Dual modulation steering electron reducibility and transfer of bismuth molybdate nanoparticle to boost carbon dioxide photoreduction to carbon monoxide

Owing to the exorbitant CO₂ activation energy and unsatisfactory photogenerated charge separation efficiency, CO₂ photoconversion still faces enormous challenges. In this study, a directional electron transfer channel has been established by decorating N-doped carbon quantum dots (N-CQDs) on the surface of Bi₄MoO₉ nanoparticles to ensure that more active electrons can participate in the CO₂ reduction. The conduction band of Bi₄MoO₉ nanoparticles is calculated to be -1.55 eV versus the normal hydrogen electrode (NHE), pH = 7, which is negative enough to attain the photocatalytic CO₂ reduction potential of -0.53 eV versus NHE, pH = 7. CO₂ adsorption curves and in situ Fourier transform infrared spectra reveal that N-CQDs facilitate surface CO₂ adsorption and activation, as well as CO desorption. In addition, steady-state photoluminescence and photoelectrochemical tests prove that the charge separation efficiency can be greatly enhanced by constructing N-CQDs/Bi₄MoO₉ composites. In the presence of pure water, N-CQDs/Bi₄MoO₉-2 composite achieved a CO yield of 16.22 μmol g^-1 after 5 h Xe light illumination, which was 3.24 times higher than that of pure Bi₄MoO₉ (4.98 μmol g^-1). This study offers a distinctive approach to the optimization of Bi₄MoO₉ photocatalysts and their application in energy conversion.