Selective photo-reduction of CO2 to methanol using Cu-doped 1D-Bi2S3/rGO nanocomposites under visible light irradiation

A novel Cu-doped one dimensional (1D) Bi2S3 rod-shaped nanocapsule/rGO composite is explored as a photocatalyst for selective reduction of CO2 to methanol. In particular, the effects of Cu doping of rGO supported Bi2S3 on band gap tuning and on product selectivity are investigated. Bi2S3 rod-shaped nanocapsules and 0.5, 1, and 2 weight percent Cu-doped Bi2S3/rGO are synthesised through a hydrothermal approach. The photocatalysts are characterized by XRD, FTIR, UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and SEM, TEM and EDX analysis. It is revealed that Cu-doped Bi2S3/rGO for all different compositions offers selective and enhanced production of methanol compared to undoped Bi2S3/rGO, pristine Bi2S3, and Cu-doped Bi2S3 which produce formic acid along with methanol. The optimum 1 weight percent Cu-doped Bi2S3/rGO photocatalyst, exhibiting the smallest band gap and the lowest rate of recombination of electron-hole pairs, offers the highest photocatalytic activity of 719 mu mol g(cat.)(-1) h(-1). DFT studies corroborate the experimental finding of a drastic reduction of the band gap (1.36 eV) of Cu-doped Bi2S3/graphene and unveil that Cu 3d-C 2p hybridization as well as enhancement of Bi 6p-C 2p hybridization in the presence of copper significantly increases the overall DOS of the system at the Fermi level, resulting in enhancement of electronic conductivity and charge transfer; further deformation in the graphene sheets due to the presence of Cu-Bi2S3 creates CO2 trapping sites for its efficient adsorption and selective photoreduction.

Automated summary

A novel Cu-doped Bi2S3/ graphene composite photocatalyst is synthesized and investigated for selective and enhanced production of methanol through the reduction of CO2. The Cu doping effect on band gap tuning and product selectivity is explored. The optimized 1 wt% Cu-doped Bi2S3/graphene photocatalyst exhibits the highest photocatalytic activity. DFT studies confirm the experimental findings and reveal the mechanism of enhanced performance.