A SnWO4/Ti3C2Tx/polyaniline heterojunction photoelectrode for Cr(vi) detoxification: mechanism investigation by XPS analysis and energy efficiency considerations

Abstract

Chromium (Cr), as a highly mobile, oxidizing, and carcinogenic anionic heavy metal contaminant, poses significant biological health risks and environmental challenges. In this study, a SnWO₄/MXene/polyaniline (SWOMP) heterojunction was synthesized through electrophoretic self-assembly, integrating polyaniline (PANI)-assisted SnWO₄/Ti₃C₂T_x MXene onto a stainless steel mesh support. The multiple functional groups and high electron transfer efficiency of the resulting material enable it to effectively adsorb and photoelectrocatalytically (PEC) reduce the hazardous Cr(VI) to less toxic Cr(III). This intercalation improved the structural synergy and mitigated the over-negative potential of SnWO₄/MXene composites. The SWOMP heterojunction exhibited remarkable enhancements in light absorption, charge separation, and electron transfer, resulting in exceptional PEC activity under visible light irradiation. X-ray photoelectron spectroscopy (XPS) and PEC analyses were employed to elucidate interfacial interactions and charge transfer mechanisms. XPS data confirmed the Cr(VI) adsorption and its reduction processes, suggesting that the adsorption mechanism likely involves multilayer chemisorption, including reduction reactions, electrostatic interactions, and complexation. These features contributed to an impressive Cr(VI) reduction efficiency, achieving complete detoxification (100%) within just 10 min. This outstanding performance is attributed to the ability of the well-designed heterojunction to suppress charge recombination and enhance charge carrier mobility. The study underscores the potential of integrating metal oxide semiconductors and MXene sensitizers into a π-conjugated polymer matrix for developing robust and sustainable materials for environmental remediation. Moreover, it highlights the importance of interfacial engineering in advancing photocatalytic technologies.