ZnO/CeO_(2)/carbon xerogel composites with direct Z-scheme heterojunctions:Enhancing photocatalytic remediation of 4-chlorophenol under visible light

This paper aims to create visible light driven ternary photocatalysts using zinc oxide(ZnO),cerium(IV)oxide(CeO_(2)),and carbon xerogel(CX) as constituent materials.The use of CeO_(2) is based on the creation of direct-Z-scheme heterojunctions with the ZnO and the consequent diminishing of charge recombination,whereas the carbon xerogel inclusion is predicted to minimize bandgap energy,decrease electro n-hole reco mbination,and boost specific surface area.Furthermo re,the choice of the black-wattle tannin as a carbonaceous precursor was targeted at the development of an environmentally friendly and affordable composite.The existence of the hexagonal phase of zinc oxide and cubic structure of the cerium(IV) oxide in the ternary material was confirmed by X-ray diffractometry and X-ray photoelectron spectroscopy,with the latter also suggesting chemical bonding between the ZnO and the CX due to the creation of zinc oxycarbide complexes.The inclusion of the carbon xerogel provokes a significant modification in the morphology of the ternary material,resulting in an increased surface area and smaller particle aggregates.The CX/ZnO-CeO_(2) ternary composite obtains the highest photocatalytic efficiency among all the materials studied,degrading 100% of 4-chlorophenol under simulated sunlight and 68% under visible radiation,after 5 h.The increased photocatalytic activity can be attributed to the formation of direct Z-scheme heterojunctions between the semiconductors,higher visible light response,and higher specific surface area,as evidenced by the results obtained by active radical scavenging,chronoamperometry,diffuse reflectance spectroscopy,and N_(2) adsorption-desorption isotherms.

Ni_(3)B modified BiVO_(4) photoanodes for enhanced photoelectrochemical water splitting:The key role of Ni_(3)B on reducing the water oxidation barrier

Bismuth vanadate(BiVO_(4),BVO)as a promising photoelectrode has been received great attention for photoelectrochemical(PEC)water splitting.However,the slow oxidation kinetics on the surface of BiVO_(4)limited the PEC water splitting efficiency.Herein,nickel boride(Ni_(3)B,NB)nanoparticles,generally used in electrocatalytic field material,were modified on the surface of BiVO_(4)photoelectrode as an efficient cocatalyst to accelerate the oxygen evolution reaction.The as-prepared BVO-NB-5P photoelectrode exhibits a remarkable photocurrent density of 1.47 mA·cm^(−2)at 1.23 V versus the reversible hydrogen electrode(RHE)under air mass(AM)1.5 G illumination,which is about 2.8 times higher than the bare BiVO_(4)photoelectrode,and its water splitting rate is 11.3 times higher than bare BiVO_(4).The PEC studies reveal that the spin coated Ni_(3)B crystal cocatalyst could effectively reduce the water oxidation barrier,and improve the surface charge injection efficiency to 94%,which could boost the photogenerated holes reaction to enhance the PEC performance of BiVO_(4)photoelectrode.