Photo/Thermal Synergic Hydrogen Generation And Mechanism With Full Spectrum Nano-volumetric Absorption

Solar energy is the most thriving renewable energy in recent years,thanks to its wide distribution,abundancy,and accessibility.Given its rapid growth,the utilization of solar energy is still bottlenecked by low efficiency and high cost.This results from poorly treating the energy capacity of concentrated solar photons by mainstream solar conversion pathway,thus in principle constraining the improvement of efficiency.To tap the potential of the full spectrum concentrated photon energy,the breakthrough can be either allocating each solar photon to its most suitable conversion pathway or raising a new and more rational conversion pathway.This work is intended for such cause and is supported by a Basic Science Center Program and two Major Projects from the NSFC.This work began with the nanoscale selective sunlight extinction,absorption,and conversion of solar photon energy,designed several full-spectrum utilization methods,and carried out experiments on them.The research scope,procedure and main findings are:(1)The microscale selective absorption and conversion mechanism of solar photon energy.Mie theory and finite element method were used for modeling spherical and arbitrary shape nanoparticles,where the multi-particle absorption model was raised.The photon-electron-phonon energy conversion expressions were raised,by which the wavelength and morphology dependence of metallic nanospheres were determined.Integrating across the photon frequency,the photon energy expression was related with solar spectrum energy.(2)A volume absorption solar energy utilization method was proposed based on the spectrum selection of plasmonic Ag nanofluid,where the absorbed ultraviolet and infrared spectra are used as reaction heat for thermochemistry while the transmitted visible and near-infrared spectra are for photovoltaics.Modeling results show that increasing the concentration and optical thickness reduces the optical loss,giving rise to the solar-chemical efficiency.However,increasing the size of the nanoparticles aggregates the optical scattering loss,hence the nanofluid absorber works better in photo-thermal conversion only when the diameter is smaller than 40 nm.Then,the thermochemical conversion was analyzed for the absorbed 300?1100 nm wavelength.Introducing the spectrum response,the sunlight-to-electric-current conversion performance was analyzed and compared,indicating that the ultraviolet-infrared is better for thermochemistry-SOFC while the visible-near-infrared is better for the photovoltaics.(3)An experiment on full-spectrum sunlight conversion was done by integrating a selective absorption photothermal synergic reaction with photoelectric conversion.Through electromagnetic finite element simulation,the light-matter interaction is revealed for designing the Au-TiO2 nanoparticle.Then,the transmitted spectral band and energy were measured for the selection of photovoltaic cell.Photocurrent measurement was done for Au-TiO2 under solar concentration conditions and explained by finite element method simulation.The experiment was conducted under the solar concentration ratio of 1?15 and the catalyst concentration of 0.1?1.0 g·L-1.Results show that the photothermal synergic catalyst here generated H2 30?50%faster than earlier reported work.When compared with solar thermochemistry,this work possibly reduced the input solar concentration ratio by 30?45 for the same H2 generation rate.The reason for such advantage is due to the reduced recommendation loss and light scattering loss by selectively absorbing the most suitable ultraviolet and infrared spectra.On the photoelectric side,the transmitted spectra have reduced thermal relaxation thus the photovoltaic efficiency is maintained at over 30%.The energy loss from light transmission,scattering and photovoltaic relaxation were reduced,thus the proposed method has more potential for solar energy conversion.(4)The concept of concentrated solar photochemical looping water splitting is proposed.High energy concentrated solar photons are used to reduce the oxygen carrier material to form light-induced oxygen vacancies.Then,the low energy photons energized the water oxidation process on oxygen vacancies,releasing H2.The author developed the photochemical looping batch and flow reactor,which were verified by the Cu-TiO2 at a decent H2 production rate of 242 ?mol·h-1·gcat-1,30%higher than reported photochemical cycle.Then,the author designed new material considering low activation energy and high mobility of the transport of bulk phase oxygen ions.A series of promising materials were targeted like CuFeO2,V-Bi2O3,In-BiOCl and LaTiON.To explain the localized heating effect in photothermal synergic reaction and photochemical looping,this work also investigated the photon/phonon interaction at nanoscale.Using finite element method and DFT simulation,the Pd@Nb2O5 nanoparticle was studied in its photon/phonon conversion.