Manipulating the morphology and charge accumulation driven- Schottky functionalized type II-scheme heterojunction for photocatalytic hydrogen evolution and SERS detection

Abstract

Inspired by energy conversion and sensing strategies, the construction of a type-II heterojunction proves advantageous in enhancing interfacial charge transfer, redox capabilities, and sensitive detection. Herein, we have developed as-prepared a hierarchical heteronanostructure composed of 2D ultrathin g-C3N4 (g-CN) nanosheets, 3D SrTiO3 (STO) nanocubes, and Ag plasmonic nanoparticles (NPs) with a well-controlled configuration and intimate contact for improved practical applications. This multifunctional heterojunction not only exhibits outstanding hydrogen evolution reaction (HER) performance but also shows excellent SERS detection. The creation of hybrid morphologies and type II schemes contributes to expanding visible light absorption and shortening the path of charge carrier transition. The ternary sample also exhibits an efficient photocatalytic HER rate of 9378 μmol g−1 h−1, which is 13.3 and 26.3 times higher than that of STO (703 μmol g−1 h−1) and g-CN (356 μmol g−1 h−1), respectively. Photoluminescence spectroscopy and linear sweep voltammetry (LSV) measurements suggest that the synergistic effect among g-CN nanosheets, STO nanocubes and Ag contributes to enhanced charge separation, as indicated by the applied potential of −0.9 V vs. saturated Ag/AgCl to obtain a photocurrent density of −15 mA cm−2 for the HER. The obtained STO/g-CN/Ag sample exhibits significant capability in enriching small molecules, facilitating the determination of organic pollutants even at ultralow concentrations. Additionally, it exhibits impressive SERS sensitivity and photocatalytic performance. Crystal Violet (CV) at low concentrations can be distinguished and undergoes almost complete degradation under visible-light illumination. The detection platform exhibits ultralow detection capability down to 10−10 M for CV. The outstanding SERS detection may be assigned to the combined enrichment abilities of g-CN, STO and the localized surface plasmon resonance (LSPR) of Ag NPs. Furthermore, the type-II heterojunction of the ternary photocatalyst and the mechanisms governing charge carrier flow and transfer on the conductive Ag co-catalyst were also investigated. This work provides novel insights and techniques for effectively engineering 3D STO-like semiconductors, facilitating both green energy production and the detection of trace molecules.