Photocatalytic CO2-hydrogen conversion via RWGSR over Ni/TiO2 nanocatalyst dispersed in Layered MMT Nanoclay

Abstract

The production of cleaner fuels from renewable and safer energy resources are highly demanding to mitigate energy crises and global warming. In this study, the use of cleaner photo-technology for selective and enhanced CO2 reduction to fuels over nickel (Ni) modified titanium dioxide (TiO2) dispersed in structured montmorillonite (MMT) nanoclay for photocatalytic CO2-hydrogen conversion via reverse water gas shift (RWGS) reaction has been investigated. The catalyst samples, prepared by a single step sol-gel method, were characterised by XRD, FTIR, FESEM and UV-visible spectroscopy. XRD results revealed reduced in TiO2 crystallite size with Ni and MMT loading and produced anatase phase of TiO2. MMT is found efficient for the enhanced dispersion of TiO2 while Ni-promoted efficient charges separation with hindered recombination rate over the structured MMT/TiO2 nanocomposite. The photoactivity of Ni/TiO2-MMT composite for CO2 reduction was conducted in a continuous flow photoreactor using hydrogen as the reducing agent. The main products detected were CO and CH4 with appreciable amounts of C2H4, C2H6 and C3H6 hydrocarbons. The maximum yield of CO produced as the main product over 3 wt% Ni-10 wt% MMT/TiO2 catalyst was 9,429 µmole/g-cat, 209-fold higher than the amount of CO detected over the pure TiO2. Evidently, Ni-promoted TiO2 photocatalytic activity, while MMT is favourable for improved dispersion of Ni/TiO2 catalyst. The dynamic and selective CO evolution was evidently due to efficient light distribution, enlarged active surface area and efficient charges separation with their hindered recombination rate by Ni and MMT. The stability of Ni/TiO2 dispersed over MMT sustained over the irradiation time. With the use of green nanocomposite catalyst, CO2 can be efficiently converted to cleaner fuels with all sustainable systems.