| Photocatalytic technology is a promising technology for renewable energy development and environmental pollution control.During the photocatalytic process,the activity of catalyst directly determine its efficiency.Constructing heterojunction can expand the light absorption range and promote interfacial charges separation of single semiconductor photocatalyst to some extent.Nevertheless,traditional heterojunction still suffers from low interfacial charge separation,weakened redox ability and poor surface reaction activity,which can be ascribed to its high energy potential barrier,inappropriate charges transfer path and limited surface active site exposion.To solve these shortages,this work adopts serval methods,such as preparing vertical nanosheets to improve the exposion of surface active sites,optimizing contact facet to minish interfacial energy potential barrier,constructing Z-scheme to preserve the redox ability of photogenerated charges,and coupling Fenton technique,to improve the photocatalytic performance of heterojunction photocatalysts.The main works and related results are shown as follow:(1)TiO2-MoS2 heterojunction with few-layer MoS2 nanosheets vertical growth on porous TiO2 was prepared via an in situ hydrothermal method.The microstructure of as-prepared photocatalyst was characterized by TEM analysis.It was revealed that MoS2 nanosheets randomly stood on the surface of porous TiO2 has a thickness less than 3 nm(1-4 layers),which provides high denisty unsaturated S atom at the edge of MoS2 as activity sites.The photocatalytic H2 evolution performance of TiO2-MoS2 was measured under simulated solar light irradiation with Na2S and Na2SO3 as sacrificial agent.The results showed that H2evolution rate on TiO2-MoS2(60 wt%)was 897.5 μmol·h-1·g-1,which was much higher than those o=porous TiO2(negligible H2 was detected),MoS2(481.3 μmol·h-1·g-1)and the sample mechanical mixture of TiO2 and MoS2(TiO2+MoS2,39.2 μmol·h-1· g-1).(2)BiVO4-Au@CdS Z-scheme photocatalyst with Au@CdS selective deposition on BiVO4{010} facet was prepared by a two-step photoreduction approach.Meanwhile,c-BiVO4-Au@CdS prepared by random deposition of Au@CdS on the whole surface of BiVO4({010}or {110} facet)was selected as control group.Their photogenerated charge separation performances were investigated by photocurrent and photoluminescence(PL)tests.Results indicated that BiVO4-Au@CdS exhibited better charge separation ability than that of c-BiVO4-Au@CdS.Moreover,4-Nonylphenol degradation experiment showed that the kinetic constant of 4-NP degradation on BiVO4-Au@CdS Z-scheme was 0.043 min-1,which was 1.48 times higher than that of c-BiVO4-Au@CdS(0.029 min-1).This can be attributed to that the BiVO4-Au@CdS prepared by selectively deposited Au@CdS on BiVO4{010} facet favor the photogenerated electrons transfer from BiVO4 to the Au NPs,which further improving the interfacial charges separation efficiency.(3)By controlling the contact facet between TiO2(or Cu2O)and Pd,four Z-scheme photocatalysts,TiO2{001}-Pd-Cu2O{100},TiO2{001}-Pd-Cu2O{111},TiO2{101}-Pd-Cu2O{100} and TiO2{101}-Pd-Cu2O{111} were obtained.DFT calculation was carried out to simulate their interfacial energy band structures,and TiO2{001}-Pd-Cu2O{100} was supposed to possess optimal interfacial energy band structure than others.Photocurrent,PL,electrochemical impedance spectroscopy(EIS)and open-circuit voltage decay(OCVD)tests demonsted TiO2{001}-Pd-Cu2O{100} has best charge separation performance.Moreover,phenol degradation results indicated the degradation rate of phenol on TiO2{001}-Pd-Cu2O{100} was 0.088 min-1,which was 1.26,1.22 and 2.05 times higher than those of TiO2{001}-Pd-Cu2O{111}(0.070 min-1),TiO2{101}-Pd-Cu2O{100}(0.072 min-1)and TiO2{101}-Pd-Cu2O{111}(0.043 min-1).TOC removal rate proved TiO2{001}-Pd-Cu2O{100}possessed efficient mineralized property with TOC removal rate of 76.5%,which was much higher than those of TiO2{001}(32.1%)and Cu2O{100}(2.9%),and even higher than the sum of TiO2{001}-Pd(57.0%)and Pd-Cu2O{100}(5.9%).(4)WO3 and Fluorine doped porous carbon(FPC)were synthesized via first hydrothermal growth and then high temperature calcination process.Through optimizing the energy band structures between WO3 photoanode and FPC cathode,an efficient WO3-FPC photoelectrochemical(PEC)system was constructed.The H2O2 generation performance of this system was evaculated under different operation conditions.As a result,the WO3-FPC system exhibited optimal H2O2 production rate of 0.75 mmol·L-1·h-1 with FE of 75%(under the condition of 1.0 V anode bias,solution pH=1,FPC loaded amount of 0.5 mg·cm-2).The in situ generated H2O2 can be further utilized for phenol,bisphenol A and atrazine degradation by introducing Fe2+to construct PEC-Fenton systen.Results proved that all above pollutants can be degraded more than 90%and mineralized 40%-50%.Electron paramagnetic resonance(EPR)technique demonstrated that·OH generated via PEC-Fenton process enhanced the PEC degradation performance of WO3 photoanode. |
