Energy Conversion Mechanism Of Low Dimensional Noble Matel Free Structure New Energy Materials At Atomic Level

As the energy crisis and environmental pollution escalate further,there is urgent need for green and clean energy to meet daily production and life.Nanomaterials have excellent electrical,optical and mechanical properties.The research of low-dimensional nanomaterials paves a novel way for the development of new energy sources.In this paper,we apply the low dimensional nano materials in hydrogen energy and piezoelectric energy field,and some achievements have been made.Photocatalytic hydrogen production(H₂)catalysed by nano material is a promising technology for generating new energy.In this paper,the water splitting catalyzed by Zn PP-BDP is systematically studied.We detailed analyze the optimal reaction path,electron spin density of states,barrier transfer and proton transfer of the catalysis process.The proton coupled electron sequent transfer possess an essential role in photocatalytic water dissociation.The H₂O/Zn PP in valence state based on the electron transfer pulls the trigger on the water splitting process.For the oxygen evolution reaction(OER)step on Zn PP,the processes for the two H ions dissociate from water are exothermic with the-1.06 and-0.95 e V energies respectively,and the O/Zn PP system is formed.The second H₂O molecule on O/Zn PP system can provide the extra oxygen atom to produce the free O₂with 1.22 e V energy barrier.For the hydrogen evolution reaction(HER)step on BDP,the H ions dissociated from OER process can be captured by BDP to form free H₂ with 2.24 e V/molecule energy released.In this attractive clean cyclic process,the Zn PP-BDP can continuously catalyze the H₂O dissociated into free H₂ and O₂ by the shifting potential barrier.It is very instructive to design sustainable photodecomposition catalysts for both OER and HER,and to design extraordinary biomimetic photosynthesizers for clean energy.Similarly,piezoelectric materials can converse mechanical energy to electrical energy,and the whole process is clean and sustainable.Here,we studied the electronic,mechanical and piezoelectric properties of 2D group IV-V(IV=Si,Ge and Sn;V=N,P and As)monolayers and novel Janus X₂PAs(X=Si,Ge and Sn)piezoelectric monolayers which are designed based on 2D group IV-V monolayers.The density functional theory(DFT)calculation shows that the 2D group IV-V(IV=Si,Ge and Sn;V=N,P and As)monolayers have obvious semiconductor properties.Elastic coefficients show that these monolayers meet the stability criteria of 2D hexagonal material,and the mechanical properties of these 2D group IV-V compounds are relatively flexible except Si N.All group IV-V monolayers show obvious in-plane piezoelectric effect due to the lack of inversion symmetry along x direction.The piezoelectric coefficient shows certain periodicity.Sn N possess the largest in-plane piezoelectric coefficient|d₁₁|=1.93 pm/V,which reaches the same order of magnitude as Mo S₂.The DFT calculation shows the Janus X₂PAs monolayers are stable and extremely flexible.These monolayers exhibit piezoelectric effect in both in-plane and out-of-plane.Especially,among them,the Sn₂PAs monolayer has the largest piezoelectric coefficient|d₃₁|(1.42 pm/V)that is two times larger than the|d₃₁|of group III–V buckled honeycomb(Ga P,Ga As,In P and In As)monolayers(0.40?0.74 pm/V)and Mo SO monolayer(0.7 pm/V).These facts are due to an inversion symmetry breaking(along the out-of-plane direction)in both atomic structures and charge distribution of X₂PAs monolayers.The out-of-plane piezoelectric and flexible characters of these 2D Janus X₂PAs monolayers could enhance their performance in multifunctional sensing and controlling of the nanodevices.The piezoelectric properties in these monolayers endow them potential applications in energy harvester system and(nano)motor system.In this paper,the organic nano photocatalyst Zn PP-BDP can effectively catalyse the water splitting.The complete decomposition of water into free H₂ and O₂ can be achieved under the mechanism of proton-coupled electron sequent transfer and potential barrier transfer,and the whole process is green and sustainable.The electronics,mechanical flexibility and significant in-plane(out-of-plane)piezoelectric properties of 2D group IV-V monolayers and Janus X₂PAs monolayers provide potential opportunities for their applications in energy harvester system and nanogenerator.