Comparative study on photocatalytic CO2 reduction performance of modified-TiO2 nanotube arrays

Abstract

The effective conversion of CO₂ into solar fuels using a photocatalytic (PC) technique is one of the most promising strategies to support sustainable energy production and meet the global energy requirements. In this work, with surface modification approach, TiO₂ nanotube arrays (TNTAs) were modified using noble metals (Au, Ag), carbon-based materials (RGO, g-C₃N₄) and MOF (NH₂-MIL-125 (Ti)) for the enhancement of PC CO₂ reduction. The surface of TNTAs was decorated with noble metals using a simple electrochemical deposition approach, while RGO, g-C₃N₄, and MOF were deposited using a dispersion method. Enhanced optical and chemical properties of modified photocatalysts were confirmed by various characterizations. Controlled architecture of TNTAs with excellent morphology was obtained, providing outstanding performance of electron transferring with enhanced sorption process. Compared to pristine TNTAs, the modified TNTAs exhibited significantly improved CO₂ reduction under visible light irradiation. And the composite photocatalyst constructed by the incorporation of g-C₃N₄ showed the highest CO₂ photoreduction with the CO and CH₄ yields of 29.69 and 2.88 µmol/cm²/h, which were 12.5 and 7-times higher that of TNTAs, respectively. The higher CO₂ photoreduction of the g-C₃N₃/TNTAs binary composite was ascribed to the synergistic action between g-C₃N₄ and TNTAs which substantially reduced the band gap energy. The modified-TNTAs' stability and recyclability also showed that there was no discernible change in photocatalytic performance throughout several cycle runs, resulting in continuous CO and CH₄ generation. The encouraging PC activity for CO₂ conversion exhibits that TNTAs photocatalysts modified by carbon-based materials provided a feasible route to boost CO₂ reduction rate utilizing abundant solar light.