| Photoelectrochemical(PEC)water splitting is expected as one of the most promising technologies to address the challenges of impending worldwide energy consuming and associated climate change resulting from combustion of fossil fuels.Owing to their high aspect ratio,large specific surface area,and excellent electronic or ionic charge transfer properties,1D TiO2 nanostructured materials are widely used in PEC water splitting.However,as a kind of wide band gap material,TiO2 has a low utilization of the full solar energy spectrum,limiting its solar-to-hydrogen efficiency.To address this issue,TiO2 based materials with excellent properties were prepared by constructing heterojunction and loading cocatalyst,which could applied in the field of PEC water splitting.The main innovative research results are as follows:(1)TiO2@Co-C3N4 nanorod array was prepared by drop-coating and hydrothermal method.The successful coordination between Co atom and g-C3N4 was proved by XPS,FTIR,EDS and UV-Vis DR.The PEC performance of TiO2@Co-C3N4 nanorod array can be tuned by the amount of Co-C3N4 coated.When the amount of Co-C3N4 reached about 0.75 ?g/cm2,the PEC performance of TiO2@Co-C3N4 reached maxium.At this time,the content of Co atom was about 1.47×10-3 ?g/cm2.The results show that the photocurrent density of TiO2@Co-C3N4 nanorod array reach 1.79 mA/cm2 at 1.23 VRHE,which is about 2.3 times of that form TiO2@g-C3N4.And the PEC device based on TiO2@Co-C3N4 nanorod array has good stability and the photocurrent density remain no decline after 10 hours of continuous operation.The Mott-Schottky and DPV curves demonstrate that a matching n-n heterojunction was constructed between g-C3N4 and TiO2,Co atoms coordinated with g-C3N4 maybe act as a co-catalyst for water oxidation,and a possible mechanism is proposed for water oxidation based on careful analysis of the detailed results.The holes photogenerated by electrons exciting oxidize Co atoms from Co? to Co? and Co?,and these high active cobalt species accelerate the kinetics of water oxidation.In addition,Co-C3N4 not only can promote the charge transfer but also improve the overall energy conversion efficiency of the PEC device.(2)A photoelectrochemical device was achieved by interfacial self-assembly of macrocyclic ?-conjugated copper phthalocyanine(CuPc)on surface of TiO2 nanorod arrays for the first time.The PEC performance of TiO2@CuPc nanorod arrays varied with the electrodeposition time of CuPc and the PEC performance of TiO2@CuPc reached maxium when the electrodeposition time is 60 s.At this stage,the content of Cu atom is about 27.1?g/cm2,and the the surface atom ratio of Ti to Cu from the optimized sample is about 30:1.The photocurrent density of the elegant TiO2@CuPc nanorods photoanode reaches 2.40 mA/cm2 at 1.23 VRRHE under the illumination of 100 mW/cm2 from AM 1.5G sun simulator,which is 2.4 times higher than that of the pure TiO2.At the same time,the photoelectrochemical device constructed through this strategy has good stability and the photocurrent density remain almost no decline after continuous operation.The Mott-Schottky and LSV curves demonstrate that CuPc act as a co-catalyst for water oxidation and a possible mechanism is proposed for water oxidation based on careful analysis of the detailed results.The holes from VB of TiO2 photogenerated by electrons exciting are consumed by a process in which Cu? is oxidized to Cu? and Cu?,and then oxygen was produced through water oxidation by these high active species.CuPc is considered to be a fast redox mediator to reduce the activation energy of water oxidation in and effectively promote charge separation at the same time. |
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