Bismuth-Based BiOBr_xI_1–x/Ti₃C₂ MXene Schottky Nanocomposites for Hg²⁺ Photoelectrochemical Sensors

Abstract

BiOBr x I 1−x /Ti 3 C 2 Schottky heterojunction nanocomposites were prepared through a simple electrostatic adsorption and self-assembly method. The Schottky heterojunction was used as a sensitive material in the fabrication of a photoelectrochemical (PEC) sensor for mercury ion detection. Due to the large specific surface area, excellent electrical conductivity, and abundant surface chemical groups of the 2D nano Ti 3 C 2 in the Schottky heterojunction, the in situ growth of solid solution BiOBr x I 1−x on its surface enabled the nanocomposites to form a high Schottky barrier to improve the sensitivity of the PEC response. The addition of glutathione (GSH) caused it to adhere to the surface of the nanocomposites where it hindered the transfer of electrons and reducing the photocurrent by reacting with the bismuth ions on their surface through its carboxyl groups. During the Hg 2+ assay, Hg 2+ ions reacted to GSH on the surface of the heterojunction nanocomposites, and then captured more GSH in a solution to form a complex with 3D structure. This complex further hindered electron transfer and led to a sharp decrease in photocurrent. A trace amount of Hg 2+ was detected based on the change of photocurrent, with a linear range of 1.0 × 10 −10 mol/L to 1.0 × 10 −6 mol/L and a detection limit of 4.21 × 10 −11 mol/L. This method was one of the most sensitive methods reported for Hg 2+ detection. The sensor had been applied to determine trace mercury in environmental water samples.

Recent advances in photoelectrochemical platforms based on porous materials for environmental pollutant detection

“…For instance, Xiao et al prepared BiOBi x I 1− x /Ti 3 C 2 MXene Schottky heterojunction nanocomposites using an electrostatic self-assembly method. 202 Porous Ti 3 C 2 MXene possesses a high specific surface area, excellent electrical conductivity, and an abundance of surface chemical groups. In addition, the Schottky heterojunction of Ti 3 C 2 MXene and BiOBi x I 1− x significantly enhances the separation rate of photogenerated charge pairs, resulting in a higher photocurrent signal compared to BiOBi x I 1− x alone.…”

Real-Space Observation of an In Situ-Built Schottky Junction in a Two-Dimensional MXene Layer

“…), Ti 3 C 2 T x MXene is the most popular 2D material because of its easy delamination into a monolayer by HF treatment, which can help to explore the real 2D characteristics of MXene. Pristine Ti 3 C 2 MXene is expected to form a Schottky junction with semiconductors, which is usually formed at the semiconductor–metal interface by utilizing the difference in the work function of metal and semiconductor. − Several studies showed that conductive Ti 3 C 2 MXene can effectively promote the photocatalytic performance of TiO 2 , ZnO, CeO 2 , g-C 3 N 4 , CdS, Bi 2 S 3 , and ternary semiconductors by superior interface engineering. − The enhanced catalytic activity of TiO 2 is mainly due to the efficient separation of charge carriers at the heterojunctions formed between Ti 3 C 2 T x and TiO 2 . ,− Unlike conventional metallic materials, 2D Ti 3 C 2 MXene used as a gas-sensing metal reveals excellent performance by modulation of in situ-built Ti 3 C 2 –TiO 2 Schottky barriers within the sensing channel. − Likewise, the rutile TiO 2 nanoparticles obtained from Ti 3 C 2 MXene oxidations are proven to be beneficial for the electron transporting layer in perovskite solar cells owing to their excellent defect and trap-assisted recombination suppression properties at the interface. , …”