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.