Nanoarchitectonics of CuNi bimetallic nanoparticles in ionic liquids for LED-assisted synergistic CO2 photoreduction

An efficient and robust photocatalysts have been developed by combining bimetallic CuNi nanoparticles and TiO2. Simple co-reduction of CuCl2.2H2O and NiCl2.6H2O in 1-n-butyl-methylimidazolium tetrafluoroborate (BMIm.BF4) ionic liquid affords small sized (4–5 nm) bimetallic CuNi NPs. Low-Energy Ion Scattering (LEIS) and magnetic measurements analyses reveals that the NPs are alloyed nanostructure-having Ni enriched surface. CuNi NPs decorated on P25-TiO2 remarkably promote the generation of CH3OH and syngas as compared to their monometallic counter-parts using 1200 mW LEDs of 450 nm (visible) light irradiations in an optofluidic microreactor. The system continuously produces CH3OH with a rate of 102.1 μm.g−1.h−1 (AQY 0.90%) and syngas (H2 118.8 and CO 24.6 μmol.g−1.h−1), represents a high yield and quantum efficiency. Where as, its counter-part, Ni/TiO2, generate CH3OH with a rate of 37.0 μm.g−1.h−1, H2 200.0 μmol.g−1.h−1 and CO 15.1 μmol.g−1.h−1 having 0.33, 0.59 and 0.1% AQY, respectively. The presence of Cu in CuNi NPs significantly boosts the catalytic performance via metal dilution and synergistic effect, causes the red shift and increases the conductivity, while Ni increases the band gap, thereby achieving a record high CH3OH rate generation.