Defects investigation of bipolar exfoliated phosphorene nanosheets

Two-dimensional (2D) phosphorene has gained attention due to its exceptional chemical, physical, and optoelectronic properties. However, defects analysis in exfoliated phosphorene through experimental techniques is still largely missing. In this paper, a combination of high-resolution transmission electron microscopy (HRTEM) imaging and density functional theory calculations were provided to study the point defects, grain boundaries (GBs), and amorphization phenomenon in exfoliated phosphorene nanosheets via bipolar electrochemistry method. The HRTEM results demonstrate that the single vacancies (SV) and di-vacancies (DV), ad-atoms, and GBs defects are formed in phosphorene nanosheets. However, the exfoliated black phosphorus nanosheets maintained its orthorhombic crystal structure. In addition, amorphization on the edges and surface of nanosheets is unavoidable in the presence of oxygen. Our first-principles simulation confirms the breakage of P-P bonds of phosphorene upon surface oxidation, which results in amorphization. The defect analysis of phosphorene nanosheets obtained from this study could benefit both fundamental research and technological applications.