Photocatalytic butanol reforming for hydrogen production using Ag2O/TiO2 composite catalysts: effects of Ag2O loading, calcination temperature, and reaction parameters

Abstract

Over recent years, photocatalytic biomass reforming for hydrogen production has gained research attention as an alternative to the inefficient water-splitting reaction, which requires a standard Gibbs free energy of 237 kJ mol⁻¹. In this study, anatase-phase titanium dioxide (TiO₂) particles were successfully synthesized by employing a sol–gel method, and silver oxide (Ag₂O) nanoparticles with different weight percentages were loaded on the surface of TiO₂ via an incipient wet impregnation method to form composite photocatalysts. The structural and optical properties, specific surface areas, and morphology of the photocatalysts were investigated using X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (FESEM) analyses. The photocatalytic hydrogen activity of the prepared photocatalysts was studied under visible light irradiation, and it was found that varying the Ag₂O loading influenced this activity. Furthermore, it was found that the calcination temperature and reaction parameters, such as pH and initial butanol concentration, influenced the photocatalytic activity of the prepared photocatalysts for efficient hydrogen production. The highest photocatalytic hydrogen production efficiency was achieved with 0.5 wt% Ag₂O/TiO₂ composite photocatalyst (290 mmol g_cat⁻¹). This activity was attributed to 100% anatase crystallite TiO₂ particles that are highly active in terms of the photogeneration of charge carriers; the uniform distribution of Ag₂O on the TiO₂ surface enhanced the suppression of charge-carrier recombination. Finally, the slightly acidic conditions of the butanol mixture facilitated the efficient adsorption of butanol on the surface of the photoexcited photocatalysts, resulting in the simultaneous rapid oxidation of butanol and the efficient production of hydrogen molecules.