First-principles Calculations On Excited-State Dynamics In Plasmon-driven Photocatalytic Reaction

Based on the goal of carbon peaking and carbon neutralization in our country,carbon reduction and decarbonization technology will become the focus of research and development in the field of energy and environment in the short term,in which the absorption,reduction and conversion of carbon dioxide and the generation and utilization of hydrogen energy have attracted widespread attention.In addition,the confined electrons on the surface of noble metal nanoparticles such as gold,silver and copper upon illumination will collectively oscillate,resulting in the localized surface plasmon resonance(LSPR),which usually exhibits distinct properties such as extended carrier lifetime,tunable resonance energy,ultrafast carrier dynamics and enhanced optical absorption.Therefore,these materials are also called plasmonic nanomaterials.Based on these properties,plasmonic nanostructures can be used as an excellent platform for the exploration of light-matter interactions in a wide range of applications such as photodetection,photovoltaics,surface-enhanced Raman spectroscopy,photoelectrochemistry,and photocatalysis.In particular,plasmon-driven photocatalytic reactions of molecules adsorbed on metal nanostructures have sparked considerable attention in chemical and solar energy conversions in recent years.However,due to the complex interactive dynamics of the excited carriers between plasmonic nanomaterials and the adsorbates,the underlying mechanism during these processes remain elusive and needs to be further investigated.In this dissertation,taking photoreduction of carbon dioxide(CO2),photolysis of ammonia(NH3),and water splitting as typical examples,we investigate the underlying mechanism in the plasmon-driven photocatalysis process via the analysis of ultrafast non-adiabatic molecular dynamics and excited carrier dynamics in the framework of ab initio time-dependent density functional theory(TDDFT).The main contents are listed as follows:1.Plasmon-driven CO2 photoreduction on silver atom chain and the corresponding charge transfer mechanism.Firstly,via the selection of adsorption configuration and corresponding light response upon photoexcitation,we reveal that photon energy and laser intensity can regulate the reduction rate of carbon dioxide,and the reaction process is driven by local surface plasmons;Secondly,it can be proved that the reaction process is driven by charge transfer after plasmon excitation by analyzing the charge transfer under different field strength;Finally,we demonstrate that the indirect charge transfer mechanism plays a dominant role in the photoreduction process through the analysis of time-dependent occupation number and transition coefficient.2.The interplays of different charge transfer processes in the plasmon-driven CO2 photoreduction on the surface of silver nanoclusters.At first,we unravel that the excitation of asymmetric vibration mode and bending vibration mode of CO2 molecule is important in the decomposition process via the Flourier transform analysis of timedependent change bond length under laser pulse;In addition,through the analysis of non-adiabatic molecular dynamics under different laser intensity,the nonlinear relationship between laser intensity and reaction rate is obtained;To the end,we prove that the nonlinear relationship is due to the delicate synergy and transition between indirect and direct charge transfer mechanisms via the ultrafast excited-state carrier dynamics.These findings provide new insights for carbon dioxide photoreduction and facilitate the design of efficient plasmon-driven photocatalysts.3.Plasmon-driven photodecomposition of NH3 via intramolecular charge transfer on the surface of silver nanocluster.Through the study of ultrafast diabatic molecular dynamics and excited state carrier dynamics at the atomic scale and femtosecond time scale,we prove that the intramolecular charge transfer driven by local surface plasmon plays a dominant role in the photolysis of ammonia,while the direct or indirect charge transfer plays a secondary role.Meantime,this photolysis phenomenon does not depend on the size and shape of nanoparticles.In addition,other than the polarization direction of the light field,incident photon energy and laser intensity,the phase of the laser pulse can also take a crucial role in tuning the reaction rate via modulating the dynamics of excited-state carriers.These results provide a new decomposition pathway for NH3,and offer new insights for the application of ammonia in hydrogen storage and fuel cells.4.Plasmon-induced water splitting on Ag-alloyed Pt single-atom catalysts.First,by comparing the light absorption properties of the catalyst with and without monatomic platinum,we reveal that the introduction of monatomic platinum enhances the interaction between the metal particle and water molecule;Second,through the comparison of molecular dynamics and charge transfer between the two systems,it can be proved that monatomic system can enhance the charge transfer during the reaction process;Furthermore,by comparing the changes of time-dependent occupation in the two systems,we prove that the introduction of monatomic platinum opens more charge transfer channels and realizes the effective photolysis of water.In summary,based on the investigation of the microscopic reaction dynamics mechanism of the photocatalytic reaction processes in the above systems,we provide new sights on the plasmon-driven photocatalytic reaction,which is expected to be instrumental in the theoretical design and experimental fabrication of highly efficient plasmon-driven photocatalysts.