Strain Engineering for Phosphorene: The Potential Application as a Photocatalyst

Abstract: Phosphorene has been attracted intense interest due to its unexpected high carrier mobility and distinguished anisotropic optoelectronic and electronic properties. In this work, we unraveled strain engineered phosphorene as a photocatalyst in the application of water splitting hydrogen production based on density functional theory calculations. Lattice dynamic calculations demonstrated the stability for such kind of artificial materials under different strains. The phosphorene lattice is unstable under compression strains and could be crashed. Whereas, phosphorene lattice shows very good stability under tensile strains. Further guarantee of the stability of phosphorene in liquid water is studied by ab initio molecular dynamics simulations. Tunable band gap from 1.54 eV at ambient condition to 1.82 eV under tensile strains for phosphorene is evaluated using parameter-free hybrid functional calculations. Appropriate band gaps and band edge alignments at certain pH demonstrate the potential application of phosphorene as a sufficiently efficient photocatalyst for visible light water splitting. We found that the strained phosphorene exhibits significantly improved photocatalytic properties under visible-light irradiation by calculating optical absorption spectra. Negative splitting energy of absorbed H2O indicates the water splitting on phosphorene is energy favorable both without and with strains.

• The paper demonstrates that tensile strain improves phosphorene’s structural stability and tunes its band gap from 1.54 to 1.82 eV for visible light absorption.
• It employs density functional theory and HSE06 hybrid calculations to precisely predict optimal band edge alignments for effective water splitting at pH 8.0.
• The findings underscore the potential of strain engineering to enhance photocatalytic efficiency, paving the way for advanced hydrogen production systems.

Strain Engineering for Phosphorene as a Photocatalyst: An Overview

This paper focuses on the investigation of the potential of strain-engineered phosphorene as an efficient photocatalyst for water splitting applications. Employing density functional theory (DFT) calculations, the authors explore the structural stability, electronic properties, and photocatalytic capabilities of phosphorene under various strain conditions.

The discovery of phosphorene, a two-dimensional material composed of a single layer of black phosphorus, has opened new opportunities in material science due to its distinct anisotropic electronic and optoelectronic properties, along with its high carrier mobility. While much research has focused on graphene and related materials for photocatalytic applications, phosphorene has emerged as a compelling candidate because of its adjustable band gap properties and pronounced sensitivity to strain.

Computational Analysis and Methodologies

Density functional theory (DFT) calculations were conducted using the Vienna ab initio simulation package, employing projector augmented wave pseudopotentials within the generalized gradient approximations framework. Hybrid functional calculations, including the Heyd-Scuseria-Ernzerhof (HSE06) method, were utilized to accurately predict band gaps and band edge alignments. Such calculations are critical for assessing the semiconductor properties of phosphorene relative to water splitting requirements, specifically ensuring that the conduction band minimum (CBM) and valence band maximum (VBM) align appropriately with redox potentials.

Structural Stability Under Strain

Phosphorene’s structural stability was evaluated under a range of tensile and compressive strains along its principal axes. The material demonstrates remarkable stability under tensile strains, but is predicted to be dynamically unstable under compressive strains due to the appearance of imaginary frequencies in phonon dispersion curves. This instability precludes the use of compressively strained phosphorene in photocatalytic applications. Conversely, the tensile strain not only improves structural integrity but also optimizes the electronic band structure for enhanced photocatalytic performance.

Electronic Properties and Photocatalysis Potential

Strain engineering reveals a tunable band gap for phosphorene, ranging from 1.54 eV in its natural state to 1.82 eV under tensile strain conditions. These band gaps are ideal for efficient visible light absorption. The band edge alignments under different pH conditions suggest that phosphorene can function as a suitable photocatalyst for water splitting, specifically at elevated pH levels (e.g., pH 8.0), where the oxidizing and reducing powers align well with the necessary redox potentials.

Photocatalytic Efficiency and Future Outlook

The calculated optical absorption spectra indicate that strain can significantly enhance the visible light absorption capacity of phosphorene. This enhancement fosters improved photocatalytic efficiency, making strained phosphorene a promising material for hydrogen production via water splitting. The paper's findings underscore the importance of strain engineering in tailoring the properties of two-dimensional materials like phosphorene for specific applications.

The study has broader implications for the development of advanced photocatalytic systems and provides a framework for exploring similar enhancements in other two-dimensional materials. Future research may build upon these findings to develop more robust and efficient photocatalytic systems that operate over a wider range of environmental conditions.

In conclusion, the systematic exploration of strain effects on phosphorene's properties as presented in this paper contributes significant insights into the design of efficient photocatalytic materials. The results advocate for continued research into strain-engineering techniques to further optimize the material's performance in real-world applications.