Interface Stnicture Regulation And Hydrogen Production Application Of Cu-In-Zn-S Quantum Dots Based Photocatalysts

Hydrogen energy,an efficient and clean energy,has been a hot topic for relieving both environmental pollution and energy crisis.Photocatalytic hydrogen production can attach an effective energy conversion from sustainable solar energy into storable hydrogen energy in the photocatalytic water splitting system,which is a promising approach for the utilization and storage of solar energy.It is important for the effective utilization of solar energy to development visible-light-driven photocatalysts.Visible-light-driven?-?-?quantum dots?QDs?have been a hot topic for photocatalytic hydrogen production due to the substantial advantages of tuning bandgap,massive active sites,broad absorption,and quantum confinement effect.The photocatalytic activity and stability of hydrogen evolution for phtocatalysts must meet the standard of scale application.However,photocatalytic activity and photostability still need to be improved as a result of the photocorrosion effect for sulfide materials.In this work,photocatalytic performance including activity and stability of Cu-In-Zn-S QDs is optimized through the optimization of band structure and the regulation of interface.The defects can be tuned by controlling the contents of doping.Loading various kind of cocatalyst and increasing the interaction of interface result in the effective photocatalytic activity due to the increasing separation of electron-hole pairs,which lays a foundation for scale application.The major research work in this paper are as follows:?1?A set of Cu-In-Zn-S QDs with different quantities of Cu were prepared with one-step hydrothermal method.The influence for the Cu component contents on band structure and activity of photocatalytic hydrogen production was investigated.And the mechanism that cocatalyst affects the photocatalytic performance of photocatalysts with high doping Cu contents is the focus of research.The bandgap decreases from wide gap of 2.90 eV to narrow gap of 1.98eV with increasing Cu content.The QDs can achieve excellent photocatalytic activity for hydrogen production by increasing the Cu content in the photocatalytic system without cocatalyst.Yet,the potential development of visible-light-responsive photocatalyst is easily limited due to abundant recombination centers from Cu defect that results in the reduction of photocatalytic performance.Cocatalyst Pt loading promote both the activity for photocatalytic hydrogen production and the tolerance of Cu.The competition effect between cocatalyst-induced the separation of charge carriers and Cu defect-induced the recombination of electron-hole pairs bring outstanding activity and enhanced the tolerance of Cu.These results provide a new sight for optimizing the photocatalyst with narrow bandgap.?2?Cheap MoS₂ is further introduced the photocatalytic system as cocatalyst due to the high cost of the novel metal Pt.Cu-In-Zn-S QDs/MoS₂ composites were prepared throuth in situ growth of molybdenum sulfide on the surface of QDs.The effects of temperature and the loading contents of MoS₂ on the structure of composites and the photocatalytic performance were deeply discussed.The best photocatalytic activity of Cu-In-Zn-S QDs/MoS₂ composites is 7.8 times higher than bare QDs due to the balance of catalytic effect and shading effect through controlling the content of MoS₂ loading.The activity and stability for hydrogen?H₂?production are dramatically promoted with the loading MoS₂ that may contribute to the effective separation of charge.The best activity(19.83 mmol h^-1g^-1)is achieved by Cu-In-Zn-S QDs/MoS₂-12%composites in the presence of ascorbic acid as sacrificial agents,which is close to the best performance in this field under the condition of simplifying the structure and preparation methods dramatically.The photocatalytic activities of composites are promoted and then decreased with the increasing temperature.The increasing temperature of heat-treatment facilitates the interaction of interface,but high temperature can result in the decreasing photocatalytic activity for water splitting due to serious agglomeration of QDs.The connection of 0D/2D materials and the interface structure regulation have a directive meaning for building effective photocatalysts based on QDs.?3?In order to the scale application of photocatysts,the prepared approach of Cu-In-Zn-S QDs/MoS₂ composites is further optimized.Cu-In-Zn-S QDs functionalizing with molybdenum sulfur clusters are successfully prepared through facile hydrothermal approach in which the molybdate are ligand and molybdenum source.The influence of molybdenum sulfur clusters on the structure and performance of QDs is investigated.The QDs modified with molybdenum sulfur clusters?Mo/In=0.1/1?carriy out best activity(1242.7?mol h^-1g^-1)that is 2.6 times higher than bare QDs.Molybdenum sulfur clusters act as the capture center of electron to dramatically enhance the transform of charge carriers.Photoluminescence spectra and electrochemical impedance spectroscopy?EIS?effectively illustrate the fast transformation of photoexcited electron and the suppressed recombination of charge carriers about the QDs through loading the molybdenum sulfur clusters.The synthesis of Cu-In-Zn-S QDs/molybdenum sulfur cluster in photocatalytic system is greatly simplified by introducing the molybdate as the ligand in situ.The incorporation of molybdenum sulfur clusters through functionalizing in situ provided a new perspective and opportunity for the design and macroscale preparation of efficient colloidal photocatalysts based on QDs.