Phosphorene is an elemental two-dimensional material that shows great promise as a metal-free photocatalyst owing to its high carrier mobility and direct band gap. Edge atom decoration of phosphorene is regarded as a potential pathway to address the inherent stability concerns of pristine phosphorene under ambient conditions while enabling the tuning of its opto-electronic properties for applications in photocatalysis and photovoltaics. Herein, the electronic and optical properties of a series of edge-passivated monolayer rectangular phosphorene quantum dots are discussed using an array of substituent groups (OH, SH, NH<sub>2</sub>, SCH<sub>3</sub>, OCN, CN, and Cl) that perturb the electron density distribution due to its electron donating or withdrawing capabilities there by inducing polarity in the material at its edges. Density functional theory is employed to demonstrate the resultant perturbative shifts of HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy levels while attributing the relative shifts to the nature of the substituent group and the role it plays in the formation of edge dipole layers. Furthermore, DFT calculations have been used to demonstrate that phosphorene quantum dots encapsulated by graphene quantum dots can be selectively tuned via phosphorene edge functionalization to form type II heterojunctions that satisfy the thermodynamic requirements for both Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) of the water splitting reaction. Our results suggest that selective functionalization permits considerable control over the band edge positions, which could be utilized for applications in energy and optoelectronic devices.

Probing the electrostatic landscape of phosphorene and phosphorene/graphene composites via edge atom passivation for advancements in HER and OER

ACS Fall 2021

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