Lithium nitrate-assisted hydrothermal synthesis of ultrathin Bi2O2Se nanosheets and their photoelectrochemical performance

Abstract

Two-dimensional Bi₂O₂Se has drawn a lot of attention recently, due to its ultrahigh mobility and excellent performance in electronics and optoelectronics. However, the facile synthesis of two-dimensional Bi₂O₂Se nanocrystals is urgently required for their fundamental study and practical applications. In this work, we develop a controllable synthetic route to ultrathin Bi₂O₂Se nanosheets through the assistance of lithium nitrate (LiNO₃) in a hydrothermal process. TEM, AFM, XRD, XPS and Raman demonstrate the successful synthesis of ultrathin Bi₂O₂Se nanosheets with a tetragonal phase. With Li⁺ adsorbing on {001} facets to inhibit crystal growth along the [001] direction, the lateral size of the Bi₂O₂Se nanosheets can be controlled through the amount of LiNO₃ in the system. Photoelectrochemical tests reveal the good performance of the ultrathin Bi₂O₂Se nanosheets as a photoanode material in neutral solution. Detailed analysis of electrochemical impedance spectra and specific surface areas reveals that a high surface area and low recombination rate are responsible for the good photoelectrochemical activity of the larger Bi₂O₂Se nanosheets. Besides, the stability test shows negligible reduction of current density after 10 hours, and the TEM test demonstrates that the structure of the Bi₂O₂Se nanosheets is well preserved after long-term electrolysis, revealing great stability of the Bi₂O₂Se nanosheets as a photoanode material. This work indicates that two-dimensional Bi₂O₂Se could be a competitive candidate for the future energy systems.