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

The effective conversion of CO 2 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, TiO 2 nanotube arrays (TNTAs) were modified using noble metals (Au, Ag), carbon-based materials (RGO, g-C 3 N 4 ) and MOF (NH 2 -MIL-125 (Ti)) for the enhancement of PC CO 2 reduction. The surface of TNTAs was decorated with noble metals using a simple electrochemical deposition approach, while RGO, g-C 3 N 4 , 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 CO 2 reduction under visible light irradiation. And the composite photocatalyst constructed by the incorporation of g-C 3 N 4 showed the highest CO 2 photoreduction with the CO and CH 4 yields of 29.69 and 2.88 µmol/cm 2 /h, which were 12.5 and 7-times higher that of TNTAs, respectively. The higher CO 2 photoreduction of the g-C 3 N 3 /TNTAs binary composite was ascribed to the synergistic action between g-C 3 N 4 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 CH 4 generation. The encouraging PC activity for CO 2 conversion exhibits that TNTAs photocatalysts modified by carbon-based materials provided a feasible route to boost CO 2 reduction rate utilizing abundant solar light.