Stearic acid-TiO2 composite Janus sheets perpendicular to the interface for emulsification and photocatalysis

• Novel 2D TiO 2 Janus sheets (V-STA-TiO 2 JNs) with different structures and properties at each side of the same plane were designed and prepared via a simply and easily operated impregnation method. • V-STA-TiO 2 JNs can be used as emulsifier to prepare Pickering emulsion and existed vertically at the oil–water interface. • V-STA-TiO 2 JNs have better emulsifying effect and more effective catalytic effect than the traditional Janus sheet emulsifiers, and their self-degradation can be ignored. Novel 2D Janus sheets with stearic acid (STA) at one side and TiO 2 at the other side of the same plane, which were called vertical STA-TiO 2 Janus sheets (V-STA-TiO 2 JNs), were prepared via a simply and easily operated impregnation method. Dispersion behavior and contact angle both demonstrated that V-STA-TiO 2 JNs were amphiphilic. V-STA-TiO 2 JNs can be used as emulsifier to prepare Pickering emulsion and existed vertically at the oil–water interface observed by polarized optical microscope (POM). Emulsion stabilized by V-STA-TiO 2 JNs showed better stability than that by traditional STA-TiO 2 Janus sheets (STA-TiO 2 JNs). V-STA-TiO 2 JNs showed higher catalytic activity in photocatalytic degradation of nitrobenzene (NB) and kerosene in wastewater. ·OH radicals were confirmed to be the main active species and played a dominant role in NB degradation under irradiation and the photocatalytic mechanism were discussed. The method also provides new insights for the future research on Janus materials.