrays are completely transformed into anatase phase（TNTAs）,showing excellent photoelectric catalytic performance.The Ni₂P oxygen evolution promoter is modified on the anatase phase TiO₂nanotube arrays by electrodeposition（TNTAs/Ni₂P）.The characterizations of the Scanning electron microscopy（SEM）,X-ray diffraction（XRD）and Raman spectroscopy（Raman）show that the loading of Ni₂P does not change the morphology and structure of TiO₂ nanotubes,but the loading of Ni₂P oxygen evolution co-catalyst can significantly improve photoelectrocatalytic performance of the TiO₂ nanotubes arrays.The support of Ni₂P co-catalyst is beneficial to capture photo-generated holes and promote the separation of photo-generated charges and holes.（2）TiO₂ nanotube arrays loaded with Ag,Ni and Ag-Ni were prepared by light deposition（TNTAs/Ag,TNTAs/Ni and TNTAs/Ag-Ni）.The support of Ag-Ni bimetallic co-catalyst does not change the morphology and structure of TNTAs.XPS analysis proves that Ag exists in the form of elemental metal and Ni exists in two forms of elemental metal and Ni²⁺.The photoelectrochemical performance test shows that the loading of single metal Ag and Ni will improve the photocatalytic performance of TNTAs.Compared with the single metal loading,the co-loading of Ag-Ni increases the carrier density and suppresses the recombination rate of photogenerated electron-hole pairs,which is beneficial to the improvement of photoelectric catalytic performance.（3）Ni,Ni₂P and Ni/Ni₂P supported TiO₂ nanotube arrays（TNTAs/Ni,TNTAs/Ni₂P and TNTAs/Ni/Ni₂P）were prepared by electrodeposition.The loading of Ni/Ni₂P dual-function co-catalyst does not change the morphology and structure of TNTAs.The loading of Ni oxygen evolution co-catalyst and Ni₂P hydrogen evolution co-catalyst will improve the photoelectric catalytic performance of TNTAs.The loading of Ni/Ni₂P bifunctional co-cocatalyst exhibits the highest photocurrent density relatively,which indicates a higher photoelectric catalytic performance.The fluorescence test and the kinetic test proved that the photo-generated electron transfer rate increased due to the existence of the work function,and inhibited the recombination of photo-generated electron-hole pairs to a certain extent,which is beneficial to the improvement of photoelectric catalytic performance.