Kržmanc, Marjeta MačekMarjeta MačekKržmancDaneu, NinaNinaDaneuKamal, Khaja MohaideenKhaja MohaideenKamalLikozar, BlažBlažLikozarČontala, AljaAljaČontalaSpreitzer, MatjažMatjažSpreitzerJEFFREY CHI-SHENG WUGupta, SurajSurajGupta2026-01-152026-01-152026-01-0113858947https://www.scopus.com/record/display.uri?eid=2-s2.0-105025103816&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/735365The Aurivillius-Phase Bi₄Ti₃O₁₂ platelets are not only important functional materials in their own right, but also serve as valuable two-dimensional (2D) templates for converting into 2D ATiO₃ (A = Sr, Ba, Ca) perovskite platelets with a favourable (100) orientation. The transformation under low-temperature (200 °C) hydrothermal conditions has recently been demonstrated; however, the process remains underexplored regarding the mechanistic control of the final product properties. This study sheds light on the steering of the Bi₄Ti₃O₁₂-to-SrTiO₃ hydrothermal transformation to precisely control the surface roughness and photocatalytic properties of the 2D epitaxial heterostructural SrTiO₃/Bi₄Ti₃O₁₂ and SrTiO₃ nanoplatelets. A higher excess of Sr (Sr/Ti = 15), smaller Bi₄Ti₃O₁₂ template nanoplatelets, and pre-reaction etching of the template with hot NaOH promote the formation of high-surface-area SrTiO₃/Bi₄Ti₃O₁₂ and SrTiO₃ nanoplatelets (BET >60 m2/g), which show more than 50 times higher H₂ evolution rates compared to smooth, low surface area platelets (BET~10 m2/g). This study demonstrated that higher surface roughness facilitates effective surface trapping of bismuth species, which, through in-situ reduction to metallic Bi° single atoms, acted as a co-catalyst and enhanced photocatalytic H2 evolution. Both SrTiO₃/Bi₄Ti₃O₁₂ and SrTiO₃ nanoplatelets exhibited stable photocatalytic responses, but only SrTiO₃ maintained structural and chemical integrity under illumination. This study presents a new strategy for engineering the surface and functional properties of 2D SrTiO₃ perovskite nanoplatelets through the hydrothermal transformation of Aurivillius phase Bi₄Ti₃O₁₂ nanoplatelets, thereby expanding possibilities for the functional engineering of other 2D perovskite nanostructures.trueAurivillius phase Bi4Ti3O12Hydrothermal transformationPhotocatalytic H2 generationSrTiO3 nanoplateletsjournal article10.1016/j.cej.2025.1717582-s2.0-105025103816