Structural and optical investigation of Nb5+-doped Sn3O4 for photoelectrochemical hydrogen production

We report herein, the microwave-assisted hydrothermal (MAH) synthesis of Nb⁵⁺-doped Sn₃O₄ nanoparticles for the photoelectrochemical production of hydrogen (H₂). Nb⁵⁺ ions inside the Sn₃O₄ created structural defects, contributing to a local structural disorder, as confirmed by micro-Raman spectra. Photoluminescence spectroscopy indicated the decrease of the violet-blue–green visible emission after adding Nb⁵⁺, revealing the formation of alternative energy pathways for the electron/hole recombination. Through the morphological analysis, it was observed that the Nb⁵⁺ dopant slightly changed the morphology of nano-petals in Sn₃O₄. We demonstrate that the 3 % Nb⁵⁺ doped-Sn₃O₄ photoanode presented higher charge carrier mobility, higher photocurrent density, and an impressive H₂ production of 1.50 mmol L⁻¹ in a 3 h experiment, compared to the pure Sn₃O₄ material. The best performance of the Nb⁵⁺ doped Sn₃O₄ nanomaterial could be ascribed to the formation of new energy levels in the Sn₃O₄ band gap, thereby inhibiting the electron-hole pair recombination and positively affecting the photoelectrochemical response of the doped material.