| The proposal of carbon neutrality and zero carbon emissions has stimulated the demand for renewable energy.Renewable energy sources include solar energy,wind energy,geothermal energy,and nuclear energy,which have minimal environmental impact.Among them,solar energy is one of the cleanest energy sources.Photovoltaic power generation and photocatalytic water splitting are successful examples of utilizing solar energy.Photovoltaic power generation converts sunlight into electricity through the photovoltaic effect,without the need for fuel combustion and greenhouse gas emissions.Photocatalytic water splitting uses solar energy to decompose water into hydrogen and oxygen,with the produced hydrogen being used as fuel without harmful gas emissions.Both are clean and efficient ways of utilizing solar energy.To fully utilize solar energy,it is necessary to improve the performance of light-absorbing materials.Therefore,this study developed a lightabsorption-oriented structure prediction method based on the CALYPSO software,providing structure search strategies for different requirements,and applied it to the search for solar cell materials and photocatalysts for water splitting.The important research content and conclusions of this study are as follows:1.Design of light-absorption-guided structure prediction StrategyTo more efficiently utilize solar energy,it is crucial to find light-absorbing materials with excellent performance.Different applications of solar energy have different requirements for light-absorbing materials.In addition,within the same application scenario,the design requirements for light-absorbing materials are also diverse.In order to obtain optimal solutions that meet multiple objectives,this study developed a light-absorptionoriented structure prediction method using multi-objective algorithms based on CALYPSO.These methods include flat-band-oriented structure design methods,structure design methods targeting reduced electron-hole recombination,and structure design methods targeting high electron-hole mobility.Through these methods,we can find semiconductor materials with specific bandgaps and band edge shapes.2.Application of light-absorption-guided structure prediction Strategy in solar cell materialsPhotovoltaic power generation is a clean and efficient method of utilizing solar energy.However,most of the current commercial solar cells are made of silicon,which does not fully meet the requirements for solar cell materials.Firstly,silicon has an indirect bandgap of 1.1 e V,which leads to low efficiency in light absorption.In addition,silicon has a direct bandgap width of 3.4 e V,resulting in a low absorption coefficient in the solar spectrum,which is not conducive to the utilization of solar energy.Therefore,it is necessary to find structures suitable for solar cell materials.Two-dimensional carbon structures have diverse structural diversity due to their various hybridization modes,which brings about the diversity of properties of two-dimensional carbon materials.Therefore,two-dimensional carbon structures may have high-performance solar cell materials and are excellent candidates for solar cell materials.In this study,a flat-band-oriented structure design method was used to search for structures suitable for solar cell materials in two-dimensional carbon structures.Through screening for structural stability and band structure,a two-dimensional carbon structure with Pmmm space group was selected as a solar cell material.This structure has characteristics of both diamond and graphite,and is named 2D diaphite.Band structure calculations revealed that 2D diaphite is a semiconductor with a direct bandgap and has the expected flat band characteristics.By combining it with suitable acceptor materials,four types of type-II van der Waals heterostructures were formed.These heterostructures have high photoelectric conversion efficiency.2D diaphite is a potential solar cell material,and it demonstrates that the flat-band-oriented structure search method designed by the authors is an effective method for finding light-absorbing materials.3.Application of light-absorption-guided structure prediction Strategy in photocatalysts for water splittingDue to the increasing demand for renewable energy and environmental protection,photocatalytic water splitting for hydrogen production has received widespread attention.In previous studies,scientists have discovered a series of metal-based photocatalysts with high catalytic activity and efficiency.Although these metal-based photocatalysts have good catalytic activity,their application under acidic conditions is limited by severe corrosion.Corrosion under acidic conditions leads to deactivation and degradation of photocatalysts,resulting in reduced catalytic activity and stability,which is a serious problem for practical applications.To solve this problem,scientists are searching for new photocatalysts,and one possible solution is to develop non-metal-based photocatalysts,such as semiconductor materials.Two-dimensional carbon materials are one of the most suitable candidate materials due to their excellent performance and corrosion resistance brought by carbon elements.Therefore,in this study,a flat-band-oriented structure design method was used to search for materials suitable for photocatalysts for water splitting in two-dimensional carbon structures.After screening for stability,bandgap,and band edge position,two materials suitable for photocatalysts for water splitting were obtained,named 2D tri-hex carbon and2 D 467-carbon.2D tri-hex carbon is a two-dimensional carbon structure composed of threeatom carbon rings and six-atom carbon rings with sp3 and sp2 hybridized bonds.It is worth noting that 2D tri-hex carbon has an appropriate direct bandgap and band edge position for photocatalytic water splitting.Furthermore,the photocatalytic activity of 2D tri-hex carbon for water splitting was verified through the study of the mechanisms of water oxidation and hydrogen reduction half-reactions.In addition,under acidic conditions,2D tri-hex carbon has a high solar-to-hydrogen conversion efficiency,which can meet the requirements for economically producing hydrogen through photocatalytic water splitting.Overall,2D trihex carbon is a promising photocatalyst for water splitting under acidic conditions.2D 467-carbon is a two-dimensional carbon structure composed of four-atom carbon rings,six-atom carbon rings,and seven-atom carbon rings with sp3 and sp2 hybridized bonds.This carbon structure has a direct bandgap and also exhibits flat band characteristics.The photocatalytic activity of 2D 467-carbon for water splitting under acidic conditions was verified through the study of the mechanisms of water oxidation and hydrogen reduction half-reactions.It also has a good absorption coefficient.The authors believe that it is a photocatalyst for water splitting that can work under acidic conditions.This also indicates that the flat-bandoriented structure search method designed by the authors can be applied to the search for photocatalysts for water splitting. |
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