First-principles Study On Photocatalytic Water Splitting Of InTe/Bismuthene And PtI₂/Bi₂X₃（X=S,Se,Te） Two-dimensional Materials For Hydrogen Production

The development of clean and renewable energy sources is one of the important means to achieve the goal of carbon peaking and carbon neutrality.Hydrogen energy has been proven to be a clean and efficient energy source,and therefore related research has received much attention.In recent years,breakthroughs have been made in the use of sunlight photocatalytic hydrogen generation from water splitting driven by semiconductors,which has led to increased energy efficiency and interest in photocatalytic hydrogen production.However,due to the limitations in the exploration of the mechanism of photocatalytic hydrogen resolution,there are still few semiconductor materials for solar photocatalytic overall water splitting to manufacture hydrogen with high solar-to-hydrogen efficiency.The discovery or design of new solar photocatalytic overall water splitting to manufacture hydrogen materials remains at the forefront of hydrogen energy research.In recent years,two-dimensional materials have shown good performance in photocatalysis due to their large specific surface area and unique electronic structure,especially the special mechanism of heterostructure can enhance the solar-to-hydrogen efficiency,which has attracted the attention of many researchers.In this paper,the electronic structure,optical properties,solar-to-hydrogen efficiency and Gibbs free energy of two-dimensional InTe/Bismuthene and PtI₂/Bi₂X₃（X=S,Se,Te）heterostructures are calculated based on first principles to explore their feasibility as semiconductor materials for solar photocatalytic overall water splitting to manufacture hydrogen.The main contents are as follows:1.The stable configurations of two monolayers,InTe and Bismuthene,were determined to form InTe/Bismuthene heterostructure.Nine configurations were constructed by rotating and stacking each monolayer in different directions while maintaining a suitable lattice mismatch rate,and the three most stable configurations were determined by calculating the binding energy.The thermodynamic stability was confirmed using ab initio molecular dynamics simulations.Calculations of the electronic structure properties showed that both the band alignments and the built-in electric field satisfied the requirements of the overall water splitting to generate hydrogen with the Z-scheme.The optical properties,solar-to-hydrogen efficiency,Gibbs free energy and strain engineering of the three configurations were then investigated.The results show that their solar-to-hydrogen efficiency can reach a maximum of 9.67%,which is better than the4.22%of the InTe monolayer composing it,indicating that the photocatalytic performance of the monolayer can be effectively improved by forming a heterostructure.The strain has an effect on both band edges and bandgaps of the two monolayers composing the heterostructure,thus changing their optical absorption and overpotential.The maximum solar-to-hydrogen efficiency of the InTe/Bismuthene heterostructure was increased to16.17%at 9%tensile strain.The change in Gibbs free energy for the hydrogen evolution reaction ranges from 1.72 to 2.12 e V,which is smaller than the 2.7 e V of the Ni₃S₂ system that has been experimentally demonstrated to drive the hydrogen evolution reaction,indicating the thermodynamic feasibility of the hydrogen evolution reaction in the InTe/Bismuthene heterostructure.These results suggest that this heterostructure can be used as a potential material for solar photocatalytic overall water splitting to manufacture hydrogen.2.The photocatalytic performance of PtI₂ and Bi₂X₃（X=S,Se,Te）monolayers was analyzed computationally,and it was found that Bi₂X₃（X=S,Se,Te）monolayers did not meet the band edge requirement for sunlight photocatalytic hydrogen generation from water splitting,and PtI₂ monolayers met the requirement but the photocatalytic efficiency was not satisfactory.Therefore,PtI₂/Bi₂X₃（X=S,Se,Te）heterostructures were constructed to further improve the solar-to-hydrogen efficiency.From the possible stacking methods of PtI₂ and Bi₂X₃（X=S,Se,Te）monolayers satisfying the lattice mismatch rate,the three most stable configurations were selected based on the binding energy calculation results.The electronic structure properties were calculated after confirming their thermodynamic stability by ab initio molecular dynamics simulations.The results show that the energy band alignments and the built-in electric field of the PtI₂/Bi₂S₃ and PtI₂/Bi₂Se₃ heterostructures match the conditions of the overall water splitting to generate hydrogen with the Z-scheme,while it is found that the built-in electric field of the PtI₂/Bi₂Te₃ heterostructure only supports the type II,but its-5.51 e V valence band maximum cannot satisfy the requirement of the potential conditions for the oxygen evolution reaction in the sunlight photocatalytic hydrogen generation from water splitting.Therefore,the next discussion on the photocatalytic performance focuses on PtI₂/Bi₂S₃and PtI₂/Bi₂Se₃ heterostructures.The solar-to-hydrogen efficiency and Gibbs free energy were calculated and analyzed to quantitatively assess their photocatalytic performance and thermodynamic feasibility.The solar-to-hydrogen efficiency of the two heterostructures can reach up to 16.36%and 18.23%,respectively,and can be increased to 24.77%and 22.48%under appropriate strain conditions.The Gibbs free energy change maxima of the two heterostructures driven hydrogen evolution reaction are 1.58 e V and0.92 e V,respectively,which are both smaller than the experimentally achievable range.Therefore,the hydrogen evolution reaction with the direct Z-schemes driven by the PtI₂/Bi₂S₃ and PtI₂/Bi₂Se₃ heterostructures are feasible in thermodynamic.All the results show that although PtI₂/Bi₂Te₃ heterostructure does not satisfy the conditions for sunlight photocatalytic hydrogen generation from water splitting,both PtI₂/Bi₂S₃ and PtI₂/Bi₂Se₃heterostructures can be used as candidates for driving high solar-to-hydrogen efficiency for sunlight photocatalytic hydrogen generation from water splitting.