LAUSR

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.