Influence of surface modification of zinc oxide–based nanomaterials on the photocatalytic reduction of carbon dioxide

• Published in: Materials today chemistry 2021-06, Vol.20, p.100446, Article 100446
• Main Authors: Mgolombane, M., Majodina, S., Bankole, O.M., Ferg, E.E., Ogunlaja, A.S.
• Format: Article
• Language: English
• Subjects: CH3OH; Co-doped ZnO; Co-doped ZnO/rGO; CO2; Photocatalysis
• ISSN: 2468-5194; 2468-5194
• DOI: 10.1016/j.mtchem.2021.100446

ZnO (Z-1), Co-doped ZnO (Z-2), and Co-doped ZnO/rGO (Z-3) nanocomposites are successfully synthesized using a solvothermal method and investigated toward the photoreduction of CO2 to CH3OH. The as-prepared ZnO (Z-1), Co-doped ZnO (Z-2), and Co-doped ZnO/rGO (Z-3) nanomaterials are characterized by a range of spectroscopic, imaging, and thermal techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis, thermogravimetry analysis-differential thermal calorimetry, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, and transmission electron micrograph. It was found that Z-3 presented a higher CH3OH rate of 30.1 μmol/g compared with Z-2 (27.3 μmol/g) and Z-1 (7.5 μmol/g). Enhanced catalytic activity of Z-3 over other samples was because of the combined effect of the amount of Co, reduced graphene (rGO), and surface area (10.62 m2/g). Theoretical calculation revealed that photocatalytic activity has some relationship with the ELUMO = −2.922 eV (doped ZnO). The results can not only provide an important indication about the influence of Co and rGO on the activity of CO2 photoreduction over ZnO but also demonstrate a strategy for tuning the CO2 photoreduction performance. Our work may lay the groundwork for directing the future design of efficient metal-modified ZnO photocatalysts for CO2 reduction. •Successful synthesis of ZnO, Co-doped ZnO, and Co-doped ZnO/rGO.•Successful photocatalytic reduction of CO2.•Density functional theory revealed that doping ZnO facilitated the formation of adsorbed carbonate or CO2.•- species.•Excellent conversion of CO2 to CH3OH of up to 30.1 μmol/gcat with Co-doped ZnO/rGO.