Nitrogen-doped-TiO2 nanocatalyst for selective photocatalytic CO2 reduction to fuels in a monolith reactor

Abstract

In this study, photocatalytic CO₂ reduction with H₂ over nitrogen (N)-doped TiO₂ nanocatalyst in a monolith photoreactor has been investigated. The N-doped TiO₂ nanocatalyst was synthesized by sol-gel method, dip-coated over the monolith channels, and characterized by XRD, SEM and N₂ adsorption-desorption. Highly crystalline and anatase phase TiO₂ was produced in the N-doped TiO₂ samples with increased surface area and reduced crystallite size. The N-doped TiO₂ nanocatalyst demonstrated excellent photoactivity for selective CO₂ reduction to CO in a continuous monolith photoreactor. The 3 wt. % N-doped TiO₂ was found to be the most optimal, giving maximum CO yield rate of 56.30 µmole g-catal.^-1 h^-1 with selectivity of 96.3% at CO₂/H₂ feed ratio 1 and feed flow rate 20 mL/min. The performance of monolithic N-doped TiO₂ nanocatalyst for selective and continuous CO production was 4.7 fold higher than un-doped TiO₂. The significantly enhanced TiO₂ activity was evidently due to hindered charges recombination rate due to N₂ doping. The N-doped TO₂ gave prolonged stability for continuous CO and CH₄ production over the irradiation time.