Preparation Of Bimetal-driven Z-Scheme Photocatalysts For Photocatalytic Overall Water Splitting

Z-scheme photocatlaysts have exhibited a broad application prospect on photocatalytic overall water splitting.However,photo-generated electrons and holes are recombined as they inclined to transport to the carriers'transmission media thermodynamically.It causes the low separation efficiency of high energy photo-generated carriers and low solar-to-hydrogen energy conversion efficiency of Z-scheme photocatlaysts.For this problem,we demonstrate a conceptually new approach:changing the structure of Z-scheme photocatlaysts from photocatlaysts/metal/photocatlaysts to photocatlaysts/metal A/metal B/photocatlaysts.The contact of two kinds of metals forming contact potential difference,we apply the contact potential difference to separate the high energy photo-generated carriers to split water in photocatalysts and attract the low energy photo-generated carriers into the metal to make recombination.Thus,the selective separation and recombination of photo-generated carriers could be realized,when using the bimetal to control their transportation.In this work,we prepared the bimetal-driven Z-scheme photocatalytic materials,studied their energy band structures and investigated their photocatalytic overall water splitting performances.Finally,the excellent solar to hydrogen?STH?conversion efficiency was obtained by this structure.The specific research contents and conclusions are as follows:1.The TiO₂/metal nanoparticles(P₂₅/Ag)were synthesized by commercial TiO₂nanoparticles(P₂₅)with good photocatalytic hydrogen production performance using impregnation method;the graphene oxide was reduced as graphene by microwave reduction with semi-metallic property.The graphene was encapsulated on the tungsten oxide?WO₃?with photocatalytic water oxidation property,finally,forming the WO₃/graphene/Ag/P₂₅photocatalytic composite by ultrasonication and lyophilization procedures.Photocatalytic experiments and theoretical calculations showed that this structure does improve water splitting performance in pure water,with hydrogen generation rate of 1.918?mol cm^-22 h^-11 and0.118%of STH efficiency,10.65 times higher than that of WO₃/P₂₅.2.P₂₅/Ag and WO₃ powders were coated on opposite sides of graphite carbon paper?C?,respectively.Then Z-scheme photocatalytic materials TiO₂/Ag/C/WO₃ was prepared by nitrogen annealing at 400? for 1 h.Z-scheme photocatalytic materials:TiO₂/Ag/C/WO₃exhibited high photocatalytic performance in pure water,with hydrogen generation rate of1.198?mol cm^-22 h^-11 and 0.095%of STH efficiency,9.98 times higher than that of the hybrids:TiO₂/WO₃.3.CdS and BiVO₄ powders were coated on opposite sides of graphite carbon adhesive attached to the gold foil?C/Au?,respectively.Then Z-scheme photocatalytic materials CdS/Ag/C/BiVO₄ was prepared by nitrogen annealing at 400?,and the Z-scheme photocatalytic materials CdS/Ag/C/BiVO₄ had the superior photocatalytic water splitting performance in pure water,with hydrogen generation rate of 4.458?mol cm^-22 h^-11 and 0.354%of STH efficiency.